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Ethylene production is negatively associated with storage life in sand pear (Pyrus pyrifolia Nakai), particularly at the time of fruit harvest. 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is the rate-limiting enzyme in ethylene biosynthesis and is considered to be important for fruit storage life. However, the candidate ACS genes and their roles in sand pear remain unclear. The present study identified 13 ACS genes from the sand pear genome. Phylogenetic analysis categorized these ACS genes into four subgroups (type I, type II, type III and putative AAT), and indicated a close relationship between sand pear and Chinese white pear (P. bretschneideri). According to the RNA-seq data and qRT-PCR analysis, PpyACS1, PpyACS2, PpyACS3, PpyACS8, PpyACS9, PpyACS12 and PpyACS13 were differently expressed in climacteric and non-climacteric-type pear fruits, ‘Ninomiyahakuri’ and ‘Eli No.2’, respectively, during fruit ripening. In addition, the expressions of PpyACS2, PpyACS8, PpyACS12 and PpyACS13 were found to be associated with system 1 of ethylene production, while PpyACS1, PpyACS3, and PpyACS9 were found to be associated with system 2, indicating that these ACS genes have different roles in ethylene biosynthesis during fruit development. Overall, our study provides fundamental knowledge on the characteristics of the ACS gene family in sand pear, in addition to their possible roles in fruit ripening. [ABSTRACT FROM AUTHOR]

Drought imposes stress on plants and associated soil microbes, inducing coordinated adaptive responses, which can involve plant–soil signalling via phytohormones. However, we know little about how microbial communities respond to phytohormones, or how these responses are shaped by chronic (long-term) drought. Here, we added three phytohormones (abscisic acid, 1-aminocyclopropane-1-carboxylic acid, and jasmonic acid) to soils from long-term (25-year), field-based climate treatments to test the hypothesis that chronic drought alters soil microbial community responses to plant stress signalling. Phytohormone addition increased soil respiration, but this effect was stronger in irrigated than in droughted soils and increased soil respiration at low phytohormone concentrations could not be explained by their use as substrate. Thus, we show that drought adaptation within soil microbial communities modifies their responses to phytohormone inputs. Furthermore, distinct phytohormone-induced shifts in microbial functional groups in droughted vs. irrigated soils might suggest that drought-adapted soil microorganisms perceive phytohormones as stress-signals, allowing them to anticipate impending drought. Emma Sayer et al. use a 25-year field experiment to investigate how microbial community responses to phytohormones are affected by drought. Phytohormone-induced shifts in microbial functional groups suggest that drought adaptation within soil microbial communities mediates responses to plant stress signalling. [ABSTRACT FROM AUTHOR]

Rhizosphere provides unique space for intensive chemical conversation between plant and microorganisms. The common rhizobacterial mechanisms which have been demonstrated to promote plant growth include production of phytohormones, nitrogen fixation, synthesis of 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) and phosphate solubilization. The microbially produced phytohormone indole-3-acetic acid (IAA) is considered to have significant role in interaction between plant and bacteria. Hence any substance with modulatory effect on rhizobacterial IAA production can expect to have its impact on plant-microbe interaction. With the advent of nanotechnology, nanoparticles are being used for diverse applications. However, applications of nanotechnology in agriculture have not been studied in detail. In the study, rhizospheric Pseudomonas monteilii was selected to investigate the concentration-dependent effect of biogenic gold nanoparticles (AuNPs) on its IAA production. For this, AuNPs synthesized by Bacillus subtilis SJ15 were characterized by UV-Vis spectroscopy, FT-IR, TEM and EDS. The results showed AuNPs to have spherical, hexagonal and triangular shapes with a size range of 12-32 nm and absorption peak at 545 nm. Further, various concentrations of AuNPs were used to identify its impact on IAA production by P. monteilii. From this, enhanced production of IAA by P. monteilii was found to take place in the presence of 50 µg/mL AuNPs. When Vigna unguiculata seedlings were grown in presence of 50 µg/mL of AuNPs, increased growth was observed. The results of the study thus showed the ability of AuNPs to augment the IAA-producing potential of P. monteilii. [ABSTRACT FROM AUTHOR]

Summary: Ethylene plays a critical role in many diverse processes in plant development. Recent studies have demonstrated that overexpression of the maize ARGOS8 gene reduces the plant's response to ethylene by decreasing ethylene signaling and enhances grain yield in transgenic maize plants. The objective of this study was to determine the effects of ethylene on the development of nodal roots, which are primarily responsible for root‐lodging resistance in maize. Exogenous application of the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC) was found to promote the emergence of nodal roots. Transcriptome analysis of nodal tissues revealed that the expression of genes involved in metabolic processes and cell wall biogenesis was upregulated in response to ACC treatment, supporting the notion that ethylene is a positive regulator for the outgrowth of young root primordia. In BSV::ARGOS8 transgenic plants with reduced ethylene sensitivity due to constitutive overexpression of ARGOS8, nodal root emergence was delayed and the promotional effect of ACC on nodal root emergence decreased. Field tests showed that the BSV::ARGOS8 plants had higher root lodging relative to non‐transgenic controls. When ARGOS8 expression was controlled by the developmentally regulated promoter FTM1, which conferred ARGOS8 overexpression in adult plants but not in the nodal roots and nodes in juvenile plants, the FTM1::ARGOS8 plants had no significant difference in root lodging compared with the wild type but produced a higher grain yield. These results suggest that ethylene has a role in promoting nodal root emergence and that a delay in nodal root development has a negative effect on root‐lodging resistance in maize. Significance Statement: Root‐lodging resistance is a critically important trait for high‐yield maize hybrids and has been selected in maize breeding programs over the past 100 years. In maize, the stem‐borne nodal roots are formed in the normal developmental process and play a major role in root‐lodging resistance. Using the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and ARGOS8 transgenic plants which have reduced ethylene sensitivity, we found that ACC promotes nodal root emergence and that ARGOS8 transgenic plants have delayed nodal root development and increased root lodging. These results suggest a positive role for ethylene in root‐lodging resistance. These findings have applications in maize breeding for improved agronomic traits. [ABSTRACT FROM AUTHOR]

Tulip (Tulipa gesneriana L.) holds spectacular and colorful bright floral buds that are widely adorned like no other flower, across the globe. In cut flowers, persistent and prolonged display life is the matter of concern which decides quality index for florists and consumers. Endophytic bacteria, taken up by the plants when colonized, can act as sink for 1-aminocyclopropane- 1-carboxylate (ACC), hence delay senescence. These bacteria, when used as suspension solution for cut flowers, increase the vase life manifolds which signify their application to commercial floriculture. Keeping in view, the exalted status and market value of cut tulips, an experiment was conducted to study the response of four bacterial strains viz. Burkholderia phytofirmans (PsJN), Caulobacter sp. (FA-13), Enterobacter sp. (MN-17) and Bacillus sp. (MN-54) along with control treatment (nontreated stems) in concentrated and diluted forms to estimate the postharvest longevity. 15 mL of suspension solution of bacterial culture was sprayed on each observational unit under controlled conditions in laboratory. In this experiment, (PsJN) in concentrated form, performed best and resulted in the longest vase life (11.2 d), delayed leaf yellowing (8.8 d), more water uptake (70.33 mL), less stem elongation (5.14 cm), more days to open flower bud (2.47 d), maximum flower diameter (50.79 mm) and. Whereas (MN-17) in concentrated form performed best in fresh and dry mass ratio and reduced stem bending. In conclusion, use of plant growth promoting bacteria (PGPB) is a useful tool in escalating vase life of cut tulips with improved floral attributes. [ABSTRACT FROM AUTHOR]

Plant APETALA2/Ethylene-responsive element binding factor (AP2/ERF) transcription factor involved in various biological functions such as plant development, flower development, fruit and seed maturation, wounding, pathogen defense, high salty, drought, and so on. Here, we reported the function analysis of an AP2/ERF member, MhSHN1, from Malus hupehensis (Pamp.) Rehder. The MhSHN1 gene has a total of 1171 bp and consists of two exons of 81 and 531 bp, one intron of 559 bp. Phylogenetic analysis indicated MhSHN1 belongs to group V. The expression of MhSHN1 was highest in flower, then in seed and fruit, with low expression in root, leaves and stems. The MhSHN1 transcripts were barely affected by jasmonic acid (JA) and 1-aminocyclopropane- 1-carboxylic acid (ACC) within the first 48 h of treatment. Salicylic acid (SA) and abscisic acid (ABA) induce significantly the expression of MhSHN1. MhSHN1 mRNA levels were increased in response to mannitol and salt treatments. However, low temperature could not induce the expression of MhSHN1 gene. Overexpression of the MhSHN1 gene does not regulate seed germination but does positively regulate plant tolerance to salt and osmotic stresses at the stage of seed germination. These results showed the MhSHN1 gene play key role in resistance to mannitol and salt stresses in M. hupehensis. [ABSTRACT FROM AUTHOR]

