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Abstract: Expansins are cellular proteins expressed in the course of cell wall loosening during fruit ripening. There is no information about the relationship between expansins and ripening of chilling injury (CI)-affected banana fruit. Banana fruit were pre-treated with 0 or 1000μL/L propylene (functional ethylene analogue) for 16h and then stored at 7°C. CI symptoms of untreated control fruit appeared after 4 days, while propylene pre-treated fruit showed CI symptoms after 7 days. Thus, stimulation of ripening with propylene applied prior to storage at low temperature tended to alleviate CI. The fruit were stored for 8 days at 7°C and then transferred to 22°C, followed by treatment with 1000μL/L propylene to initiate ripening. The propylene treatment accelerated color change, increased ethylene production rate and caused a more rapid decrease in peel and pulp firmness. Two banana expansins, AY083168 and AF539540 (GeneBank), were chosen as the target genes MaExp1 and MaExp2, respectively. RNA blotting analysis showed no accumulation of either MaExp1 or MaExp2 transcripts in banana fruit during low temperature storage. Expansin genes were expressed more intensively in propylene pre-treated fruit than in control fruit upon removal from cold storage for propylene-initiated ripening. The results suggest that increased tolerance of banana fruit pre-treated with propylene to low temperature-induced chilling was related to higher post-storage ethylene production rates and enhanced expression of MaExp1 and MaExp2. [Copyright &y& Elsevier]

The ethylene insensitive 3/ethylene insensitive 3‐like (EIN3/EIL) plays an indispensable role in fruit ripening. However, the regulatory mechanism that links post‐translational modification of EIN3/EIL to fruit ripening is largely unknown. Here, we studied the expression of 13 MaEIL genes during banana fruit ripening, among which MaEIL9 displayed higher enhancement particularly in the ripening stage. Consistent with its transcript pattern, abundance of MaEIL9 protein gradually increased during the ripening process, with maximal enhancement in the ripening. DNA affinity purification (DAP)‐seq analysis revealed that MaEIL9 directly targets a subset of genes related to fruit ripening, such as the starch hydrolytic genes MaAMY3D and MaBAM1. Stably overexpressing MaEIL9 in tomato fruit hastened fruit ripening, whereas transiently silencing this gene in banana fruit retarded the ripening process, supporting a positive role of MaEIL9 in fruit ripening. Moreover, oxidation of methionines (Met‐129, Met‐130, and Met‐282) in MaEIL9 resulted in the loss of its DNA‐binding capacity and transcriptional activation activity. Importantly, we identified MaEIL9 as a potential substrate protein of methionine sulfoxide reductase A MaMsrA4, and oxidation of Met‐129, Met‐130, and Met‐282 in MaEIL9 could be restored by MaMsrA4. Collectively, our findings reveal a novel regulatory network controlling banana fruit ripening, which involves MaMsrA4‐mediated redox regulation of the ethylene signaling component MaEIL9. [ABSTRACT FROM AUTHOR]

Cell wall polysaccharides (CWP) are an important component of cell structure, and its content variation is a primary factor affecting the texture of fresh longan. The influences of dicyclohexylcarbodiimide (DCC) and disodium succinate (DS) treatments on the pulp softening and pulp breakdown, and their relation to CWP metabolism in pulp of longan fruit were explored. Compared with the control longan, DCC-treated fruit showed lower value of pulp firmness, higher index of pulp breakdown, higher expression levels of cell wall disassembly enzymes (CWDEs)-related genes (DlPME1 , DlPME3 , DlPG1, Dlβ-Gal1, Dlβ-Gal16 , DlCx7 , DlXET3 , DlXET27), and higher activities of CWDEs including pectin methyl esterase (PME), polygalacturonase (PG), β -galactosidase (β -Gal), cellulase (Cx), xyloglucan endotransglycosylase (XET), lower values of cell wall materials, and lower levels of CWP including ionic-soluble pectin, covalent-soluble pectin, cellulose, and hemicellulose. Whereas, the opposite effects were exhibited in DS-treated fruit. The above data indicate that DCC-hastened longan pulp softening and pulp breakdown was due to the up-regulating expressions of CWDEs-related genes, the activating activities of CWDEs, and the accelerating CWP disassembly by DCC treatment. Whereas, DS repressed longan pulp softening and pulp breakdown through down-regulating the expressions of CWDEs-related genes, inhibiting CWDEs activities, and reducing CWP degradation. • DCC accelerated longan pulp breakdown and softening process. • DS suppressed longan pulp breakdown and softening process. • DCC promoted cell wall degradation of longan pulp but DS showed opposite effect. • DCC raised gene expression and enzyme activity related to cell wall degradation. • DS reduced gene expression and enzyme activity related to cell wall degradation. [ABSTRACT FROM AUTHOR]

