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Plasmopara viticola , the casual oomycete of grapevine downy mildew, could cause yield loss and compromise berry quantity. Previously, we have identified several PvRXLR effectors that could suppress plant immunity to promote infection and disease development. In this study, the role of effector, PvRXLR53, in plant-microbe interaction was investigated. PvRXLR53 has several orthologs in other oomycetes and contains a functional signal peptide. Expression level of PvRXLR53 was already detected upon inoculation, further induced in the early stage after P. viticola inoculation and decreased to low level in the late infection stage in grapevine ( Vitis vinifera 'Cabernet Sauvignon'). PvRXLR53 is localized in both nucleus and cytoplasm. When transiently expressed in Nicotiana benthamiana , PvRXLR53 suppressed oomycete elicitor INF1-triggered programmed cell death and defense gene expression, and Phytophthora capsici -induced reactive oxygen species production (ROS) and eventually resistance to P. capsici . In summary, these findings suggest that P. viticola secretes PvRXLR53 to suppress host immunity from the very early stage of infection.

Height and leaf morphology are important agronomic traits of the major crop plant rice ( Oryza sativa ). In previous studies, the dwarf and narrow leaf genes ( dnl1, dnl2 and dnl3 ) have identified in rice. Using the Ac / Ds knockout system, we found a new dwarf and narrow leaf (dnl) mutant and identified mutated gene. The dnl-4 mutant showed reduced plant height and leaf blade width compared to the wild type, and increased leaf inclination. The morphological defects of the mutant were caused by the suppressed expression of the DNL-4 gene, which encodes a pfkB carbohydrate kinase protein. These results suggest that DNL-4 expression is involved in modulating plant height and leaf growth. Furthermore, DNL-4 expression also affects productivity in rice: the dnl-4 mutant exhibited reduced panicle length and grain width compared with the wild type. To understand DNL-4 function in rice, we analyzed the expression levels of leaf growth-related genes, such as NAL1, NAL7 , and CSLD4 , in the dnl-4 mutant. Expression of NAL1 and NAL7 was downregulated in the dnl-4 mutant compared to the wild type. The observation that DNL-4 expression corresponded with that of NAL1 and NAL7 is consistent with the narrow leaf phenotype of the dnl-4 mutant. These results suggest that DNL-4 regulates plant height and leaf structure in rice.

Circadian clock operates autonomously in each cell and drives the approximately 24-h rhythm in individual tissues and organs. It is known that the evening complex (EC) components and GI are required for ambient temperature perception and thermomorphogenesis in higher plants. Our previous study found that PRR9 and 7 are required for the lengthened period of the circadian rhythm in roots, and they are responsible for the temperature overcompensation in shoots. However, the molecular mechanism of the circadian clock, especially in different tissues, in response to temperature oscillations remains largely unknown. Here, we studied the transcript levels of EC genes and GI of the prr7 prr9 mutant shoots and roots in response to 22°C or 28°C, respectively. The results showed that PRR9 , 7 in roots inhibited the transcripts accumulation of ELF3, ELF4 , and LUX at 28°C. In addition, loss-of-function of both PRR9 and 7 caused an increase in GI expression at 22°C, but warm temperature of 28°C limited the negative effect of PRR9 , 7 on GI in roots. Our findings proposed a temperature-dependent molecular basis for root-specific circadian clock and indicated the critical role for PRR9 , 7 in negatively regulating ELF3, ELF4, LUX , and GI in the circadian gating of thermoresponse.

Brassicaceae plants, including Arabidopsis thaliana , develop endoplasmic reticulum (ER)-derived structures called ER bodies, which are involved in chemical defense against herbivores. NAI1 is a basic helix-loop-helix (bHLH) type transcription factor that regulates two downstream genes, NAI2 and BGLU23 , that are responsible for the ER body formation and function. Here, we examined the transcription factor function of NAI1, and found that NAI1 binds to the promoter region of NAI2 and activates the NAI2 promoter. The recombinant NAI1 protein recognizes the canonical and non-canonical G-box motifs in the NAI2 promoter. Furthermore, we examined the DNA binding activity of NAI1 toward several E-box motifs in the NAI2 and BGLU23 promoters and found that NAI1 binds to a DNA fragment that includes an E-box motif from the BGLU23 promoter. Subcellular localization of NAI1 was evident in the nucleus, which is consistent with its transcription factor function. Transient expression experiments in Nicotiana benthamiana leaves showed that GFP-NAI1 protein activated the NAI2 promoter by binding to the two G-boxes of the promoter. Disruption of the G-boxes abolished the NAI1-dependent activation of the NAI2 promoter. These results indicate that NAI1 has a DNA binding activity in a motif-dependent manner and suggest that NAI1 regulates NAI2 and BGLU23 gene expressions through binding to these DNA motifs in their promoters.

GmGASA is the GASA gibberellin regulated cysteine-rich protein family. The expression of GmGASA is up-regulated by gibberellin, which is the longest plant hormone in plants playing vital roles in plant development. However, very few reports explaining the direct regulation of downstream genes by GASA gene are available. In the current study, the GmGASA32 , a member of the GASA family affecting soybean height was identified. In the early stage, preliminary verification of the response of GmGASA32 to gibberellin through phenotypic experiment was done. The promoter activity analysis confirmed that GmGASA32 was induced by gibberellin. Subcellular localization showed that GmGASA32-GFP fusion protein enriched in the nucleus after gibberellin treatment. In order to confirm the function of GmGASA32 in the nucleus, we confirmed that the GASA domain in the C terminal of GmGASA32 can interact with GmCDC25 (cell cycle-associated protein) through the bimolecular fluorescence complementation (BiFC) assay.