Abstract Three novel strains namely, L1E11T, L1E4 and 228 were isolated as part of an ongoing study on 1-aminocyclopropane-1-carboxylate (ACC) deaminase expressing rhizobacteria from crops cultivated in saline affected coastal agro-ecosystems of Kerala, India. The novel strains were positive for many properties that are beneficial to plant growth including ACC deaminase (ACCd) activity that ranged from 1.87 ± 0.27 to 2.88 ± 0.71 μmol of α-ketobutyrate/hr/mg of total protein. Presence of other traits such as biofilm formation, siderophore production, phosphate solubilisation, utilisation of root derived compounds and ability to colonise host roots indicates its plant-associated life style. In complement, the genomic data reveals gene features for higher adaptation to plant-associated environments. In-planta assays showed that L1E11T can promote and protect pokkali rice plants from 200 mM NaCl stress. Phylogenetic, chemotaxonomic, phenotypic and genomic characterisation indicates that the novel strains belong to a novel genus and species of the order Oceanospirillales for which the names Pokkaliibacter gen. nov., and Pokkaliibacter plantistimulans sp. nov., are proposed with L1E11T (= DSM 28732T = MCC 2992T) as the type strain. Further, on the basis of low 16S rRNA sequence similarity, phylogenetic divergence, source of isolation and few differences in the phenotypic properties against its nearest taxon, a new family Balneatrichaceae fam. nov., is proposed to accommodate the two genera Balneatrix and Pokkaliibacter gen.nov. with Balneatrix as the type genus. An emended description of the genus Balneatrix is also presented. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the possible improvement of plant growth using the activity of the bacterial enzyme ACC (1-aminocyclopropane-1-carboxylate) deaminase (endophytes and rhizobacteria). The beneficial effect of ACC deaminase activity was tested on the plants growing under stress conditions (high concentrations of heavy metals: cadmium, lead, zinc in the soil). The bacteria were isolated from three plants species: Festuca rubra L., Agrostis capillaris L., Arabidopsis thaliana L. Heynh, acquired from the area contaminated with heavy metals. The strains with the highest ACC deaminase activity were used to prepare a bacterial consortium and inoculate the plants. It has been shown that inoculation of plants with ACC producing bacteria has a positive effect on their growth under stress conditions. The bacterial entophytes strains showed a higher activity of ACC deaminase, which resulted in a higher biomass growth of inoculated plants. The PGPB bacteria may limit the toxicity of harmful ions and thus the increase the adaptive properties of plants. Moreover, it was discovered that the bacteria mainly belonging to genus Bacillus and Pseudomonas had the highest ACC deaminase activity in the environment contaminated with multiple heavy metals. The use of selected microorganisms and plants will provide results in an increasing efficiency of phytoremediation. [ABSTRACT FROM AUTHOR]

Microbial activities are the indicators of soil strength. The present study explores the development of efficient predictive modeling systems for the estimation of specific soil microbial dynamics, phosphate solubilization (PS), bacterial population (BP), and 1-aminocyclopropane-1-carboxylate ACC-deaminase activity. More specifically, fuzzy c-means clustering (FCM)-FIS, Wang and Mendel’s (WM) fuzzy inference systems (FIS), adaptive neuro-fuzzy inference system (ANFIS), and subtractive clustering (SC) and have been implemented with the objective to achieve the best estimation accuracy of microbial dynamics. Experimental measurements were performed using controlled pot experiment using minimal salt media. Three experimental parameters, including temperature, pH, and incubation period have been used as inputs of FCM-FIS, SC-FIS, ANFIS, and WM-FIS methods. The SC-FIS method has the best estimation accuracy for the PS (R2 of 0.99) and BP (R2 of 0.94) than the rest three FIS methods. [ABSTRACT FROM AUTHOR]

Three new ternary iron(II) complexes, [(TpPh2)FeII(ACC)] (1), [(TpPh2)FeII(ACH)] (2), and [(TpPh2)FeII(ADP)] (3) [TpPh2 = hydrotris(3,5‐diphenylpyrazol‐1‐yl)borate, ACC‐H = 1‐aminocyclopropane‐1‐carboxylic acid, ACH‐H = 1‐aminocyclohexane‐1‐carboxylic acid, and ADP‐H = 2‐amino‐2,2‐diphenylacetic acid] were isolated and characterized. X‐ray crystal structures of 1 and 2 reveal that in both the complexes the TpPh2 ligand binds to the central iron atom in a facial mode, and the respective 1‐aminocarboxylate monoanion displays bidentate binding mode through one carboxylate oxygen and one amine nitrogen donor. Complex 1 represents a structural model of the enzyme‐substrate adduct of the enzyme, 1‐aminocyclopropane‐1‐carboxylic acid oxidase (ACCO). The iron(II) complexes react with O2 at ambient temperature to convert the metal coordinated coligands to the corresponding carbonyl compound but in low yields. The yields of the decarboxylated products, however, increase upon increasing the reaction temperature. Isotope labelling experiments and interception studies indicate that the reductive activation of O2 at the central iron atom concomitant with two‐electron oxidative decarboxylation of the coligand following a pathway very similar to that proposed for the iron(II)‐α‐hydroxy acid complexes of the TpPh2 ligand. [ABSTRACT FROM AUTHOR]

Abstract: The abscission of tomato leaves occurs in the petiole abscission zone, and its late stage includes two spatially divided processes: cell separation and programmed cell death (PCD). Both of these processes are regulated by ethylene. The last step in ethylene biosynthesis is conversion of 1‐aminocyclopropane‐1‐carboxylic acid to ethylene, which is catalysed by the enzyme 1‐aminocyclopropane‐1‐carboxylate oxidase (ACO); however, the location of ACO in the leaf petiole abscission zone is not known. The tomato gene LeLX encodes ribonuclease LX, which is a marker for PCD and is induced by ethylene during abscission, but its association with ACO has not been explored. In a tomato transgenic line 1‐7 with inhibited expression of LeLX showing delayed leaf abscission, the morphology and ultrastructure of the leaf petiole abscission zone was examined. In this zone of the cv.’VF36’ and of a transgenic line 1‐7, spatiotemporal differences in expression of LeACO1 and LeACO4 were analysed and ACO protein was detected immunohistochemically. In comparison to wild‐type plants, there were no obvious morphological and ultrastructural features in the abscission zone of plants of a transgenic line 1‐7 before and after abscission induction. LeACO1 expression was low before abscission induction, and increased 24 h after induction, although with no apparent spatial pattern. In contrast, LeACO4 was expressed before abscission induction, and its transcript level declined 24 h after induction on the distal side of the abscission zone fracture. In the LeLX‐inhibited transgenic line, there were no significant differences in LeACO1 and LeACO4 expression in the petiole abscission zone, in comparison to wild‐type plants. In addition, the ACO protein was immunolocalised to the vascular tissues that traverse the petiole abscission zone in plants of wild type and of a transgenic line 1‐7; and additionally in the plane of future abscission zone fracture of transgenic‐line plants. The results suggest temporal differential expression of the LeACO genes in tomato leaf petioles and vascular localisation of ACO1 protein. Additionally, the results indicate that expression of LeACO genes is not affected by suppression of the LeLX expression. [ABSTRACT FROM AUTHOR]

This study examines the association of auxin with ethylene and nitric oxide (NO) in regulating the magnesium (Mg) deficiency-induced root hair development in Arabidopsis thaliana. With Mg deficiency, both ethylene and NO promoted the elevation of root auxin levels in roots by inducing the expression of AUXIN-RESISTANT1 (AUX1), PINFORMED 1 (PIN1) and PIN2 transporters. In turn, auxin stimulated ethylene and NO production by activating the activities of 1-aminocyclopropane-1-carboxylate (ACC) oxidase (ACO), ACC synthase (ACS), nitrate reductase (NR) and NO synthase-like (NOS-L). These processes constituted an NO/ethylene-auxin feedback loop. Interestingly, however, the roles of ethylene and NO in regulating Mg deficiencyinduced root hair development required the action of auxin, but not vice versa. In summary, these results suggest that Mg deficiency induces a positive interaction between the accumulation of auxin and ethylene/NO in roots, with auxin acting downstream of ethylene and NO signals to regulate Mg deficiency-induced root hair morphogenesis. [ABSTRACT FROM AUTHOR]