Compared to the control longan, DNP treatment elevated pulp breakdown index, reduced the values of pulp firmness, CSP, ISP, cellulose, and hemicellulose by enhancing the activities of PE, PG, Cx, XET, and β -Gal. Additionally, DNP treatment increased the levels of PLD, lipase, LOX, PA, and SFA, and decreased the values of PC, PI, USFA, U/S, and IUFA, displaying higher cell membrane permeability and more severe cell membrane damage in longan pulp. Furthermore, DNP treatment weakened the levels of SOD, CAT, APX, AsA, GSH, TP, and TF, thereby exacerbating ROS outbreak and MDA production. These results indicate that DNP treatment destroyed the antioxidant system to cause ROS eruption. This disruption further disturbed the metabolisms of membrane lipids and cell wall polysaccharides, leading to the breakdown of cell membrane and cell wall, and eventually aggravated longan pulp softening and breakdown. However, ATP treatment exhibited the opposite effects of DNP treatment. • Longan pulp breakdown and softening were accelerated by DNP but retarded by ATP. • Longan pulp's cell membrane and cell wall were damaged by DNP but reinforced by ATP. • The antioxidant system balance in longan pulp was impaired by DNP but defended by ATP. • Cell wall metabolism in longan pulp was enhanced by DNP but postponed by ATP. • Membrane lipid metabolism in longan pulp was accelerated by DNP but delayed by ATP. [ABSTRACT FROM AUTHOR]

Bananas are good sources of nutrients, magnesium and vitamins, and they are also rich in many antioxidant compounds, such as flavonoids. Flavonoids are secondary metabolites with antioxidant properties that play an effective role in detoxification of reactive oxygen species (ROS). Stresses, such as low temperature stress, lead to excessive accumulation of ROS and stimulate the increase of activity of enzymes and genes related to flavonoid biosynthesis and thereby the flavonoid contents in a variety of plants. However, the mechanism underlying the transcriptional regulation of flavonoids production in banana fruit under chilling injury (CI) remains largely unknown. In this study, we found that both the contents of phloretin, naringenin chalcone and dihydrokaempferol (a member of the flavanonols) and the expression levels of chalcone and flavanonol biosynthesis genes MaCHSs and MaF3Hb significantly increased in banana peels during CI. It is vital that these genes expression levels and flavonoid contants contain remarkabe positive correlations. Additionally, a key myeloblastosis (MYB) transcriptional inhibitor MaMYB4, a homologue of AtMYB4 involved in flavonoids biosynthesis, was negatively correlated to the accumulated phloretin, naringenin chalcone, and dihydrokaempferol. MaMYB4 could bind to AC-rich elements in the promoters of MaCHSs and MaF3Hb to repress their transcriptional activities. However, the expression level of MaMYB4 is down-regulated in banana peels during CI. As a result, MaCHSs and MaF3Hb were released and activated, leading to the production of naringenin chalcone and dihydrokaempferol in banana peels. Taken together, our findings unveil an interesting transcriptional module in relation to flavonoid accumulation in peels of banana under chilling stress. • Flavonoids accumulated in peels of banana fruits. • Phloretin, naringenin chalcone and dihydrokaempferol increased in banana peels under CI. • Expression level of MaCHSs was correlated to the contents of phloretin, naringenin chalcone and dihydrokaempferol. • MaMYB4 binds to the promoters of MaCHSs and MaF3Hb to take action. [ABSTRACT FROM AUTHOR]