Quantitative reverse transcription PCR (qRT-PCR) analysis and ProACO2::GUS expression showed that ACO2 was highly expressed in the shoots of Arabidopsis seedlings under light conditions. Exogenously applied aminocyclopropane-1-carboxylic acid (ACC) enhanced the expression of ACO2 , whereas Co 2+ ions suppressed its expression. In comparison with wild-type seedlings, the ACO2 knockdown mutant aco2-1 produced less ethylene, which resulted in the inhibited growth of Arabidopsis seedlings. Exogenously applied brassinolide reduced the expression of ACO2. ACO2 expression was increased in det2 , a brassinosteroid (BR)-deficient mutant; however, it was decreased in bes1-D , a brassinosteroid insensitive 1-EMS-suppressor 1 (BES1)-dominant mutant. In the putative promoter region of ACO2 , 11 E-box sequences for BES1 binding but not BR regulatory element sequences for brassinazole-resistant 1 (BZR1) binding were found. Chromatin immunoprecipitation assay showed that BES1 could directly bind to the E-boxes located in the putative promoter region of ACO4 . Less ethylene was produced in bes1-D seedlings compared with wild-type seedlings, suggesting that the direct binding of BES1 to the ACO2 promoter may negatively regulate ACO2 expression to control the endogenous level of ethylene in Arabidopsis seedlings.

Oat ( Avena sativa L.) is an important crop in northwestern China. Drought stress is the most significant factor affecting oat yield. In the present study, we explored the changes that occur in oats under drought stress conditions at a global genomic level. RNA sequencing was performed using 15-day-old oat seedlings. The differentially expressed transcripts were identified, and their related functions and pathways were investigated. In total, 1,065 unigenes were differentially expressed in oats under drought stress conditions. Of these, 386 unigenes were upregulated and 679 were downregulated. The perturbed transcripts were closely related to the biosynthesis of secondary metabolites, plant hormone signal transduction, and biosynthesis of antibiotics. DN50483_c0_g1_i3, which was annotated as acetyl-CoA carboxylase, was a significant node in the protein-protein interaction network. Biosynthesis of antibiotics and secondary metabolites may be involved in the drought stress response mechanisms of oats. The perturbed transcripts may provide targets for improving plant stress responses.

The Arabidopsis transcription factor Myeloblastosis protein 75 (MYB75, AT1G56650) is a well-established transcriptional activator of genes required for anthocyanin and flavonoid production, and a repressor of lignin and other secondary cell wall biosynthesis genes. MYB75 is itself tightly regulated at the transcriptional, translational and post-translational levels, including protein phosphorylation by Arabidopsis MAP kinases Examination of the behavior of different phosphovariant versions of MYB75 in vitro and in vivo revealed that overexpression of the MYB75 T131E phosphovariant had a particularly marked effect on global changes in gene expression suggesting that phosphorylated MYB75 could be involved in a broader range of functions than previously recognized. Here, we describe a range of distinct developmental phenotypes observed among Arabidopsis lines expressing various phosphovariant forms of MYB75. Expression of either MYB75 T131E or MYB75 T131A phosphovariants, from the endogenous MYB75 promoter, in Arabidopsis myb75 - mutants (Nossen background), resulted in severely impaired germination rates, and developmental arrest at early seedling stages. Arabidopsis plants overexpressing MYB75 T131E from a strong constitutive Cauliflower mosaic virus (CaMV35S) promoter displayed slower development, with delayed bolting, flowering and onset of senescence. Conversely, MYB75 T131A -overexpressing lines flowered and set seed earlier than either Col-0 WT controls or other MYB75 -overexpressors ( MYB75 WT and MYB75 T131E ). Histochemical analysis of mature stems also revealed ectopic vessel development in plants overexpressing MYB75 ; this phenotype was particularly prominent in the MYB75 T131E phosphovariant. These data suggest that MYB75 plays a significant role in plant development, and that this aspect of MYB75 function is influenced by its phosphorylation status.

Spliceosomes are large complexes regulating pre-mRNA processing in eukaryotes. Arabidopsis JANUS encodes a putative subunit of spliceosome`. We recently demonstrated that JANUS plays an essential role during early embryogenesis and root meristem development. Instead of mediating pre-mRNA splicing as a subunit of spliceosome, JANUS regulates the transcription of key genes by recruiting RNA Polymerase II (Pol II). Here, we summarize our latest findings and provide insights into the regulation of JANUS during Arabidopsis development.

As an important transcription factor family, GROWTH-REGULATING FACTORs ( GRFs ) are involved in central development processes, including growth regulation, insect and disease resistance, and stress response. The OsGRF7 has recently been shown involving in modulating leaf angle through regulating GA and IAA metabolism. Interestingly, we found that OsGRF7 negatively regulates the tiller number. However, the detailed molecular mechanisms of OsGRF7 underlying the tiller number determination are still not understood. Here, we report that OsGRF7 directly targets the promoter of the NODULATION SIGNALING PATHWAY2 ( OsNSP2 ), a key factor involving in the strigolactone synthesis. Correspondingly, OsGRF7 alters the expression level of OsNSP2 and the endogenous strigolactone content, which rendered repression of the outgrowth of the axillary buds. These findings unveil a novel function of OsGRF7 in rice tillering determination.

Calcium-dependent protein kinases-related kinases (CDPK-related kinases; CRKs) are Ser/Thr kinases that bind with Ca 2+ /Calmodulin and play crucial roles in signal transduction pathways during plant growth, development, and responses to multiple stresses. In this study, we have studied detailed organ and tissue-specific expression patterns of rice CRK genes. Our organ-specific RT-PCR analyzes show the differential expression pattern of these genes in various organs of rice. Moreover, our RNA-RNA in situ hybridization study in rice stem base containing developing crown root primordia demonstrates that the expression of CRK genes is spatially restricted to the developing crown root primordia, suggesting their putative role in protein phosphorylation-dependent cellular signaling during rice crown root development. Furthermore, organ-specific differentially expression pattern of CRK genes during floral organogenesis further support for the organ-specific cell signaling during organogenesis. Thus, our study provides a developmentally regulated expression pattern of rice CRK genes, though they are broadly expressed and a basic foundation for functional characterizations of CRK gene members to unravel their specific functions during plant growth and development.