Camelina sativa treated with plant growth-promoting bacteria (PGPB) producing 1-aminocyclopropane-1-carboxylate deaminase (acdS) or transgenic lines expressing acdS exhibit increased salinity tolerance. AcdS reduces the level of stress ethylene to below the point where it is inhibitory to plant growth. The study determined that several mechanisms appear to be responsible for the increased salinity tolerance and that the effect of acdS on gene expression patterns in C. sativa roots during salt stress is a function of how it is delivered. Growth in soil treated with the PGPB (Pseudomonas migulae 8R6) mostly affected ethylene- and abscisic acid-dependent signaling in a positive way, while expression of acdS in transgenic lines under the control of the broadly active CaMV 35S promoter or the root-specific rolD promoter affected auxin, jasmonic acid and brassinosteroid signaling and/biosynthesis. The expression of genes involved in minor carbohydrate metabolism were also up-regulated, mainly in roots of lines expressing acdS. Expression of acdS also affected the expression of genes involved in modulating the level of reactive oxygen species (ROS) to prevent cellular damage, while permitting ROS-dependent signal transduction. Though the root is not a photosynthetic tissue, acdS had a positive effect on the expression of genes involved in photosynthesis. [ABSTRACT FROM AUTHOR]

Heterosis is widely applied in agriculture; however, the underlying molecular mechanisms for superior performance are not well understood. Ethylene biosynthesis and signaling genes are shown to be down-regulated in Arabidopsis interspecific hybrids. Ethylene is a plant hormone that promotes fruit ripening and maturation but inhibits hypocotyl elongation. Here we report that application of exogenous ethylene could eliminate biomass vigor in Arabidopsis thaliana F1 hybrids, suggesting a negative role of ethylene in heterosis. Ethylene biosynthesis is mediated by the rate-limiting enzyme, 1-aminocyclopropane-1-carboxylate synthase (ACS). Downregulation of ACS genes led to the decrease of ethylene production, which was associated with the high-vigor F1 hybrids, but not with the low-vigor ones. At the mechanistic level, expression of ACS genes was down-regulated diurnally and indirectly by Circadian Clock Associated 1 (CCA1) during the day and directly by Phyotochrome-Interacting Factor 5 (PIF5) at night. Consistent with the negative role of ethylene in plant growth, biomass vigor was higher in the acs mutants than in wild-type plants, while increasing endogenous ethylene production in the hybridizing parents reduced growth vigor in the hybrids. Thus, integrating circadian rhythms and light signaling into ethylene production is another regulatory module of complex biological networks, leading to biomass heterosis in plants. [ABSTRACT FROM AUTHOR]

Endophytes are bacterial or fungal organisms associated with plants in an obligate or facultative manner. In order to maintain a stable symbiosis, many of the endophytes produce compounds that promote plant growth and help them adapt better to the environment. This study was conducted to explore the potential of jute bacterial endophytes for their growth promotion ability in direct and indirect ways. A total of 27 different bacterial species were identified from different varieties of a jute plant ( Corchorus olitorius ) and different parts of the plant (leaf, root, seed, and seedling) based on 16S rRNA gene sequence. Two of the isolates showed ACC deaminase activity with Staphylococcus pasteuri strain MBL_B3 and Ralstonia solanacearum strain MBL_B6 producing 18.1 and 8.08 μM mg −1  h −1 α-ketobutyrate respectively while eighteen had the ACC deaminase gene ( acdS ). Fourteen were positive for siderophore activity while Kocuria sp. strain MBL_B19 (133.36 μg/ml) and Bacillus sp. strain MBL_B17 (124.72 μg/ml) showed high IAA production ability. Seven bacterial strains were able to fix nitrogen with only one testing positive for nifH gene. Five isolates exhibited phosphorus utilization ability with Bacillus sp. strain MBL_B17 producing 218.47 μg P/ml. Three bacteria were able to inhibit the growth of a phytopathogen, Macrophomina phaseolina and among them Bacillus subtilis strain MBL_B4 was found to be the most effective, having 82% and 53% of relative inhibition ratio (RIR) and percent growth inhibition (PGI) values respectively. Nine bacteria were tested for their in vivo growth promotion ability and most of these isolates increased seed germination potential and vigour index significantly. Bacillus subtilis strain MBL_B13 showed 26.8% more vigour index than the control in which no bacterial inoculum was used. All inoculants were found to increase the dry weight of jute seedlings in comparison to the control plants and the most increase in fresh weight was found for Staphylococcus saprophyticus strain MBL_B9. Staphylococcus pasteuri strain MBL_B3 exhibited diverse in vitro growth promotion activity and significant growth promoting effect in in vivo pot experiments. These bacterial strains with plant growth enhancing abilities have the potential to be used as bioinoculants. [ABSTRACT FROM AUTHOR]

Lack of regulated expression and tissue specificity are the major drawbacks of plant and virus-derived constitutive promoters. A precise tissue or site-specific expression, facilitate regulated expression of proteins at the targeted time and site. Publically available microarray data on whitefly and aphid infested Arabidopsis thaliana L. was used to identify whitefly and aphid-inducible genes. The qRT-PCR further validated the inducible behaviour of these genes under artificial infestation. Promoter sequences of genes were retrieved from the Arabidopsis Information Resources database with their corresponding 5′UTR and cloned from the A. thaliana genome. Promoter reporter transcriptional fusions were developed with the beta-glucuronidase (GUS) gusA gene in a binary expression vector to validate the inducible behaviour of these promoters in eight independent transgenic Nicotiana tabaccum lines. Histochemical analysis of the reporter gene in T2 transgenic tobacco lines confirmed promoter driven expression at the sites of aphid and whitefly infestation. The qRT-PCR and GUS expression analysis of transgenic lines revealed that abscisic acid largely influenced the expression of both aphid and whitefly inducible promoters. Further, whitefly-specific promoter respond to salicylic acid and jasmonic acid (JA), whereas aphid-specific promoters to JA and 1-aminocyclopropane carboxylic acid. The response of promoters to phytohormones correlated to the presence of corresponding conserved cis-regulatory elements. [ABSTRACT FROM AUTHOR]

Ethylene and its precursor 1-aminocyclopropane-1-carboxylate (ACC) actively participate in plant developmental, defense and symbiotic programs. In this sense, ethylene and ACC play a central role in the regulation of bacterial colonization (rhizospheric, endophytic, and phyllospheric) by the modulation of plant immune responses and symbiotic programs, as well as by modulating several developmental processes, such as root elongation. Plant-associated bacterial communities impact plant growth and development, both negatively (pathogens) and positively (plantgrowth promoting and symbiotic bacteria). Some members of the plant-associated bacterial community possess the ability to modulate plant ACC and ethylene levels and, subsequently, modify plant defense responses, symbiotic programs and overall plant development. In this work, we review and discuss the role of ethylene and ACC in several aspects of plant-bacterial interactions. Understanding the impact of ethylene and ACC in both the plant host and its associated bacterial community is key to the development of new strategies aimed at increased plant growth and protection. [ABSTRACT FROM AUTHOR]

Drought is one of the major constraints limiting agricultural production worldwide and is expected to increase in the future. Limited water availability causes significant effects to plant growth and physiology. Plants have evolved different traits to mitigate the stress imposed by drought. The presence of plant growth-promoting rhizobacteria (PGPR) could play an important role in improving plant performances and productivity under drought. These beneficial microorganisms colonize the rhizosphere of plants and increase drought tolerance by lowering ethylene formation. In the present study, we demonstrate the potential to improve the growth of velvet bean under water deficit conditions of two different strains of PGPR with ACCd (1-Aminocyclopropane-1-Carboxylate deaminase) activity isolated from rainfed farming system. We compared uninoculated and inoculated plants with PGPR to assess: a) photosynthetic performance and biomass; b) ACC content and ethylene emission from leaves and roots; c) leaf isoprene emission. Our results provided evidence that under drought conditions inoculation with PGPR containing the ACCd enzyme could improve plant growth compared to untreated plants. Ethylene emission from roots and leaves of inoculated velvet bean plants was significantly lower than uninoculated plants. Moreover, isoprene emission increased with drought stress progression and was higher in inoculated plants compared to uninoculated counterparts. These findings clearly illustrate that selected PGPR strains isolated from rainfed areas could be highly effective in promoting plant growth under drought conditions by decreasing ACC and ethylene levels in plants. [ABSTRACT FROM AUTHOR]