Abstract: Polygalacturonase (PG), which degrades pectin in cell wall, was proposed to participate in the process of plant organ abscission. In an effort to understand the molecular mechanisms of lychee fruitlet abscission, a full-length cDNA encoding a polygalacturonase, termed as LcPG1, was isolated from lychee by using RT-PCR and RACEs. The LcPG1 cDNA was 1666bp in length with an open reading frame (ORF) of 1443bp, encoding a polypeptide of 481 amino acid residues. Homologous and phylogenetic analysis showed that the LcPG1 included three of the four typical domains conserved in PG proteins, and was clustered into the clade E of PG genes. Expression analysis in the fruitlet abscission zone (AZ) indicated that the expression of LcPG1 was positively correlated with the lychee fruitlet abscission, either induced by ethephon or inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D). Moreover, the carbohydrate stress caused by the girdling plus defoliation was found to stimulate the fruitlet abscission, which was paralleled with an increase in LcPG1 expression level. All these results suggested that the LcPG1 played an essential role in the process of lychee fruitlet abscission. To our knowledge, it is the first case indicating that a PG gene, belonging to the clade E, is involved in organ shedding. [Copyright &y& Elsevier]

Starch is the major constituent of green banana fruit and is a resource for banana quality as it is degraded to soluble sugars during postharvest ripening. However, the molecular basis of starch degradation in different banana cultivars during fruit ripening remains largely unclear. In this study, the starch degradation of four banana cultivars (Baxi, Dajiao, Fengjiao, Gongjiao) during ripening was investigated. The contents of total starch, amylase, amylopectin, the amylose/amylopectin ratio, and the crystallinity were all decreased in all the four banana cultivars tested. In addition, the morphological structures of starch granules changed as ripening progressed due to starch degradation. The activity and gene expression of starch hydrolytic enzymes were increased. Importantly, a transcriptional regulator MabZIP21 was identified, which functions as an activator of starch degradation by upregulating the transcription of MaBAM4 , MaBAM7 , and MaAMY3. In addition, transient overexpression of MabZIP21 in banana or overexpression of MabZIP21 in tomato increased starch corruption by elevating the accumulation of starch degrading genes. Through this study, we expect to show that distinct patterns of starch degradation exist in different banana cultivars, and that MabZIP21 mediates starch breakdown by transcriptional activation of MaBAM4 , MaBAM7 , and MaAMY3. ● Starch breaks down during the ripening of banana fruit. ● Starch crystallinity and starch granule size decreased during ripening. ● Amylase and isoamylase activities and transcripts increased in ripening bananas. ● MabZIP21 trans-activates the transcription of MaBAM4 , MaBAM7 and MaAMY3. [ABSTRACT FROM AUTHOR]

Linoleic acid (LA; C18:2) and α-linolenic acid (ALA; C18:3) are two essential unsaturated fatty acids that play indispensable roles in maintaining membrane integrity in cold stress, and ω-3 fatty acid desaturases (FADs) are responsible for the transformation of LA into ALA. However, how this process is regulated at transcriptional and posttranscriptional levels remains largely unknown. In this study, an MYB transcription factor, MaMYB4, of a banana fruit was identified and found to target several ω-3 MaFADs , including MaFAD3-1 , MaFAD3-3 , MaFAD3-4 and MaFAD3-7 , and repress their transcription. Intriguingly, the acetylation levels of histones H3 and H4 in the promoters of ω-3 MaFADs were elevated in response to cold stress, which was correlated with the enhancement in the transcription levels of ω-3 MaFADs and the ratio of ALA/LA. Moreover, a histone deacetylase MaHDA2 physically interacted with MaMYB4, thereby leading to the enhanced MaMYB4-mediated transcriptional repression of ω-3 MaFADs. Collectively, these data demonstrate that MaMYB4 might recruit MaHDA2 to repress the transcription of ω-3 MaFADs by affecting their acetylation levels, thus modulating fatty acid biosynthesis. Our findings provided new molecular insights into the regulatory mechanisms of fatty acid biosynthesis in cold stress in fruits. [ABSTRACT FROM AUTHOR]