Among all the major environmental challenges, drought stress causes considerable damage to plant growth and agricultural productivity. Drought stress directly promotes the accumulation of abscisic acid (ABA) via the activation of genes that encode enzymes involved in ABA biosynthesis, which protect the plant against water-limiting conditions. At the same time, the expression of genes that encode ABA-hydroxylases that inactivate the newly synthesized ABA, is repressed by drought stress. These phenomena occur through epigenetic modifications via the reversible processes of histone acetylation and deacetylation, also known as chromatin remodeling, which is an important regulatory mechanism that responds to various environmental stresses. Recently, we had reported that the chromatin remodeling complex HDA9-PWR-ABI4 promotes the development of drought tolerance through the deacetylation of CYP707A1/2 genes that encode the major enzymes involved in ABA catabolism. Here, we discuss the role of HDA9 and PWR in regulating drought stress by modulating the acetylation status of the CYP707A genes.

Iron (Fe) is an important micronutrient for plant growth and development but any excess of Fe is toxic because of the Fe-dependent generation of reactive oxygen species (ROS). Thus, Fe homeostasis must be tightly regulated. In Arabidopsis thaliana , a cascade of transcription factors has been identified as involved in the regulation of this process by modulating the expression of genes related to Fe uptake, transport, and storage. Recently, it was demonstrated that in response to Fe deficiency, bHLH121/URI (UPSTREAM REGULATOR OF IRT1) directly activates the expression of several genes involved in this regulatory network. It was also shown that bHLH121 interacts with ILR3 (bHLH105) and its homologs. Herein it is shown that bHLH121 is necessary for the expression of the main markers of the plant responses to Fe excess, the ferritin genes ( i.e. FER1, FER3 , and FER4 ). bHLH121 regulates ferritin genes expression by directly binding to their promoters, at the same locus than the ILR3-PYE repressive complex. Therefore, this study highlight that bHLH121, PYE, and ILR3 form a chain of antagonistic switches that regulate the expression of ferritin genes. The implication of this finding is discussed.

SABATH methyltransferases convent plant small-molecule metabolites into volatile methyl esters, which play important roles in many biological processes and defense reactions in plants. In this study, a total of 32 SABATH genes were identified in the Camellia sinensis var. sinensis (CSS) genome, which were renamed CsSABATH1 to CsSABATH32. Genome location annotation suggested that tandem duplication was responsible for the expansion of SABATH genes in tea plant. Multiple sequence alignment and phylogenetic analysis showed that the CsSABATHs could be classified into three groups (I, II and III), which were also supported by gene structures and conserved motifs analysis. Group II contained only two CsSABATH proteins, which were closely related to PtIAMT, AtIAMT and OsIAMT. The group III SABATH genes of tea plant exhibited expansion on the CSS genome compared with Camellia sinensis var. assamica (CSA) genome. Based on RNA-seq data, the CsSABATHs exhibited tissue-specific expression patterns, and the members with high expression in buds and young leaves were also obviously upregulated after MeJA treatment. The expression of many transcription factors was significantly correlated with that of different members of the CsSABATH gene family, suggesting a potential regulatory relationship between them. Quantitative real-time PCR (qPCR) expression analysis showed that CsSABATHs could respond to exogenous JA, SA and MeSA treatments in tea plants. RNA-seq data analysis and qPCR validation suggested that CsSABATH8 , 11, 16, 25, 29 and 32 might play a special role in plant defense against insect herbivory. These results provide references for evolutionary studies of the plant SABATH family and the exploration of the potential roles of CsSABATHs in tea plant defense responses.

Roots grow asymmetrically, sometimes helically, around their growth direction likely to facilitate environmental sensing. We recently demonstrated that nitrate deficiency induces root coiling on horizontal surface through nitrate transporter/sensor NRT1.1 and PIN2- and AUX-mediated polar auxin transport. Here, we show that nitrate deficiency or NRT1.1 loss-of-function induces differential distribution of PIN2 between the future concave and concave sides in root epidermal cells. Treatment with pharmacological drugs suggests that enhanced endocytosis at the future convex side leads to reduced plasma membrane (PM) association of PIN2. A reduction of PIN2 at the PM would maintain a low auxin response to further enhance endocytosis at the convex side, leading to root coiling.

CAPRICE (CPC), an R3-type MYB transcription factor, is known to promote root hair differentiation in the root epidermis of Arabidopsis . CPC moves from non-hair cells to adjacent hair-forming cells. In contrast, we have previously shown that there is no movement of the CPC homologs, ENHANCER OF TRY AND CPC 1, 2, and 3 (ETC1, 2, and 3), and TRYPTICHON (TRY) between root epidermal cells. We also identified a tomato homolog of CPC , named Solanum lycopersicumTRYPTICHON ( SlTRY ). SlTRY -introduced transgenic Arabidopsis produced many root hairs, like CPC -introduced transgenic Arabidopsis . To clarify the cell-to-cell movement ability of the SlTRY protein, in this study, we observed the distribution of GFP fluorescence in CPCp:SlTRY:GFP transgenic Arabidopsis . Unexpectedly, SlTRY moved from non-hair cells to adjacent root hair cells, like CPC, in Arabidopsis root epidermis. SlTRY does not have the cell-to-cell movement sequence (S1) defined in CPC, and the mechanism of movement is still unknown. Further investigation is necessary to elucidate the mechanism of cell-to-cell movement of SlTRY. Our results will help in the further unraveling of the functions of these MYB transcription factors in determining cell fate.

Strigolactone and karrikin receptors, DWARF14 (D14) and KARRIKIN INSENSITIVE 2 (KAI2), respectively, have been shown to positively regulate drought resistance in Arabidopsis thaliana by modulating abscisic acid responsiveness, anthocyanin accumulation, stomatal closure, cell membrane integrity and cuticle formation. Here, we aim to identify genes specifically or commonly regulated by D14 and KAI2 under water scarcity, using comparative analysis of the transcriptome data of the A. thaliana d14-1 and kai2-2 mutants under dehydration conditions. In comparison with wild-type, under dehydration conditions, the expression levels of genes related to photosynthesis and the metabolism of glucosinolates and trehalose were significantly changed in both d14-1 and kai2-2 mutant plants, whereas the transcript levels of genes related to the metabolism of cytokinins and brassinosteroids were significantly altered in the d14-1 mutant plants only. These results suggest that cytokinin and brassinosteroid metabolism might be specifically regulated by the D14 pathway, whereas photosynthesis and metabolism of glucosinolates and trehalose are potentially regulated by both D14 and KAI2 pathways in plant response to water scarcity.