Ethylene influences many aspects of plant growth and development. The biosynthesis of ethylene is highly regulated by a variety of internal and external cues. A key target of this regulation is 1-aminocyclopropane-1-carboxylic acid ( ACC) synthases ( ACS), generally the rate-limiting step in ethylene biosynthesis, which is regulated both transcriptionally and post-transcriptionally. Prior studies have demonstrated that cytokinin and brassinosteroid ( BR) act as regulatory inputs to elevate ethylene biosynthesis by increasing the stability of ACS proteins. Here, we demonstrate that several additional phytohormones also regulate ACS protein turnover. Abscisic acid, auxin, gibberellic acid, methyl jasmonic acid, and salicylic acid differentially regulate the stability of ACS proteins, with distinct effects on various isoforms. In addition, we demonstrate that heterodimerization influences the stability of ACS proteins. Heterodimerization between ACS isoforms from distinct subclades results in increased stability of the shorter-lived partner. Together, our study provides a comprehensive understanding of the roles of various phytohormones on ACS protein stability, which brings new insights into crosstalk between ethylene and other phytohormones, and a novel regulatory mechanism that controls ACS protein stability through a heterodimerization of ACS isoforms. [ABSTRACT FROM AUTHOR]

Aims: The present study was planned to investigate the diversity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing bacteria from the rhizosphere of wheat plants and subsequent evaluation of selected PGPR on growth enhancement of wheat seedlings under drought and saline conditions. Methods: ACC deaminase producing plant growth promoting rhizobacteria (PGPR) were isolated from the rhizosphere of wheat and identified using 16S rRNA gene sequence analysis. Isolates were evaluated for various direct and indirect plant growth promoting (PGP) traits. Plant inoculation experiment was conducted using isolates IG 19 and IG 22 in wheat to assess their plant growth promotion potential under salinity and drought stress. Results: Thirty-eight ACC deaminase producing PGPR were isolated which belonged to 12 distinct genera and falling into four phyla γ-proteobacteria, β-proteobacteria, Flavobacteria and Firmicutes. Klebsiella sp. was the most abundant genera and followed by Enterobacter sp. The isolates exhibited ACC deaminase activities ranging from 0.106-0.980 μM α- ketobutyrate μg protein h. The isolates showed multiple PGP traits such as IAA production, phosphate, zinc, potassium solubilization and siderophore production. Enterobacter cloacae (IG 19) and Citrobacter sp. (IG 22) inoculated wheat seedlings showed notable increases in fresh and dry biomass under non-stress as well as under stressed condition. Conclusion: To the best of our knowledge this is the first report of presence of ACC deaminase activity and other PGP traits from the genus Citrobacter and Empedobacter. Our finding revealed that the γ-proteobacteria group dominated the wheat rhizosphere. Plant inoculation with PGPR could be a sustainable approach to alleviate abiotic stresses in wheat plants. These native PGPR isolates could be used as potential biofertilizers for sustainable agriculture. [ABSTRACT FROM AUTHOR]

Flavescence dorée is an epidemic yellows disease of grapevine, caused by a phytoplasma (FDP), for which there is currently no cure. We assessed whether the endophytePseudomonas migulae8R6, able to synthesize 1-aminocyclopropane-1-carboxylate (ACC) deaminase, can limit the phytoplasma-induced damages in periwinkle, a model plant hosting FDP. Plant protection induced by 8R6 and its mutant, impaired in ACC deaminase synthesis, was compared. Fifteen plants per treatment were used; FD infection was transmitted by grafting. Evaluation of symptoms was performed every 4 days for 40 days. The presence and the amount of FDP were assessed by nested PCR and qPCR, respectively. Images of phytoplasma inside the infected plants were obtained by transmission electron microscopy. The strain 8R6 significantly reduced the number of symptomatic plants (53% vs 93%). While the density of FDP inside the leaves was unaffected by the bacterial strains, the FDP titre was under the quantification threshold in 38% of the plants inoculated with strain 8R6. Microscopical observations showed damaged FDP cells in plants inoculated with strain 8R6. The ACC deaminase activity of the endophytic bacteriaP. migulae8R6 helps the plant to regulate the level of the stress-related hormone ethylene, leading to significantly improved resistance to phytoplasma infection. [ABSTRACT FROM PUBLISHER]

Background: Ethylene plays an important role in the regulation of floral organ development in soybean, and 1-aminocyclopropane-1-carboxylate synthase (ACS) is a rate-limiting enzyme for ethylene biosynthesis. However, whether ACS also regulates floral organ differentiation in soybean remains unknown. To address this, we constructed an RNAi vector to inhibit ACS expression in cotyledonary nodes. Linear DNA cassettes of RNAi-ACS obtained by PCR were used to transform soybean cotyledonary nodes. Results: In total, 131 of 139 transiently transformed plants acquired herbicide resistance and displayed GUS activities in the new buds. In comparison to untransformed seedling controls, a greater number of flower buds were differentiated at the cotyledonary node; GM-ACS1 mRNA expression levels and ethylene emission in the transformed buds were reduced. Conclusion: These results indicate that the cotyledonary node transient transformation system may be suitable for stable transformation and that the inhibition of ACS expression may be an effective strategy for promoting floral organ differentiation in soybean. [ABSTRACT FROM AUTHOR]

Phytostabilisation can benefit from phytostimulatory rhizobacteria. Forty-three bacterial strains were isolated from the roots of the metallicolous legume Anthyllis vulneraria ssp. carpatica grown in a highly contaminated mine tailing (total Cd, Pb and Zn were up to 1200; 34,000; and 170,000 mg kg, respectively). We aimed at evaluating their phytostimulatory effects on the development of leguminous metallophytes. Strains were screened for fluorescent siderophores and auxin synthesis, inorganic P solubilisation and 1-amino-cyclopropane-1-carboxylate deaminase (ACCd) activity to define a subset of 11 strains that were inoculated on the leguminous metallophytes A. vulneraria and Lotus corniculatus grown in diluted mine spoil (Zn 34,653; Pb 6842; and Cd 242, all in mg kg). All strains were affiliated to Pseudomonas spp. (except two), synthetised auxins and siderophores and solubilised P (except three), and seven of them were ACCd positive. The inoculation effects (shoot-root-nodule biomass, chlorophyll content) depended on legume species and bacterial strain genotype. Phytostimulation scores were unrelated to siderophore/auxin synthesis and P solubilisation rates. Inoculations of the strain nos. 17-43 triggered a 1.2-fold significant increase in the chlorophyll content of A. vulneraria. Chlorophyll content and root biomass of L. corniculatus were significantly increased following the inoculations of the strain nos. 17-22 (1.5-1.4-fold, respectively). The strongest positive effects were related to increases in the nodule biomass of L. corniculatus in the presence of three ACCd-positive strains (1.8-fold), one of which was the highest auxin producer. These data suggest to focus on interactions between ACCd activity and auxin synthesis to enhance nodulation of metallicolous legumes. [ABSTRACT FROM AUTHOR]

Pollination initiates a suite of postpollination developmental events in orchid flowers. Ethylene plays a key role in coordinating these developmental changes. We examined the temporal-spatial patterns of expression of genes encoding 1-aminocyclopropane 1-carboxylate acid (ACC) synthase and ACC oxidase following pollination and associated hormonal treatments using quantitative procedures. We present the first in situ hybridization analysis of ACC synthase and an earlier time course of ACC oxidase gene expression. In immature ovaries, critical morphological changes involving cell differentiation and growth were affected by pollination and various hormone and inhibitor treatments. Patterns of ACC synthase and ACC oxidase mRNA accumulation were determined by RNA blot hybridization analysis. Gene expression analysis using real-time quantitative polymerase chain reaction indicated that the unpollinated ovary had very low levels of ACC oxidase expression at 6 h and that pollination caused near-maximal levels in this organ by 12 h. Quantitative mRNA analysis showed that auxin could mimic pollination by inducing a similar pattern of organ-specific expression, but earlier and to higher levels. Ethylene had the most dramatic effect by inducing gene activity to its highest levels at all time points and in all floral organs. The early induction in situ hybridization analyses contribute new findings that ACC synthase and ACC oxidase transcripts were localized sequentially in epidermal, phloem, and parenchyma cells of the stigma and that by 8-12 h postpollination, saturation had occurred throughout the stigma. Finally, phylogenetic analysis of orchid ACC synthase proteins leads to the conclusion that at least a subgroup of the angiosperm ACC synthase gene family is induced by auxin but may not be posttranscriptionally regulated, indicating regulatory sequence but not functional divergence of orchid genes with other seed plant ACC synthase proteins. [ABSTRACT FROM AUTHOR]