• High temperature elevates carotenoid accumulation of banana. • High temperature induces expression of MaEIL9 and carotenogenic genes. • MaEIL9 targets promoters of carotenogenic genes and MaSPL16. • Overexpression of MaEIL9 in tomato enhances carotenoid production. Banana is a good source of carotenoids, which are bioactive metabolites with health beneficial properties for human. However, the molecular mechanism of carotenoid accumulation in banana fruit is largely unclear. In this study, we found that high temperature elevated carotenoid production in banana pulp, which is presumably due to upregulation of a subset of carotenogenic genes as well as a carotenoid biosynthesis regulator MaSPL16. Moreover, an ethylene signaling component MaEIL9 was identified, whose transcript and protein contents were also induced by high temperature. In addition, MaEIL9 positively regulates transcription of MaDXR1 , MaPDS1 , MaZDS1 and MaSPL16 through directly targeting their promoters. Overexpression of MaEIL9 in tomato fruit substantially increased the expression of carotenoid formation genes and elevated carotenoid content. Importantly, transiently silencing MaEIL9 in banana fruit weakened carotenoid production caused by high temperature. Taken together, these results indicate that high temperature induces carotenoid production in banana fruit, at least in part, through MaEIL9-mediated activation of MaDXR1 , MaPDS1 , MaZDS1 and MaSPL16 expression. [ABSTRACT FROM AUTHOR]

Banana is an important source of carotenoids, and the fruit accumulate carotenoids during the ripening process. However, the regulatory mechanisms underlying carotenoid production in banana fruit have not been well studied. Here, we report that MaERF124 is a negative transcriptional regulator of carotenogenesis genes in banana. The reduced accumulation of MaERF124 was accompanied with the increased contents of carotenoids during the ripening of the four banana varieties, suggesting a negative role of MaERF124 in carotenoid production. Further assays showed that MaERF124 acts as a transcriptional repressor and directly targets the promoters of carotenoid biosynthetic genes including MaDXR , MaGGPS , MaCRTISO and MaLCYB1.2. Moreover, ectopic expression of MaERF124 in tomato fruit repressed the transcript levels of carotenoid formation genes to inhibit carotenoid production. Taken together, these findings reveal that MaERF124 negatively modulates carotenoid formation via transcriptional repression of key genes involved in carotenoid synthesis, which provides a regulatory machinery for improving the contents of carotenoids in banana fruit. • Reduced expression of MaERF124 is inversely associated with carotenoid accumulation. • MaERF124 acts as a transcriptional repressor. • MaERF124 suppresses the transcription of carotenogenesis genes. • Overexpression of MaERF124 in tomato inhibits carotenoid production. [ABSTRACT FROM AUTHOR]

Ethylene is essential for the ripening of climacteric fruit such as banana, but the transcriptional modulation of ethylene formation in ripening banana is not well studied. In this work, two WRKY transcription factors MaWRKY49 and MaWRKY111 were identified from banana fruit. MaWRKY49 and MaWRKY111 were both nucleus-localized transcriptional activators, the transcription of which continued to increase following banana fruit ripening. MaWRKY49 and MaWRKY111 not only stimulated the transcription of themselves to constitute the feedback regulatory loop, but also promoted the transcription of ethylene biosynthesis genes MaACS1 and MaACO1 by directly targeting the W-box elements. Moreover, MaWRKY49 and MaWRKY111 interacted with each other to form the heterodimer, contributing to further enhancement of their target gene transcription. Importantly, both MaWRKY49 and MaWRKY111 interacted with another transcriptional activator MabZIP21, which synergistically strengthened the transcription of MaACS1 and MaACO1. Collectively, our findings suggest that MaWRKY49 and MaWRKY111 cooperate with MabZIP21 to positively regulate the ripening of banana by promoting transcription of ethylene biosynthesis genes MaACS1 and MaACO1. • MaWRKY49/111 transcactivate the transcription of MaACS1 , MaACO1 and themselves. • MaWRKY49 physically interacts with MaWRKY111. • MaWRKY49/111 interact with another transcriptional regulator MabZIP21. • Interaction between MaWRKY49/111 and MabZIP21 enhances target gene transcription. [ABSTRACT FROM AUTHOR]