The B-box proteins (BBXs) are a family of zinc finger proteins containing one/two B-box domain(s), which play important roles in plant growth and development. Though the Arabidopsis thaliana BBX family genes have been identified and named, no systematic study has taken on BBX family genes involved in the regulation of UV-B induced photomorphogenesis in Arabidopsis thaliana . In our previous report, BBX24/STO was demonstrated to be a negative regulator in UV-B signaling pathway in Arabidopsis . In the present study, the total 32 BBX family genes from Arabidopsis were analyzed, including their structures, conserved domains, phylogenetic relationships, promoter cis-regulatory elements, expression patterns under UV-B radiation. The expression profile of GEO Datasets (GSE117199) related to UV-B in NCBI database was analyzed. qRT-PCR was used to validate the expression profile of several BBX genes in Arabidopsis treated with UV-B. The promoters of AtBBXs contained cis-acting elements that respond to light and hormones, including ethylene, auxin (IAA), abscisic acid (ABA), gibberellin (GA) and methyl jasmonate (MeJA). BBX24 and BBX25 were collinear blocks, suggesting that BBX25 may also be involved in UV-B signal transduction. Expression profile analysis and qRT-PCR validation showed that UV-B induced up-regulation of BBX1, BBX7, BBX20, BBX25 and BBX32 , suggesting that At BBXs were mainly involved in UV-B photomorphogenesis. It is predicted that BBX1, BBX7, BBX20 and BBX25 may be new members in response to UV-B signaling.

For years, ethylene has been known to humankind as the plant hormone responsible for fruit ripening. However, the multitasking aspect of ethylene is still being investigated as ever. It is one of the most diversified signaling molecules which acclimatize plant under adverse conditions. It promotes adventitious root formation, stem and petiole elongation, opening and closing of stomatal aperture, reduces salinity and metal stress, etc. Presence of ethylene checks the production and scavenging of reactive oxygen species by strengthening the antioxidant machinery. Meanwhile, it interacts with other signaling molecules and initiates a cascade of adaptive responses. In the present mini review, the biosynthesis and sources of ethylene production, interaction with other signaling molecules, and its exogenous application under different abiotic stresses have been discussed.

Arbuscular mycorrhiza (AM) is a symbiotic interaction in terrestrial plants that is colonized by fungi in the Glomeromycotina. The morphological types of AM, including the Arum -type and Paris -type, are distinct, depending on the host plant species. A part of the regulatory pathways in Arum -type AM symbiosis has been revealed because most model plants form the Arum -type AM with a model AM fungus, Rhizophagus irregularis . Moreover, gibberellin (GA) is known to severely inhibit AM fungal colonization in Arum -type AM symbiosis. Recently, we showed that exogenous GA treatment significantly promoted AM fungal colonization in Paris -type AM symbiosis in Eustoma grandiflorum . In this study, we focused on the transcriptional changes in AM symbiosis-related genes in GA-treated E. grandiflorum . The expression levels of all examined E. grandiflorum genes were maintained or increased by GA treatment compared with those of the control treatment. Our new results suggest that signaling pathway(s) required for establishing AM symbiosis in E. grandiflorum may be distinct from the well-characterized pathway for that in model plants.

Environmental factors such as photoperiod, temperature, phytohormones, sugars, and soil nutrients can affect the development of axillary meristems and emergence of shoot branches in plants. We investigated how an extended period of cold exposure to Arabidopsis plants before and after inflorescence meristem differentiation would affect plant growth and shoot branching. The number of rosette leaves and shoot branches increased when wild type (WT) juvenile seedlings, but not adult plants, were subjected to a prolonged cold exposure (10/7°C day/night cycle). As the duration of cold exposure to WT juvenile seedlings increased, so too did the rosette area, number of leaves, and rosette branches revealing an extended period of vegetative growth. The prolonged cold treatment also increased the primary inflorescence stem height and number of cauline branches in WT plants revealing a delay in reproductive development that could be altered by early ( set domain group 8; sdg8 ) and late ( methyltransferase 1; met1 ) flowering mutants. The axillary buds/leaf and rosette branches/leaf ratios declined significantly in WT, yet were enhanced in the loss-of-function of carotenoid cleavage dioxygenase 7 ( ccd7 ) and teosinte branched 1 ( brc1 ) hyper-branched mutants. This indicated that axillary meristem differentiation continued during the cold exposure, which did not directly impact axillary bud formation or shoot branching. We conclude that a prolonged cold exposure to juvenile seedlings prior to inflorescence meristem development extended vegetative growth and delayed the reproductive phase to allow additional leaf primordia and axillary meristems to differentiate that enhanced the number of shoot branches in Arabidopsis .

Cell cultures established from various plant species have been used for a range of physiological and biochemical studies. Homogeneity of cell types and size of clusters in the cell culture often gave a clearer and simpler results compared to those obtained with the whole plant. On the other hand, possible variability of physiological conditions and responsiveness to external stimuli between the cell lines could be problematic for comparative studies. Aiming at combining the usefulness of plant cell culture with the rich information and genetic resources of Arabidopsis, we systemically examined the methods/conditions to establish cell lines for comparative studies, which could be applicable to a variety of genetic resources. Arabidopsis cell lines thus established from the meristem of mature seeds showed reproducible and comparable MAMP responses such as ROS generation and defense-related gene expression. MAMP responses of the cultured cells showed the specificity depending on the presence/absence of the corresponding MAMP receptor. Pharmacological study with a protein kinase inhibitor, K252a, also showed the usefulness of the cell culture for such studies. These results indicated the usefulness of the method to establish Arabidopsis cell lines, which are useful for comparative studies between genetic resources.