Camelina sativa (camelina) is an oilseed crop touted for use on marginal lands; however, it is no more tolerant of soil salinity than traditional crops, such as canola. Plant growth-promoting bacteria (PGPB) that produce 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) facilitate plant growth in the presence of abiotic stresses by reducing stress ethylene. Rhizospheric and endophytic PGPB and the corresponding acdS- mutants of the latter were examined for their ability to enhance tolerance to salt in camelina. Stimulation of growth and tolerance to salt was correlated with ACC deaminase production. Inoculation of soil with wild-type PGPB led to increased shoot length in the absence of salt, and increased seed production by approximately 30-50% under moderately saline conditions. The effect of ACC deaminase was further examined in transgenic camelina expressing a bacterial gene encoding ACC deaminase (acdS) under the regulation of the CaMV 35S promoter or the root-specific rolD promoter . Lines expressing acdS, in particular those using the rolD promoter, showed less decline in root length and weight, increased seed production, better seed quality and higher levels of seed oil production under salt stress. This study clearly demonstrates the potential benefit of using either PGPB that produce ACC deaminase or transgenic plants expressing the acdS gene under the control of a root-specific promoter to facilitate plant growth, seed production and seed quality on land that is not normally suitable for the majority of crops due to high salt content. [ABSTRACT FROM AUTHOR]

The search for efficient and selective routes for the synthesis of chiral aminocyclopropane derivatives is of great interest and importance as these structures are important components of biologically active natural products and pharmaceuticals. We herein report the enantioselective intermolecular hydroamination of substituted cyclopropenes with various amines catalyzed by chiral half-sandwich rare-earth-metal complexes. This method constitutes a 100 % atom-efficient route for the synthesis of a variety of chiral α-aminocyclopropane derivatives in high yields (up to 96 %) and excellent stereoselectivity (up to >20:1 d.r. and 99 % ee) under mild reaction conditions (25 °C). [ABSTRACT FROM AUTHOR]

A typical plant response to any biotic or abiotic stress, including cadmium (Cd), involves increased ethylene synthesis, which causes senescence of the affected plant part. Stressed plants can experience reduced ethylene and improved growth if they are inoculated with bacteria that have the enzyme ACC deaminase, which metabolizes the ethylene precursor ACC (1-aminocyclopropane-1-carboxylate). We investigated whether one such bacterium, Pseudomonas fluorescens UW4, reduces the production of ethylene and improves the growth of lettuce ( Lactuca sativa) sown in Cd-contaminated potting material (PRO-MIX® BX). Plants were inoculated with the wild-type P. fluorescens UW4 or a mutant strain that cannot produce ACC deaminase. Cadmium-treated plants contained up to 50 times more Cd than did control plants. In noninoculated plants, Cd induced a 5-fold increase in ethylene concentration. The wild-type bacterium prevented Cd-induced reductions in root biomass but there was no relationship between Cd treatment and ethylene production in inoculated plants. In contrast, when the concentration of ethylene was plotted against the extent of bacterial colonization of the roots, increased colonization with wild-type P. fluorescens UW4 was associated with 20% less ethylene production. Ours is the first study to show that the protective effect of this bacterium is proportional to the quantity of bacteria on the root surface. [ABSTRACT FROM AUTHOR]

The expression and accumulation of members of the 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) and ACC oxidase (ACO) gene families was examined in white clover roots grown in either Pi (phosphate) sufficient or Pi-deprived defined media. The accumulation of one ACO isoform, TR-ACO1, was positively influenced after only 1 h of exposure to low Pi, and this was maintained over a 7-day time-course. Up-regulation of TR-ACS1, TR-ACS2 and TR-ACS3 transcript abundance was also observed within 1 h of exposure to low Pi in different tissue regions of the roots, followed by a second increase in abundance of TR-ACS2 after 5-7 days of exposure. An increase in transcript abundance of TR-ACO1 and TR-ACO3, but not TR-ACO2, was observed after 1 h of exposure to low Pi, with a second increase in TR-ACO1 transcripts occurring after 2-5 days. These initial increases of the TR-ACS and TR-ACO transcript abundance occurred before the induction of Trifolium repens PHOSPHATE TRANSPORTER 1 (TR-PT1), and the addition of sodium phosphite did not up-regulate TR-ACS1 expression over 24 h. In situ hybridization revealed some overlap of TR-ACO mRNA accumulation, with TR-ACO1 and TR-ACO2 in the root tip regions, and TR-ACO1 and TR-ACO3 mRNA predominantly in the lateral root primordia. TR-ACO1p-driven GFP expression showed that activation of the TR-ACO1 promoter was initiated within 24 h of exposure to low Pi (as determined by GFP protein accumulation). These results suggest that the regulation of ethylene biosynthesis in white clover roots is biphasic in response to low Pi supply. [ABSTRACT FROM AUTHOR]

Aims: The plant-beneficial bacterium Pseudomonas fluorescens F113 harbours an acdS gene, which enables deamination of 1-aminocyclopropane-1-carboxylate. The impact of abiotic and biotic factors on the expression of this gene was assessed, as well as the plant-beneficial properties of F113 under different soil moistures. Methods: An acdS- egfp biosensor was constructed in F113, validated in vitro and used to analyse, by microscopy, its expression on roots of Zea mays comparatively to Beta vulgaris. An acdS mutant was constructed and compared with the wild-type to characterize plant-beneficial effects of F113 on maize lines EP1 and FV2, under well-watered and water deficit conditions. Results: Different patterns of root colonization and acdS expression were observed according to plant genotype. acdS rhizoplane expression was higher on Beta vulgaris, and on maize line FV2 and hybrid PR37Y15 than on maize line EP1 and teosinte. Strain F113 but not its acdS mutant promoted root growth of EP1 under well-watered conditions and germination of FV2 under water deficit conditions. Conclusions: Maize lines differed in their ability to induce acdS expression and to respond to P. fluorescens F113. The maize line leading to higher acdS expression, FV2, was the one benefiting from inoculation under water deficit. [ABSTRACT FROM AUTHOR]

Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests stamen development. Five sex-determination genes have been identified, including four encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase that catalyzes the rate-limiting step in ethylene biosynthesis, and a transcription factor gene CmWIP1 that corresponds to the Mendelian locus gynoecious in melon and is a negative regulator of femaleness. ACC oxidase (ACO) converts ACC into ethylene; however, it remains elusive which ACO gene in the cucumber genome is critical for sex determination and how CmWIP1 represses development of female flowers. In this study, we discovered that mutation in an ACO gene, CsACO2 , confers androecy in cucumber that bears only male flowers. The mutation disrupts the enzymatic activity of CsACO2, resulting in 50% less ethylene emission from shoot tips. CsACO2 was expressed in the carpel primordia and its expression overlapped with that of CsACS11 in female flowers at key stages for sex determination, presumably providing sufficient ethylene required for proper CsACS2 expression. CmACO3 , the ortholog of CsACO2 , showed a similar expression pattern in the carpel region, suggesting a conserved function of CsACO2/CmACO3. We demonstrated that CsWIP1, the ortholog of CmWIP1, could directly bind the promoter of CsACO2 and repress its expression. Taken together, we propose a presumably conserved regulatory module consisting of WIP1 transcription factor and ACO controls unisexual flower development in cucumber and melon. [ABSTRACT FROM AUTHOR]