BREVIPEDICELLUS (BP or KNAT1), a class-I KNOTTED1-like homeobox (KNOX) transcription factor in Arabidopsis thaliana, contributes to shaping the normal inflorescence architecture through negatively regulating other two class-I KNOX genes, KNAT2 and KNAT6. However, the molecular mechanism of BP-mediated transcription regulation remains unclear. In this study, we showed that BP directly interacts with the SWI2/SNF2 chromatin remodeling ATPase BRAHMA (BRM) both in vitro and in vivo. Loss-of-function BRM mutants displayed inflorescence architecture defects, with clustered inflorescences, horizontally orientated pedicels, and short pedicels and internodes, a phenotype similar to the bp mutants. Furthermore, the transcript levels of KNAT2 and KNAT6 were elevated in brm-3, bp-9 and brm-3 bp-9 double mutants. Increased histone H3 lysine 4 tri-methylation (H3K4me3) levels were detected in brm-3, bp-9 and brm-3 bp-9 double mutants. Moreover, BRM and BP co-target to KNAT2 and KNAT6 genes, and BP is required for the binding of BRM to KNAT2 and KNAT6. Taken together, our results indicate that BP interacts with the chromatin remodeling factor BRM to regulate the expression of KNAT2 and KNAT6 in control of inflorescence architecture. [ABSTRACT FROM AUTHOR]

Fruit softening is an ethylene-dependent ripening event. 1-Methylcyclopropene (1-MCP), a synthetic plant growth regulator structurally related to the natural plant hormone ethylene, is used to slow down the fruit ripening. However, inappropriate 1-MCP treatment tends to cause the elastic texture in papaya fruit. Constitutive triple response 1 (CTR1), a downstream protein of the ethylene receptors, acts as a negative regulator of ethylene signaling. To elucidate the signal transduction pathway involved in the ethylene regulation during papaya ripening and softening, four genes homologous to Arabidopsis CTR1 were isolated from papaya fruit and designated as CpCTR1- 4. Their molecular and biochemical properties were characterized, and their expression patterns in papaya fruit after treatments with 1-MCP were investigated. Four CTR1-like genes differ in sequence length and molecular size, and have a relative distance relationship in the evolutionary tree analysis. However, sequences analysis showed that the C-terminus of CpCTR1- 4 proteins contained the highly conserved kinase domains, including a protein kinase ATP-binding signature (IGAGSFGTVH) and a serine/threonine protein kinase active site signature (IVHRDLKSPNLLV). Their N-terminus contains the conserved motifs (CN box) that exist in all CTR1-like proteins. CpCTR1-4 proteins were predicted to be located differently in either chloroplast or nuclei or both. Gene expression analysis showed that 1-MCP treatment significantly repressed the expression of CpCTRs and high concentration of 1-MCP treatment had a more significant effect. These results suggested that CpCTR1-4 genes may play different roles in papaya fruit ripening and softening and that the rubbery fruit might be relate to the expression of CpCTRs genes. [ABSTRACT FROM AUTHOR]

Abstract: Ethylene response factors (ERFs) play important roles in fruit development, ripening, defense responses and stress signaling pathways. After harvest, climacteric fruit such as papaya are subject to a range of problems associated with postharvest handling and storage treatments. There have been few attempts to evaluate the role of ERFs in fruit's responses to environmental stimuli. To investigate the transcriptional mechanisms underlying fruit developmental, ripening and stresses, we cloned four ERFs from papaya. The deduced amino acid sequence of CpERFs contained the conserved apetalous (AP2)/ERF domain, which shared high similarity with other reported AP2/ERF domains. The phylogeny, gene structures, and putatively conserved motifs in papaya ERF proteins were analyzed, and compared with those of Arabidopsis. Expression patterns of CpERFs were examined during fruit development, under 1-MCP treatment, ethephon treatment, biotic stress (temperature stress) and pathogen stress. CpERFs displayed differential expression patterns and expression levels under different experimental conditions. CpERF2 and CpERF3 showed a close association with fruit ripening and CpERFs had a high expression level in the earlier stages during the fruit development period. The expression of CpERFs strongly associated with stress response. These results support the role for papaya ERFs in transcriptional regulation of ripening-related or stress-respond genes and thus, in the regulation of papaya fruit-ripening processes and stress responses. [Copyright &y& Elsevier]