As stress-inducible proteins, dehydrins exert functional protective role by alleviating the cell damage when plants are suffering from the stresses. However, the upstream regulatory mechanism of these proteins is not very clear. To unravel the regulatory mechanism of dehydrin, a screen of wheat cDNA library from cold and PEG-treated wheat seedlings was performed and a transcription factor TaERF4a (GenBank NO. AFP49822.1) interacting with wheat dehydrin wzy1-2 gene (Gene ID: 100037544) promoter was identified by yeast one-hybrid assay. The regulator TaERF4a and the wzy1-2 gene can respond to the abiotic stress, the induced transcripts of these two genes exhibit a similar expression trend under adverse environmental conditions. In planta, the dual luciferase transient assay analysis showed that TaERF4a can positively regulate the expression of WZY1-2 dehydrin. Therefore, the obtained results suggest that ERF transcription factor can regulate the expression level of the dehydrin gene in wheat.

An ability of plants memorizing past heat exposure to modulate the expression of stress response transcripts during recovery is essential for efficient acquired thermotolerance. In this study, we demonstrated that expression of heat response transcripts spiked at 30 min or 1 h, but dramatically declined at 3 h during recoveries following exposure to 5-min heat stress in Arabidopsis. In contrast, expression of transcripts up-regulated by 45-min heat stress was sustained for 30 min or 1 h then declined during recovery. These results suggest that heat memory can be differently modulated depending on the duration of heat exposure, and indicate that plants can memorize even 5-min heat stress to regulate acclimatory responses during recovery. Later hypothesis can be supported by the finding that accumulation of heat response proteins was also modulated during recovery following 5-min heat stress. In addition, 5-min heat stress followed by 3 h recovery was efficient to activate acquired thermotolerance of plants, although spike of transcript expression was observed at 1 h during recovery. These results suggest that plants possess the ability to quickly memorize heat stress and reset cellular states during recovery to adapt to subsequent severe heat stress.

The signaling network formed by external environmental signals and endogenous hormone signals is an important basis for the adaptive growth of plants. We recently identified a UDP-glucosyltransferase gene, UGT76F1 , which controls the glucosylation of auxin precursor IPyA and mediates light-temperature signaling to regulate auxin-dependent hypocotyl elongation in Arabidopsis. However, it is unclear whether UGT76F1 is involved in the adaptive growth of other tissues and whether it is related to the signaling of other hormones besides auxin. Here we investigated the petiole elongation of UGT76F1 overexpression lines and knockout mutant lines, and also studied the effects of UGT76F1 on BR signaling. Experimental results indicated that UGT76F1 is involved in the PIF4-mediated petiole growth under high temperature and that UGT76F1 is also related to the BR signaling in controlling hypocotyl growth. These results suggest that UGT76F1 may have a wider significance in the plant adaptations to surrounding environments.

Cytokinin plays crucial roles in regulating plant growth and development, with the signal transduction mediated by type-A and type-B response regulators (RRs).While much genetic knowledge about RRs on regulating plant height remains unclear. Here, we found that overexpressing an OsORR2 gene (a type-B RR) could reduce plant height in rice compared with the wild type (WT). Using quantitative real time (RT-qPCR) assay, OsORR2 was expressed widely in most tissues such as root, culm, sheath, leaf, and panicle. Strong signals were detected in leaf mesophyll cells and anther by in situ hybridization assays (ISH). The subcellular localization of OsORR2 was in cell nucleus. In addition, we found that the transcriptional expression levels of type-A RR genes such as OsRR9, OsRR10, OsRR12 , and OsRR13 were significantly up-regulated in the overexpression transgenic plants (OE) plants. Taken together, our data suggested that OsORR2 was involved in the development of plant height in rice and provided a foundation for future deep molecular research of the type-B RRs.

The C4 plants like maize are at an advantage because they exhibit higher carbon conversion efficiency than C3 during photosynthesis. Using the evaluation of photosynthetic phenotypes and subcellular structure, and high-quality transcriptome analysis for four types of leaves from a bundle sheath defective maize mutant ( bsd ) and 501 wild line, the key target genes, important transcription factors, and specific pathways were obtained, which may regulate the C-concentrating mechanisms and antioxidant protection of the photosynthetic system, gibberellin signaling, ribosome editing, glycolysis, and chlorophyll biosynthesis. Based on these target genes, a novel network with photosynthetic transformation efficiency with oxidative decarboxylation and ribosome regulation was filtered innovatively by Cytoscape, which adds to our understanding for high-efficiency C-fixation and its genetic improvement in C3 and C4 plants.

Histone deacetylases (HDACs) play an important role in plant stress response. In Brachypodium distachyon , which is model species for molecular biology research on monocot plants, the histone deacetylase BdHD1, homologous to AtHDAC1 of the RPD3/HDA1 class, functions as a positive regulator in the plant drought stress response. AtHDAC1 has been found to interact with transcription factors to regulate gene expression. However, the drought-responsive transcription factors that interact with BdHD1 have not been identified yet. Previously, we identified BdWRKY24 and BdMYB22 as drought responsive transcription factors in Brachypodium . In this study, we used yeast two-hybrid (Y2 H) and bimolecular fluorescence complementation (BiFC) assays to show that BdHD1 interacts with BdWRKY24 and BdMYB22. Our findings provides a base to investigate BdHD1-transcription factor complexes in the context of drought stress response in Brachypodium .

Earlier, we reported that Arabidopsis young lateral roots (LR) exhibited improved lethal salinity tolerance as compared with the primary root (PR). We have shown that cell death processes which take place in the PR during salt stress are postponed in the LR. Still, very little is known about the regulation of cell survival mechanisms in the LR during salinity stress. Here we used transgenic Arabidopsis plants expressing Cyclin B1;1:GUS, to further study the responses to salinity in the PR and LR positions. We found strong Cyclin B1;1:GUS activity in young budding LR of salt stressed and stress recovered plants. The Cyclin B1;1:GUS activity dropped significantly in long LR and was almost completely abolished in the PR. Our data provides another line of evidence that position-dependent response occurs in Arabidopsis roots during lethal salinity. The possible roles Cyclin B1;1 plays in the young LR during the response to lethal salinity are discussed.

The transcription factor MYB15 plays an important role in grape basal immunity, and its promoter can be used as a potential target in resistance breeding. However, the regulatory mechanisms of cis -elements in its promoter region under a variety of stresses remain unclear. In this study, we identified some putative cis -regulatory elements present upstream of MYB15 in Vitis quinquangularis Shanyang ( pVqMYB15 _SY) and subsequently characterized the function of these elements using reporter assays. Our results showed that TCA-elements 1 and 2, ABRE, MYC and 3-AF1 binding site 1 are key cis -regulatory elements in pVqMYB15 _SY and play important roles in plant bio/abiotic stress resistance.