Salt stress reduces plant growth and is now becoming one of the most important factors restricting agricultural productivity. Inoculation of plant growth-promoting rhizobacteria (PGPR) has been shown to confer plant tolerance against abiotic stress, but the detailed mechanisms of how this occurs remain unclear. In this study, hydroponic experiments indicated that the PGPR strain Bacillus amyloliquefaciens SQR9 could help maize plants tolerate salt stress. After exposure to salt stress for 20 days, SQR9 significantly promoted the growth of maize seedlings and enhanced the chlorophyll content compared with the control. Additional analysis showed that the involved mechanisms could be the enhanced total soluble sugar content for decreasing cell destruction, improved peroxidase/catalase activity and glutathione content for scavenging reactive oxygen species, and reduced Na+ levels in the plant to decrease Na+ toxicity. These physiological appearances were further confirmed by the upregulation of RBCS, RBCL, H+-PPase, HKT1, NHX1, NHX2 and NHX3, as well as downregulation of NCED expression, as determined by quantitative reverse transcription-polymerase chain reaction. However, SQR9 counteracted the increase of abscisic acid in response to salt stress. In summary, these results show that SQR9 confers plant salt tolerance by protecting the plant cells and managing Na+ homeostasis. Hence, it can be used in salt stress prone areas, thereby promoting agricultural production. [ABSTRACT FROM AUTHOR]

Soybean is stress-sensitive crop that exhibits markedly reduced growth under flooding and drought conditions. Three S-adenosylmethionine synthetases (SAMs) proteins were identified as flooding and drought responsive proteins in soybean using a proteomic technique. To better understand the role of these SAMs proteins in soybean under flooding and drought stresses, temporal, organ, and stress specificities were examined at mRNA and enzyme activity levels. The activity of SAMs decreased in response to the flooding, however, it was not significantly changed by NaCl, cold, gibberellic acid, and calcium in soybean roots. The activity of SAMs was induced in roots and hypocotyls under drought. The mRNA expression of the S- adenosylmethionine synthetase ( SAMs) family was down-regulated in root tips and roots under the flooding and the drought, and SAMs 1 and SAMs 2 were down-regulated in roots under both stresses. A gene 1-aminocyclopropane-1-carboxylate synthase was up-regulated in root tips, roots, and hypocotyls under drought, however, it was not changed in root tips and roots under the flooding. In addition, 1-aminocyclopropane-1-carboxylate oxidase was induced in root tips under flooding and drought. These results suggest that SAMs was involved in the response to the flooding and drought and it might affect ethylene biosynthesis in soybean. [ABSTRACT FROM AUTHOR]

The higher content of salt in soil is the key constraint to crop productivity. Induction of stress ethylene production from 1-aminocyclopropane-1-carboxylate (ACC) in the plant system is one of the consequences of salt stress responsible for toxicity to the plant. Several transgenic plants have been developed by expressing the ACC deaminase bacterial gene as a stress management strategy which apart from being a costly proposition lacks public acceptability. Our main objective was to investigate if a plant inoculated with ACC-deaminase-producing bacterial endophyte will effectively mitigate salt-induced damage and act as an alternative to transgenics. An ACC deaminase-producing salt-tolerant endophyte SMR20 ( Brachybacterium paraconglomeratum) was isolated from the roots of Chlorophytum borivilianum, a medicinal plant sensitive to salt stress. Initially we tested ACC-deaminase-producing SMR20 for amelioration of salt stress-induced damage at three different concentrations of salt, that is, 0, 75, 100 and 150 mM NaCl. 150 mM salt stress was selected for further study because wider differences between inoculated and uninoculated plants were noticed under this concentration of NaCl stress. Inoculated with SMR20 successfully protected C. borivilianum from salt stress-induced crop losses. SMR20 significantly alleviated the negative impact of salinity by potential deamination of ACC (precursor for ethylene generation) in the host Chlorophytum roots leading to decreased production of stress ethylene, delayed chlorosis and senescence that resulted in improved yield of plants. Apart from reducing stress ethylene, the presence of the endophyte also affected other phytohormone quantities like indole-3-acetic acid and abscisic acid in plants. It also altered the amount of total leaf pigments and biochemical compounds like proline, malondialdehyde and enhanced foliar nutrient uptake. Due to these outcomes, it appears that an ACC-deaminase-producing endophyte can enhance crop tolerance against salinity stress and can be an important area to explore. [ABSTRACT FROM AUTHOR]

Key message: Two ACC synthase-like (ACL) proteins in the moss Physcomitrella patens have no ACS activity, and PpACL1 functions as an l -cystine/ l -cysteine C-S lyase. Abstract: The ethylene biosynthetic pathway has been well characterized in higher plants, and homologs of a key enzyme in this pathway, ACS, have been reported in several algae and mosses, including Physcomitrella patens. However, the function of the ACS homologs in P. patens has not been investigated. In this research, we cloned two putative ACS genes from the P. patens genome, namely PpACS- Like 1 and 2, and investigated whether their encoded proteins had in vitro and in vivo ACS activity. In vitro biochemical assays using purified PpACL1 and PpACL2 showed that neither protein had ACS activity. Subsequently, we generated transgenic Arabidopsis lines expressing 35S:PpACL1 and 35S:PpACL2, and found that the transgenic etiolated seedlings that overexpressed either of these proteins lacked the constitutive triple response phenotype and did not emit excess levels of ethylene, indicating that neither of the PpACS-Like proteins had in vivo ACS activity. Furthermore, we found that PpACL1 functions as a C-S lyase that uses l-cystine and l-cysteine as substrates, rather than as an aminotransferase. Together, these results indicated that PpACL1 and PpACL2 are not true ACS genes as those found in higher plants. [ABSTRACT FROM AUTHOR]

‘Saijo’ Japanese persimmon ( Diospyros kaki Thumb.) is one of the most popular and commercially important fruit cultivars in Japan. In 2000, origin-unknown ‘Saijo’-like cultivar was found at the Shimane farm and named as ‘M-3’. Although it has similar morphological and physiological characteristics with ‘Saijo’ cultivars, its fruit size is apparently bigger than ‘Saijo’ making them an attractive candidate as novel valuable fruit for farm household. In this study, to elucidate the genealogical relationship of ‘M-3’, we conducted the restriction fragment length polymorphism (RFLP) analysis using genomic DNA of Japanese persimmon (‘Saijo’ lines, pollinizers, and other cultivars that bloom a male flower) detected by cDNA probes involved in genes coding persimmon fruit ripening: 1-aminocyclopropane-1-carboxylate synthase 1 ( ACCS-1 ), ACC oxidase 1 ( ACCO-1 ), and polygalacturonase ( PG-9 ). We demonstrated that ‘M-3’ line shares several RFLPs specific to ‘Saijo’ lines, pollinizers, and other cultivars. We found that morphological features of fruit and leaf in ‘M-3’ resembled that of ‘Saijo’ and pollinizer lines. These results strongly suggest that ‘M-3’ is likely the seedlings crossbred by ‘Saijo’ and pollinizer cultivars. Our findings provide first insight of genealogical origins of valuable newly identified persimmon cultivar and an important suggestion to establish a new valuable ‘Saijo’ cultivar by cross breeding with pollinizer lines. [ABSTRACT FROM AUTHOR]

Background: Oligogalacturonic acids (OGs) are oligomers of alpha-1,4-linked galacturonosyl residues that are released from cell walls by the hydrolysis of polygalacturonic acids upon fruit ripening and under abiotic/biotic stress. OGs may induce ethylene production and fruit ripening, however, the mechanism(s) behind these processes is unknown. Results: Tomato cultivar 'Ailsa Craig' (AC) and mutant Neverripe, ripening inhibitor, non-ripening, and colorless non-ripening fruits were treated with OGs at different stages. Only AC fruits at mature green stage 1 showed an advanced ripening phenomenon, although transient ethylene production was detected in all of the tomato fruits. Ethylene synthesis genes LeACS2 and LeACO1 were rapidly up-regulated, and the phosphorylated LeACS2 protein was detected after OGs treatment. Protein kinase/phosphatase inhibitors significantly affected the ripening process induced by the OGs. As a potential receptor of OGs, LeWAKL2 was also up-regulated in their presence. Conclusions: We demonstrated that OGs promoted tomato fruit ripening by inducing ethylene synthesis through the regulation of LeACS2 at transcriptional and post-translational levels. [ABSTRACT FROM AUTHOR]