Abstract: Δ1-Pyrroline-5-carboxylate synthetase (P5CS) catalyzes the rate-limiting step in proline biosynthesis in plants. In the present study, a full-length cDNA, denominated as CpP5CS2 for Δ1-pyrroline-5-carboxylate synthetase (P5CS), was cloned from papaya using in silico cloning and 3′- or 5′-rapid amplification of cDNA ends (RACE). The full-length cDNA of CpP5CS2 was 2583bp, with a 2151bp open reading frame (ORF) encoding a 717 amino acid polypeptide. Sequence analysis showed that CpP5CS2 contained several substrate-binding and catalytic domains and had high homology to other plant P5CSs. The expression pattern of CpP5CS2 in papaya under low (7°C) and high temperature (35°C) stresses was examined using real-time quantitative PCR. The results showed that both stresses induced CpP5CS2 expression during the storage period, and the increased expression of CpP5CS2 preceded proline accumulation. In addition, the high temperature caused a more significant induction of CpP5CS2 expression and a higher level of accumulated proline than low temperature. [Copyright &y& Elsevier]

Abstract: Storage and transport of litchi fruit at low temperature is widely practiced commercially. In this study, no pericarp browning was evident at out-turn on litchi fruit stored for 10 and 20 days at cold temperature of 3–5°C, but fruit stored for 10 days at 3–5°C gradually browned after 12h of shelf time at ambient temperature of 25°C, with the browning index (BI) being elevated to 2.5 at 24h of shelf life. Furthermore, fruit stored for 30 days began to rot and had a decay incidence of about 30% after 24h on the shelf. The temperature increment from 3–5 to 25°C induced marked increases in activities of lipase, phospholipase D (PLD) and lipoxygenase (LOX). Litchi fruit stored for 10 days at 3–5°C followed by the shelf time at 25°C had lower activities of lipase, PLD and LOX, and also lower levels of membrane permeability, than did fruit stored for 20 and 30 days. Energy level of the pericarp tissue of cold-stored litchi fruit was similarly dependent on storage time at 3–5°C plus shelf time at 25°C. Adenosine triphosphate (ATP) content and adenylate energy charge (AEC) level in pericarp tissues decreased as cold storage progressed. However, ATP and adenosine diphosphate (ADP) contents, and the AEC levels, in cold-stored litchi fruit increased during shelf time at 25°C, reaching a peak after 6h, and then decreasing. Fruit stored for 30 days at 3–5°C had much lower ATP content and AEC level than fruit stored for 10 and 20 days. Increased activities of lipase, PLD and LOX, and energy shortage in cold-stored pericarp tissues during subsequent shelf time at 25°C suggest that the deterioration of membrane integrity and loss of compartmentation gives rise to accelerated browning and fruit quality deterioration. [Copyright &y& Elsevier]

• Ethylene alleviates CI of banana. • Ethylene inhibits MabHLH060/183 expression. • MabHLH060/183 target the promoters of PA formation genes. Chilling injury (CI) of banana represents a serious problem constraining postharvest preservation in the industry. Application of ethylene was found to efficiently attenuate CI of banana, however, the mechanism of which remains to be investigated. Here, we found that application of ethrel could ameliorate the CI of banana, as evidenced by lower CI index, electrolytic leakage and malondialdehyde content. Meanwhile, expression of phosphatidic acid (PA) formation genes MaPLDδ1 , MaPLDδ5 and MaDGK2 , as well as two transcriptional regulators MabHLH060 and MabHLH183 was significantly increased with the progression of CI, but decreased under ethrel treatment. MabHLH060 and MabHLH183 were shown to locate in nucleus and have transactivation ability. Importantly, these two transcriptional regulators MabHLH060/183 recognized the E-box elements in the promoters of MaPLDδ1 , MaPLDδ5 and MaDGK2 , and promoted their transcription. Together, these findings suggest that ethylene-alleviated CI of banana may involve the MabHLH060/183 module in modulating the expression of PA formation genes. [ABSTRACT FROM AUTHOR]