The control of gynecium development in Arabidopsis thaliana by the auxin response factor ETTIN (ETT) correlates with a reduction in the methylesterification of cell-wall pectins and a decrease in cell-wall stiffness in the valve tissues of the ovary. Here, we determine the list of genes rapidly regulated following the in-vivo activation of an ETT fusion protein, and show these to be significantly enriched in genes encoding cell-wall proteins, including several pectin methylesterases (PMEs) and pectin methylesterase inhibitors (PMEIs). We also perform a genome-wide scan for potential ETT-binding sites, and incorporate the results of this procedure into a comparison of datasets, derived using four distinct methods, to identify genes regulated directly or indirectly by ETT. We conclude from our combined analyses that PMEIs are likely to be key actors that mediate the regulation of gynecium development by ETT, while ETT may simultaneously regulate PMEs to prevent exaggerated developmental effects from the regulation of PMEIs. We also postulate the existence of one or more rapidly-acting intermediate factors in the transcriptional regulation of PMEs and PMEIs by ETT.

In our recent publication, we have shown that a member of the Laccase family, LACCASE2 ( LAC2) acted as a negative regulator of lignin deposition in the root xylem tissue of Arabidopsis thaliana. LAC2 messenger RNA (mRNA) level was post-transcriptionally regulated by microRNA 397b, which showed increased expression under water and phosphate deficiency, resulting in the downregulation of LAC2 expression In this report, we have investigated root growth and lignin deposition in an economically important legume crop chickpea ( Cicer arietinum L.) in response to natural drought in soil-grown condition. In contrast to the growth retardation of Arabidopsis root in mannitol-supplemented medium, chickpea root showed an increase in length in low soil moisture condition. Lignin estimation in the primary root showed an increase in lignin content, which was substantiated by staining of root xylem. Drought treatment enhanced the expression of four out of six LAC genes tested, while the expression of two was downregulated. Our preliminary study indicateed a molecular mechanism of lignin deposition in chickpea root xylem during drought.

Anthocyanins are considered health-promoting phytonutrients; however, anthocyanins strictly occurr in the fruit peel of purple tomato cultivars, making the total anthocyanin content limited per tomato fruit. In this study, we performed a transcriptome analysis between the fruit peel and flesh of a purple tomato cultivar 'Indigo Rose' at both the mature green stage and breaking stage. In total, 1,945 differently expressed genes, including 165 transcription factors, were detected between the fruit peel and flesh, both at and after the mature green stage. We further analyzed the transcription of anthocyanin biosynthesis genes and the regulatory genes composing the MYB-bHLH-WD40 (MBW) complex between the fruit peel and flesh at both development stages. In addition, several light-sensing genes and other transcription factor genes, including BBX family genes and WRKY genes, showed different expression patterns between the fruit peel and flesh. These findings deepen our understanding of anthocyanin biosynthesis in tomato fruit peels and facilitate the identification of genes limiting the anthocyanin biosynthesis in tomato fruit flesh.

As an apoplast signal molecule, extracellular ATP (eATP) is involved in the growth regulation of Arabidopsis thaliana seedlings. Recently, RRFT1 was revealed to be involved in eATP- regulated seedling growth. To further verify the role of RRTF1 in seedlings' eATP response, expression of 20 eATP-responsive genes in wild type (Col-0) and RRTF1 null mutant (rrtf1-1) seedlings were investigated by using realtime quantitative PCR. After 0.5 mM ATP stimulation, the response of these genes' expression in rrtf1-1 seedlings was significantly different from that in Col-0 seedlings. Proteins which are encoded by these genes include transcription factors, plasma membrane receptors like kinases, ion influx/efflux transporters and hormone signaling components. The results indicated that RRTF1 may be involved in eATP regulated physiological responses via regulating the expression of some functional genes.

Calcium (Ca 2+ ) as a universal signal molecule plays pivotal roles in plant growth and development. It regulates root morphogenesis mainly through mediating phytohormone and stress signalings or affecting these signalings. In recent years, much progress has been made in understanding the roles of Ca 2+ in primary root development. Here, we summarize recent advances in the functions and mechanisms of Ca 2+ in modulating primary root growth in plants under normal and stressful conditions.

Seed germination, a crucial developmental step, is regulated by multiple plant endogenous signals, among which phytohormones absisic acid (ABA) and gibberellin (GA) act antagonistically. Reactive oxygen species (ROS) interact with the two hormones to coordinate germination. We have previously reported that Arabidopsis glutamate receptor homolog3.5 (AtGLR3.5) modulates calcium signal to attenuate the repression effect of ABA on seed germination and that amino acid L-methionine functions upstream of AtGLR3.5, resulting in calcium influx. Here, we show that AtGLR3.5 modulates GA and ROS signaling during seed germination. Our findings provide a more complete picture as to the molecular mechanisms of AtGLR3.5 in seed germination control.