1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) is a rate-limiting enzyme in the biosynthesis of ethylene which regulates many aspects of the plant development and responses to biotic and abiotic stresses. In this study, a full-length cDNA of ACC synthase, OnACS2, was cloned from the senescing flower of Oncidium Gower Ramsey by RACE. The full-length cDNA of OnACS2 (GenBank accession no. JQ822087 ) was 1557 bp in length with an open reading frame (ORF) of 1308 bp encoding for a protein of 435 amino acid residues. The predicted OnACS2 protein had a molecular mass of 49.1 kDa with pI value of 7.51. Phylogenetic analysis indicated its evolutionary relationships with corresponding orthologous sequences in orchids, Hosta ventricosa and monocots. Real-time PCR assay demonstrated that OnACS2 was constitutively expressed in all tested organs with the highest transcript level in the gynandria. Differential expression pattern of OnACS2 gene correlated to the ethylene production and the subsequent occurrence of senescent symptoms in flower suggested that OnACS2 probably played an important role in the initiation of flower senescence. [ABSTRACT FROM AUTHOR]

This study was conducted during 2011 and 2012 to evaluate the effect of 1-aminocyclopropane-1-carboxylate (ACC) deaminase-containing, N2-fixing and P-solubilizing bacteria on the yield and morpho-physiological parameters of strawberry. A total of 8 applications at the trial set, with four water regimes were randomly distributed into the pots. The diminishing water supply caused a gradual decrease in the plant growth, chlorophyll content and berry yield, accompanied by increasing activities of drought stress markers such as total phenolics content (TPC), trolox equivalent antioxidant capacity (TEAC), malondialdehyde (MDA) content, hydrogen peroxide (H2O2), glutathione reductase (GR), glutathione S-transferase (GST), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and ascorbate peroxidase (APX) in the leaves of strawberry. The multi-trait bacteria also increased plant growth and yield as well as TPC, TEAC, antioxidant enzymes (GR, GST, CAT, POD, SOD and APX) activity, phytohormone (GA, SA and IAA) and the contents of N, P, K, Ca, Fe, Mn, Zn and Cu, but decreased MDA and H2O2 contents which may contribute in part to activation of physiological and biochemical processes involved in the alleviation of the effect of drought stress. [ABSTRACT FROM AUTHOR]

The aim of the present study was to genetically modify plantlets of the Chinese yali pear to reduce their expression of ripening-associated 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) and therefore increase the shelf-life of the fruit. Primers were designed with selectivity for the conserved regions of published ACO gene sequences, and yali complementary DNA (cDNA) cloning was performed by reverse transcription quantitative polymerase chain reaction (PCR). The obtained cDNA fragment contained 831 base pairs, encoding 276 amino acid residues, and shared no less than 94% nucleotide sequence identity with other published ACO genes. The cDNA fragment was inversely inserted into a pBI121 expression vector, between the cauliflower mosaic virus 35S promoter and the nopaline synthase terminator, in order to construct the anti-sense expression vector of the ACO gene; it was transfected into cultured yali plants using Agrobacterium LBA4404. Four independent transgenic lines of pear plantlets were obtained and validated by PCR analysis. A Southern blot assay revealed that there were three transgenic lines containing a single copy of exogenous gene and one line with double copies. The present study provided germplasm resources for the cultivation of novel storage varieties of pears, therefore providing a reference for further applications of anti-sense RNA technology in the genetic improvement of pears and other fruit. [ABSTRACT FROM AUTHOR]

The study evaluates the effect of rhizobacteria having 1-aminocyclopropane-1-carboxylate deaminase (ACCd) on the development of wheat seedlings. This enzyme has been proposed to play a key role in microbe-plant association. Three fluorescent pseudomonads containing this deaminase were selected from 70 strains of pseudomonads isolated from rhizosphere of wheat ( Triticum aestivum L.) and rape ( Brassica napus L.). These bacteria, varied significantly in the ability to both biosynthesize auxins and hydrolyze ACC. Among them, Pseudomonas brassicacearum subsp. brassicacearum strain RZ310 presented the highest activities of ACC deaminase during 96 h of growth in liquid Dworkin and Foster (DF) salt medium. Additionally, this rape rhizosphere strain did not produce indoles. Two other isolates, Pseudomonas sp. PO283 and Pseudomonas sp. PO366, secreted auxins only in the presence of their precursor. Phylogenetic analysis of the 16S rRNA gene and four other protein-encoding genes indicated that these wheat rhizosphere isolates belonged to the fluorescent Pseudomonas group. Moreover, the effects of these strains on wheat seedling growth under in vitro conditions were markedly dependent on both their cell suspensions used to grain inoculation and nutrient conditions. Strains tested had beneficial influence on wheat seedlings mainly at low cell densities. In addition, access to nutrients markedly changed bacteria action on cereal growth. Their presence generally favored the positive effects of pseudomonads on length and the estimated biomasses of wheat coleoptiles. Despite these general rules, impacts of each isolate on the growth parameters of cereal seedlings were unique. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) plays a fundamental role in plant defense-signaling network. Recently, we have established the involvement of GSH with ethylene (ET) to combat environmental stress. However, the mechanism of GSH-ET interplay still remains unexplored. Here, we demonstrate that GSH induces ET biosynthesis by modulating the transcriptional and posttranscriptional regulations of its key enzymes, 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO). Transgenic Arabidopsis (Arabidopsis thaliana) plants with enhanced GSH content (AtECS) exhibited remarkable up-regulation of ACS2, ACS6, and ACO1 at transcript as well as protein levels, while they were down-regulated in the GSH-depleted phytoalexin deficient2-1 (pad2-1) mutant. We further observed that GSH induced ACS2 and ACS6 transcription in a WRKY33-dependent manner, while ACO1 transcription remained unaffected. On the other hand, the messenger RNA stability for ACO1 was found to be increased by GSH, which explains our above observations. In addition, we also identified the ACO1 protein to be a subject for S-glutathionylation, which is consistent with our in silico data. However, S-glutathionylation of ACS2 and ACS6 proteins was not detected. Further, the AtECS plants exhibited resistance to necrotrophic infection and salt stress, while the pad2-1 mutant was sensitive. Exogenously applied GSH could improve stress tolerance in wild-type plants but not in the ET-signaling mutant ethylene insensitive2-1, indicating that GSH-mediated resistance to these stresses occurs via an ET-mediated pathway. Together, our investigation reveals a dual-level regulation of ET biosynthesis by GSH during stress. [ABSTRACT FROM AUTHOR]

Petroleum is potentially toxic to living organisms, and there are worldwide efforts to develop methods for bioremediation of petroleum-contaminated soils. Phytoremediation is an effective method to reduce the concentration of petroleum in soils, and plant growth-promoting rhizobacteria (PGPR) play an important role in the phytoremediation. Two PGPR, Pseudomonas aeruginosa SLC-2 and Serratia marcescens BC-3, were isolated from the rhizophere of Echinochloa grown in petroleum-contaminated soil. These isolates showed capacities for 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole acetic acid production, siderophore synthesis, and the degradation of petroleum. The ACC deaminase activity of SLC-2 and BC-3 was 2.52 ± 0.03 μmol α-KA (mg Pr·h) and 38.52 ± 0.37 μmol α-KA (mg Pr·h), respectively. On the other hand, when the concentration of l-Trp increased, the IAA synthesis of BC-3 also increased, while the synthesis of SLC-2 did not change significantly. The ability of synthesized siderophore of SLC-2 was much higher than that of BC-3. The petroleum degradations of SLC-2 and BC-3 increased 4.78 and 7.36 %, respectively. The pot experiment of oat was performed to evaluate the plant growth-promoting abilities of SLC-2 and BC-3. Compared with non-inoculated controls, the height and fresh weight of stems increased (23.64 and 42.57) % and (16.98 and 28.3) %, respectively, whereas the length and fresh weight of roots also increased (10.34 and 20.84) and (24.13 and 43.11) %, respectively, when inoculated with SLC-2 and BC-3. The results indicated that P. aeruginosa SLC-2 and S. marcescens BC-3 can serve as promising microbes for increasing plant growth in petroleum-contaminated soil to improve the phytoremediation efficiency. [ABSTRACT FROM AUTHOR]

As a continuity of the [Cu II (AIB)(bpy)(H 2 O)](ClO 4 ) 2 -containing ( 1 ) ACCO (1-aminocyclopropane-1-carboxylate oxidase) model, two new copper(II)–amino acid complexes [Cu II 2 (AIB) 2 (PBI) 2 (CH 3 OH)(ClO 4 )]ClO 4 ( 2 ) and [Cu II 2 (AIB) 2 (PBT) 2 (H 2 O)](ClO 4 ) 2 ·CH 3 OH ( 3 ) with a modified hetero-bidentate ligands (PBT = 2-pyridin-2-yl-benzothiazole and PBI = 2-pyridin-2-yl-1 H -benzoimidazole) have been synthesized, characterized by various techniques including IR, UV–Vis, electrochemical and X-ray measurements, and investigated their reactivity toward H 2 O 2 with respect to the redox behavior compare to 1 . [ABSTRACT FROM AUTHOR]