Abstract: Pectin is one of the major components of the primary cellular walls and middle lamella in plant tissues. In this study, water-soluble pectin (WSP) and acid-soluble pectin (ASP) fractions were isolated from pulp tissues of banana fruit at various ripening stages. Their monosaccharide compositions, glycosyl linkages and molecular mass distributions were evaluated. As ripening progressed, fruit firmness decreased rapidly, which was associated with the increase in the WSP content and the decrease in the ASP content. Meanwhile, the molecular mass distributions of WSP and ASP fractions exhibited a downshift tendency, indicating the disassembly of pectin polysaccharides. Moreover, galactose and galacturonic acid as the major monosaccharide compositions of pectin polysaccharides increased in WSP fraction but decreased in ASP fraction during fruit softening. GC–MS analysis further revealed that pectin polysaccharide had a 1,4-linked galactan/galacturonan backbone with different types of branching and terminal linkages in WSP and ASP fractions. During banana fruit ripening, the amount of 1,4-linked Galp residues of ASP fraction decreased significantly whereas 1,3,6-linked Galp, 1,2-linked Manp and 4-linked Araf residues disappeared, which was related to depolymerization of pectin polysaccharides. Overall, the study indicated that the modifications in polysaccharide compositions and glycosyl linkages, reduced molecular mass distributions and enhanced depolymerization of pectin fraction during banana ripening were responsible for fruit softening. [Copyright &y& Elsevier]

Abstract: Fruit softening is generally attributed to cell wall disassembly. Experiments were conducted to investigate effects of various reactive oxygen species (ROS) on in vitro cellular wall disassembly of harvested banana fruit. The alcohol-extracted insoluble residue (AEIR) was obtained from the pulp tissues of banana fruit at various ripening stages and then used to examine the disassembly of cellular wall polysaccharides in the presence of superoxide anion (), hydrogen peroxide (H2O2) or hydroxyl radical ( OH) and their scavengers. The presence of OH accelerated significantly disassembly of cellular wall polysaccharides in terms of the increase in contents of total sugars released and uronic acid, and the decrease in molecular mass of soluble polysaccharides, using gel permeation chromatography. However, the treatment with H2O2 or showed no significant effect on the disassembly of cellular wall polysaccharides. Furthermore, the degradation of the de-esterified AEIR was more susceptible to OH attack than the esterified AEIR. In addition, the effect of OH could be inhibited in the presence of OH scavenger. This study suggests that disassembly of cellular wall polysaccharides could be initiated by OH as the solublisation of the polysaccharides increased, which, in turn, accelerated fruit softening. [Copyright &y& Elsevier]

Abstract: Exogenous ethylene inhibits floral opening in cut rose (Rosa hybrida) cv. Kardinal and slightly promotes opening in cv. Samantha. We investigated ethylene production following short exposure to exogenous ethylene, and the expression of ethylene receptor genes (ETR) and genes in the ethylene signal transduction pathway (CTR and EIN3). In cv. Kardinal the ethylene production rate was much higher than in cv. Samantha, following ethylene treatment. The expression of ETR fragments was not much affected by ethylene in cv. Kardinal but was up-regulated in cv. Samantha. Data from the literature suggest that ETR is a negative regulator. The up-regulation of ETR, after ethylene treatment, indicates that the sensitivity to ethylene is down-regulated in Samantha but not in Kardinal. No clear effect of ethylene was found on the expression of fragments of CTR and EIN3 genes. It is concluded that the inhibition of floral opening in cv. Kardinal, and its absence in cv. Samantha, can apparently be explained by a differential effect of ethylene on the expression of genes for the ethylene receptor. [Copyright &y& Elsevier]