Apoplastic barriers in the endodermis, such as Casparian strips and suberin lamellae, control the passage of water and minerals into the stele. Apoplastic barriers are thus thought to contribute to salt exclusion in salt-excluding plants such as sweet sorghum ( Sorghum bicolor ). However, little is known about the genes involved in the development of the apoplastic barrier. Here, we identified candidate genes involved in Casparian strip and suberin lamella development in the roots of a sweet sorghum line (M-81E). Three distinct developmental regions (no differentiation, developing, and mature) were identified based on Casparian strip and suberin lamella staining in root cross sections. Sequencing of RNA extracted from these distinct sections identified key genes participating in the differentiation of the apoplastic barrier. The different sections were structurally distinct, presumably due to differences in gene expression. Genes controlling the phenylpropanoid pathway, fatty acid elongation, and fatty acid ω-hydroxylation appeared to be directly responsible for the formation of the apoplastic barrier. Our dataset elucidates the molecular processes underpinning apoplastic barrier development and provides a basis for future research on molecular mechanisms of apoplastic barrier formation and salt exclusion. Abbreviations: SHR, SHORTROOT; MYB, MYB DOMAIN PROTEIN; CIFs, Casparian strip integrity factors; CASP, Casparian strip domain proteins; PER, peroxidase; ESB1, ENHANCED SUBERIN1; CS, Casparian strip; RPKM, reads per kilobase per million reads; DEGs, differentially expressed genes; FDR, false discovery rate; GO, Gene Ontology; KEGG, Kyoto Encyclopedia of Genes and Genomes; RNA-seq, RNA sequencing; PAL, phenylalanine ammonia-lyase; CYP, cytochrome P450 monooxygenases; 4CL, 4-coumarate-CoA ligase; AAE5, ACYL-ACTIVATING ENZYME5; CCR, cinnamoyl CoA reductase; TKPR, TETRAKETIDE ALPHA-PYRONE REDUCTASE1; CAD, cinnamyl alcohol dehydrogenase; HST, shikimate O -hydroxycinnamoyltransferase; PMAT2, PHENOLIC GLUCOSIDE MALONYLTRANSFERASE2; CCOAOMT, caffeoyl-CoA O -methyltransferase; KCS, β-ketoacyl-CoA synthase; CUT1, CUTICULAR PROTEIN1; DET2, 5-alpha-reductase; TAX, 3'- N -debenzoyl-2'-deoxytaxol N -benzoyltransferase; CER1, ECERIFERUM1; FAR, fatty acyl reductase; AF-CoA, alcohol-forming fatty acyl-CoA reductase; ABCG, ATP-binding cassette, subfamily G; ERF, ethylene-responsive transcription factor; HSF, heat stress transcription factor; NTF, NUCLEAR TRANSCRIPTION FACTOR Y SUBUNIT B-5; GPAT, glycerol 3-phosphate acyltransferase.

Phytochrome A (phyA) is the primary photoreceptor mediating various plant responses to far-red (FR) light. The defense-related phytohorme jasmonic acid (JA) has been shown recently to play a role in regulating phyA-mediated FR signaling. However, the detailed molecular mechanisms governing phyA- and JA-mediated signaling cross talks are still not well understood. Here, we uncover a molecular cascade in which JAZ1 inactivates phyA signaling through repressing the transcriptional activity of FHY3 on FHY1 and FHL . Furthermore, we demonstrate that the expression levels of FHY1 and FHL , and some FR response genes are reduced in the coi1 mutant. These findings unveil a previously unrecognized mechanism whereby JA modulates phyA signaling through repressing the activities of FHY3 by JAZs.

Stomata not only control the important balance between gaseous fluxes and water loss, but also act as a route of invading pathogen entry into the plant. Here, the stomatal opening was observed to be induced by a necrotrophic pathogen Sclerotinia sclerotiorum at the early stages of infection. In contrast to uninfected control, the stomatal pores were still opened in S. sclerotiorum -infected regions after dark adaption. Mutation of violaxanthin de-epoxidase, a key enzyme in the xanthophyll cycle, could partially restore the S. sclerotiorum -induced stomatal opening. Further studies showed that S. sclerotiorum invasion led to a decrease in electron transport rate, but a significant increase in non-photochemical quenching (NPQ). The decay kinetics of NPQ revealed that zeaxanthin epoxidase (ZEP, also known as ABA1) was continuous deactivation in S. sclerotiorum -infected region. HPLC-MS/MS analysis showed a slight increase of jasmonate acid (JA), but a great decrease of abscisic acid (ABA) content in S. sclerotiorum -inoculated tissue. Exogenous application of ABA but not JA could rescue the abnormal stomatal opening. Together, these results suggested that the S. sclerotiorum -induced decrease of ABA biosynthesis reduced stomatal closing via dysfunction of the xanthophyll cycle during early pathogenesis.

OsCASP1 (Casparian strip domain protein 1) was recently identified to function in Casparian strip (CS) formation at the endodermal cells in rice roots, which was required for selective mineral uptake in rice. Here, we further investigate the functional form of OsCASP1 in vivo . Expression analysis shows that OsCASP1, OsCASP2, OsCASP3 , and OsCASP5 were expressed in roots apart from OsCASP4 . A yeast two-hybrid (Y2H) assay revealed that OsCASP1 can interact with itself and OsCASP2, but not with OsCASP3 and OsCASP5. These interactions of OsCASP1 with itself and OsCASP2 at the plasma membrane were confirmed using bimolecular fluorescence complementation (BiFC) in rice protoplasts. These results indicated that OsCASP1 can form complexes with itself and OsCASP2 in rice roots.

By timing many diel rhythmic events, circadian clock provides an adaptive advantage for higher plants. Meanwhile, circadian clock displays plasticity and can be entrained by the external environmental cues and internal factors. However, whether cellular energy status can regulate circadian clock is largely unknown in higher plants. The evolutionarily conserved TOR (target of rapamycin) signaling among eukaryotic organisms has been implicated as an integrator for cellular nutrient and energy status. Here, we demonstrated that chemically blocking electron transport chain of mitochondrial can lengthen the circadian period. Similarly, chemical inhibition of TOR activity by Torin 1, a specific inhibitor for TOR kinase, and knockdown of TOR transcript levels significantly elongate the circadian period as well. Our findings imply that TOR signaling may mediate energy status-regulated circadian clock in plants, and the reciprocal regulation between the circadian clock and TOR signaling might be an evolutionary mechanism for fitness and adaptation in plants.

The plant hormone ethylene is a key regulator of growth, development and stress adaptation at all stages of the plant life cycle. Signal perception and response to the plant hormone are mediated by a family of receptor kinases localized at the ER-Golgi network which gain their high affinity and specificity for the chemically simple ethylene molecule by an essential copper cofactor bound at their transmembrane domain. Transfer of this cofactor from the plant plasma membrane to the ER-localized receptors requires secured cellular transport of the reactive transition metal. In a recent study, we disclosed the transport proteins involved in the copper transfer to the receptors and identified that cytoplasmic chaperones of the ATX1-family and a membrane-bound P -type ATPase are involved in copper routing. Strictly speaking, our data show that receptors can acquire their copper load by different routes and adopt the metal ion from the plasma membrane either by sequential transfer from soluble chaperones of the ATX1-family via the ER-bound copper-transporting ATPase RAN1 or by direct transfer from the soluble chaperones. Here, we have studied the properties of the soluble plant copper chaperone isoforms, ATX1 and CCH, in more detail. Our data support different cellular functions of these isoforms on copper mobilization.