High ethylene production usually slackens spikelets development in compact panicled rice ( Oryza sativa L.) cultivars. 1-Methylcyclopropene (1-MCP) is a potent inhibitor of ethylene action that has been shown to prevent ethylene-induced effects in fruits. However, effects of 1-MCP on spikelets development in rice cultivars differing in panicle types are unclear. This study explored whether 1-MCP is involved in regulating rice flag leaf function, and superior and inferior spikelets development. Four rice cultivars were field grown in 2012 and 2013, including two lax-panicled cultivars, Liangyoupeijiu (LYP9) and Guodao 6 (GD6), and two compact-panicled cultivars, Yongyou 9 (YY9) and Yongyou 12 (YY12). Results showed that 1-MCP played a positive role in regulating photosynthetic rate of rice flag leaf. Application of 1-MCP was more effective on enhancing grain filling rate of LYP9, GD6, and YY9. 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) activity and ethylene production of inferior spikelets were more sensitive to the regulation of 1-MCP comparing to that in superior spikelets. Compared to other cultivars, ACS activity and ethylene production in inferior spikelets of LYP9 with 1-MCP treatment were significantly lower than that in control (CK). Effect of 1-MCP on starch content in superior and inferior spikelets varied with rice cultivars, but application of 1-MCP significantly enhanced starch content of inferior spikelets for LYP9. To compare with CK, application of 1-MCP greatly increased grain yield, spikelet fertility, and harvest index for LYP9, GD6, and YY9, especially for LYP9. Results indicate that 1-MCP favorably regulated flag leaf photosynthesis and inferior spikelets development in rice cultivars used in this trial, and LYP9 showed the best performances after application of 1-MCP. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to isolate plant growth-promoting rhizobacteria (PGPR) that exhibit heavy metal resistance to examine their influence on Cd uptake and soil microbial community structure during phytoremediation. Materials and methods: Heavy metal-tolerant PGPR were isolated from the roots of possible hyperaccumulators using plates with 1-aminocyclopropane-1-carboxylate (ACC) as sole nitrogen source. Minimal inhibitory concentrations (MICs) of each isolate were determined by the plate dilution method. The impacts of isolated PGPR on the growth and Cd accumulation of Sedium plumbizincicola were conducted in a pot experiment. In addition, the effect of PGPR inoculation on the microbial community during phytoextraction by S. plumbizincicola was studied by 454 pyrosequencing. Results and discussion: A total of nine Cd-resistant strains were isolated from the roots of Cd accumulators, and their plant growth-promoting activities were characterized. Isolates were able to produce indole-3-acetic acid (IAA) (28-133 mg L) and solubilize phosphate (65-148 mg L). In a pot experiment, the inoculation of isolates NSX2 and LCR1 significantly enhanced the growth of and uptake of Cd by the Cd hyperaccumulator S. plumbizincicola. 454 pyrosequencing revealed that the inoculation of the PGPR lead to a decrease in microbial community diversity in the rhizopshere during phytoextraction. Specifically, indigenous heavy metal-tolerant PGPR such as Actinospica, Bradyrhizobium, Rhizobium, Mesorhizobium, and Mycobacterium were selectively enriched in the treatments in which PGPR were added. It is suggested that a unique constitution of microbial communities in inoculated treatments plays a key role in enhancing Cd phytoremediation. Conclusion: Inoculation of strains Rhodococcus erythropolis NSX2 and Cedecea davisae LCR1 could promote S. plumbizincicola growth and enhance the remediation efficiency. The introduced PGPR could also affect the indigenous microbial community structure and the diversity in Cd-contaminated soil during phytoremediation. [ABSTRACT FROM AUTHOR]

Bamboo shoots are highly nutritious but possess poor shelf life after harvest due to rapid decline of tenderness mostly result from lignification processes. Present investigation was performed to evaluate the potential of gamma radiation as a postharvest technology to preserve bamboo shoots. The effects of 0.5 kGy gamma radiation on quality and lignification of bamboo shoots during storage at 2 °C were investigated. The results showed that gamma radiation reduced the decay rate of bamboo shoots by 71% at the end of storage. It also significantly retarded ethylene production through controlling the activities of ACC synthase (ACS) and ACC oxidase (ACO), which may contribute to inhibition of lignin synthesis. Meanwhile, gamma radiation decreased the activities of phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD), which are associated with lignin accumulation, thus reduced lignin content by 12.5% than that of the control after twenty-eight days of storage. These results demonstrated the potential of the gamma radiation as a promising postharvest technique to maintain the quality and inhibit the lignification of bamboo shoots. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) generated by NADPH oxidases or apoplastic peroxidases play an important role in the plant defense response. Diminished expression of at least two Arabidopsis thaliana peroxidase encoding genes, PRX33 ( At3g49110 ) and PRX34 ( At3g49120 ), as a consequence of anti-sense expression of a heterologous French bean peroxidase gene ( asFBP1.1 ), were previously shown to result in reduced levels of ROS following pathogen attack, enhanced susceptibility to a variety of bacterial and fungal pathogens, and reduced levels of callose production and defense-related gene expression in response to the microbe associated molecular pattern (MAMP) molecules flg22 and elf26. These data demonstrated that the peroxidase-dependent oxidative burst plays an important role in the elicitation of pattern-triggered immunity (PTI). Further work reported in this paper, however, shows that asFBP1.1 antisense plants are not impaired in all PTI-associated responses. For example, some but not all flg22-elicited genes are induced to lower levels by flg22 in asFPB1.1 , and callose deposition in asFPB1.1 is similar to wild-type following infiltration with a Pseudomonas syringae hrcC mutant or with non-host P. syringae pathovars. Moreover, asFPB1.1 plants did not exhibit any apparent defect in their ability to mount a hypersensitive response (HR). On the other hand, salicylic acid (SA)-mediated activation of PR1 was dramatically impaired in asFPB1.1 plants. In addition, P. syringae -elicited expression of many genes known to be SA-dependent was significantly reduced in asFBP1.1 plants. Consistent with this latter result, in asFBP1.1 plants the key regulator of SA-mediated responses, NPR1, showed both dramatically decreased total protein abundance and a failure to monomerize, which is required for its translocation into the nucleus. [ABSTRACT FROM AUTHOR]

Rationale: In addition to the negative and positive symptoms of schizophrenia, cognitive deficits, including prefrontal cortical dysfunction, are now recognized as core features of this disorder. Compounds increasing the NMDA receptor function via the strychnine-insensitive glycine receptors have been proposed as potential antipsychotics. Depending on the ambient concentrations of glutamate and glycine, 1-aminocyclopropanecarboxylic acid (ACPC) behaves as either a partial agonist or a functional antagonist at the strychnine-insensitive glycine receptors. Objectives: We investigated the procognitive and antipsychotic-like effects of ACPC in rats treated with phencyclidine (PCP) or ketamine (KET), compounds that produce psychotic-like symptoms in humans and laboratory animals. Methods: Cognitive effects were investigated in the novel object recognition (NOR) and attentional set-shifting tests (ASST). In addition, the effects of ACPC were investigated in PCP-induced hyperactivity, conditioned avoidance response (CAR), and prepulse inhibition (PPI) tests. The effects on attention and impulsivity were measured in the five-choice serial reaction time task (5-CSRTT). Results: ACPC (200-400 mg/kg) inhibited memory fading in naive rats and like clozapine prevented PCP- and KET-induced amnesia in the NOR. In naive animals, ACPC at 400 but not 200 mg/kg enhanced cognitive flexibility in the ASST, as the animals required fewer trials to reach the criteria during the extra-dimensional phase. In contrast, ACPC did not affect PCP-induced hyperactivity, CAR, and PPI as well as attention and impulsivity in the 5-CSRTT. Conclusion: The present study demonstrates that ACPC enhanced both object recognition memory and cognitive flexibility dependent on the prefrontal cortex, but did not affect impulsivity nor exhibit an antipsychotic-like profile. [ABSTRACT FROM AUTHOR]