[Display omitted] • Low temperature (LT) leads to abnormal ripening and poor quality of postharvest banana fruits. • The effect of LT pre-storage on gene expression in pulp samples was evaluated. • Differentially expressed genes (DEGs) analysis identified 9 MYBs and 32 fruit ripening-associated genes. • A potential linkage between the above MYBs and ripening-related genes was proposed. Low temperature leads to abnormal ripening and poor quality of the harvested banana fruit, which is an urgent problem limiting the development of industry in China. To comprehensively understand the mechanism underlying low-temperature-affected ripening, we performed comparative RNA-Seq analysis of ethylene-induced ripening of banana fruit after 3 days of pre-storage at 7 °C and 22 °C. A total of 986 differentially expressed genes (DEGs) were identified in both RT-0 d versus RT-3 d, LT-0 d versus LT-3 d, RT-0 d versus LT-0 d and RT-3 d versus LT-3 d, and the RNA-Seq outputs of 15 randomly selective DEGs were verified using qRT-PCR. Among the 986 DEGs obtained in the four groups, 9 MYB genes (MaMYB75/281/219/4/151/156/3/37 and MaMYB3R1) and 32 genes related to carotenoid biosynthesis (MaPSY1/2a), flavor formation (MaLOX6 , MaADH7 , MaAAT1), sucrose transport (MaSUS2/4), ethylene production (MaSAM1 , MaACO9/10/12 , MaACS1/12), starch degradation (MaAMY1A/1B , MaPHS1/2 , MaMEX2 , MapGlcT1) and cell wall degradation (MaPG3/X1 , MaPME25/41 , MaXTH5/7/22/23/25 , MaEXP2/20/A1/A15) were characterized. Combining transcription factor binding site (TFBS) analysis as well as cis -acting element analysis, the regulatory network of low-temperature-affected ripening mediated by MYBs were constructed. The data generated in this study may unravel the transcriptional regulatory network of MYBs associated with low-temperature-affected ripening and provide a solid foundation for future studies. [ABSTRACT FROM AUTHOR]

• Lasiodiplodia theobromae induced disease development of harvested longan fruit. • L. theobromae stimulated fruit softening and displayed lower fruit firmness of longan. • L. theobromae promoted degradation of cell wall polysaccharides in longan pericarp. • L. theobromae enhanced cell wall-disassembling enzymes activities in longan pericarp. • L. theobromae boosted disease development via disassembling cell wall polysaccharides. Cell wall polysaccharides in fruits act a pivotal role in their resistance to fungal invasion. Lasiodiplodia theobromae (Pat.) Griff. & Maubl. is a primary pathogenic fungus causing the spoilage of fresh longan fruit. In this study, the influences of L. theobromae inoculation on the disassembly of cell wall polysaccharides in pericarp of fresh longans and its association with L. theobromae -induced disease and softening development were investigated. In contrast to the control, samples with L. theobromae infection showed more severe disease development, lower firmness, lower amounts of cell wall materials, covalent-soluble pectin, ionic-soluble pectin, cellulose and hemicellulose, whereas higher value of water-soluble pectin, higher activities of cell wall polysaccharide-disassembling enzymes (cellulase, β -galactosidase, polygalacturonase and pectinesterase). These findings revealed that cell wall polysaccharides disassembly induced by enzymatic manipulation was an essential pathway for L. theobromae to infect harvested longans, and thus led to the disease occurrence and fruit softening. [ABSTRACT FROM AUTHOR]

Low-temperature storage is a common strategy for preserving and transporting vegetables and fruits. However, many fruits are hypersensitive to chilling injury, including bananas. In the present study, storage conditions of 11 °C delayed the ripening of Fenjiao (Musa ABB Pisang Awak) banana, and the pulp could be softened after ethephon treatment. Storage conditions of 7 °C prevented fruit from fully softening, and fruit contained a significantly higher starch content and lower soluble sugar content. MaEBF1, a critical gene component in the ethylene signaling pathway, was repressed during ripening after fruit had been stored for 12 days at 7 °C. The expression of a series of starch degradation-related genes and a MaNAC67-like gene were also severely repressed. Both MaEBF1 and MaNAC67-like genes were ethylene-inducible and localized in the nucleus. MaNAC67-like protein was able to physically bind to the promoter of genes associated with starch degradation, including MaBAM6, MaSEX4, and MaMEX1. Yeast two-hybrid, GST-pull down, and BiFC assays showed that MaEBF1 interacted with the MaNAC67-like protein, and their interaction further activated the promoters of MaBAM6 and MaSEX4. The current study indicates that MaNAC67-like is a direct regulator of starch degradation and potential for involvement in regulating chilling-inhibited starch degradation by interacting with the ethylene signaling components in banana fruit. The present work paves the way for further functional analysis of MaEBF1 and MaNAC67-like in banana, which will be useful for understanding the regulation of banana starch metabolism and fruit ripening. [ABSTRACT FROM AUTHOR]