Most primary auxin response genes are classified into three families, namely AUX/IAAs, GH3 s, and SAURs . As a rapidly developing field of plant biology, recent studies have begun to address the function and mechanism of plant SAURs . We found that, in Arabidopsis, the SAUR41 subfamily genes were ABA-inducible, and overexpression of SAUR41 induced the biosynthesis of ABA. The saur41/40/71/72 quadruple mutants and the SAUR41 overexpression lines had an altered expression of ABA and calcium homeostasis/signaling genes, but not the AUX/IAAs and GH3s . Here, we reported that the quadruple mutants showed an increased sensitivity to ABA treatment, in terms of cotyledon greening/expansion rate, while for the overexpression lines, this was decreased. With respect to the root touch response, the overexpression of SAUR41 led to an extensive root looping phenotype, while the quadruple mutations of saur41s led to a relaxed root looping. As reported, the ion content (Na + , K + and Fe 2+ ), apoplast acidification ability, and salt tolerance were also abnormal in the quadruple mutants and/or the SAUR41 overexpression lines. Our work supports an emerging concept that ABA and calcium are integrated together to modulate ion homeostasis. In addition, our work demonstrates that SAUR41s might be new components for the regulation of ion homeostasis by ABA and calcium.

VirE2-INTERACTING PROTEIN1 (VIP1) is a basic leucine zipper protein in Arabidopsis thaliana . VIP1 changes its subcellular localization from the cytoplasm to the nucleus when cells are exposed to mechanical or hypo-osmotic stress. The nuclear localization of VIP1 is inhibited either by inhibitors of calcium signaling or by inhibitors of protein phosphatases 1, 2A and 4 (PP1, PP2A and PP4, respectively). VIP1 binds to the PP2A B"-family subunits, which have calcium-binding EF-hand motifs and which act as the regulatory, substrate-recruiting B subunit of PP2A. The VIP1 de-phosphorylation can therefore be mediated by PP2A. However, details of the PP2A-mediated de-phosphorylation of VIP1 are unclear. Here, with yeast two-hybrid assays and in-vitro pull-down assays, we show that VIP1 does not interact with the scaffolding A subunit of PP2A, but that VIP1 does interact with the catalytic C subunits. Our data raise the possibility that not only the B"-family B subunit of PP2A but also its C subunit contributes to the PP2A-mediated de-phosphorylation of VIP1.

Crop productivity depends heavily on several biotic and abiotic factors. Plant annexins are a multigene family of calcium-dependent phospholipid-binding proteins that function in response to environmental stresses and signaling during growth and development of plants. We recently isolated and characterized a Triticum durum annexin, called TdANN12 , which is upregulated by different abiotic stresses. Overexpression of TdANN12 in transgenic tobacco improves stress tolerance through ROS removal. This mini-review outlines the functional characterization of plant annexin genes and suggests how these features could be exploitated to improve stress tolerance in plants. Furthermore, transgenic overexpression of plant annexin genes in crops (tobacco, tomato, rice, alfalfa, cotton, and potato) will be discussed as a promising approach to acquire abiotic and biotic stress tolerance.

We recently reported the transcriptomic signature of salicylic acid (SA) and jasmonic acid (JA) biosynthetic and responsive genes in Arabidopsis thaliana plants infested with the herbivore Eurydema oleracea . We demonstrated that insect feeding causes induction of both SA- and JA-mediated signaling pathways. Using transgenic SA-deficient NahG plants, we also showed antagonistic cross-talk between these two phytohormones. To gain more insight into the roles of the SA and JA pathways in plant defenses against E. oleracea , we report here on the dynamics of SA and JA levels in the wild-type genotype Col-0 and the transgenic Arabidopsis NahG mutant that does not accumulate SA. We show that SA strongly accumulates in the wild-type plants after 24 h of herbivore infestation, while JA levels do not change significantly. On the contrary, in the infested NahG plants, SA levels were not affected by E. oleracea feeding, whereas JA levels which were constitutively higher than the wild-type did not significantly change after 6 hours of herbivore feeding. Accordingly, when the wild-type and the jar1-1 mutant (which fails to accumulate JA-Ile) Arabidopsis plants were challenged with E. oleracea in a two-choice arena, the insect fed preferentially on the jar1-1 plants over the wild-type. These data support the conclusion that E. oleracea infestation strongly induces the SA pathway in the wild-type, thus antagonizing JA-mediated plant defenses against herbivory, as a strategy to suppress plant immunity.

Oligosaccharins, which are biologically active oligosaccharide fragments of cell wall polysaccharides, may regulate the processes of growth and development as well as the response to stress factors. We characterized the effect of the oligosaccharin that stimulates rhizogenesis (OSRG) on the gene expression profile in the course of IAA-induced formation of adventitious roots in hypocotyl explants of buckwheat ( Fagopyrum esculentum Moench.). The transcriptomes at two stages of IAA-induced root primordium formation (6 h and 24 h after induction) were compared after either treatment with auxin alone or joint treatment with auxin and OSRG. The set of differentially expressed genes indicated the special importance of oligosaccharin at the early stage of auxin-induced adventitious root formation. The list of genes with altered mRNA abundance in the presence of oligosaccharin included those, which Arabidopsis homologs encode proteins directly involved in the response to auxin as well as proteins that contribute to redox regulation, detoxification of various compounds, vesicle trafficking, and cell wall modification. The obtained results contribute to understanding the mechanism of adventitious root formation and demonstrate that OSRG is involved in fine-tuning of ROS and auxin regulatory modes involved in root development.

The plant hormone gibberellin (GA) stimulates developmental transitions including seed germination, flowering, and the transition from juvenile to adult growth stage. This study provided evidence that GA and the GA receptor GID1 ( GA-INSENSITIVE DWARF1 ) are also needed for the embryo-to-seedling transition in Arabidopsis. The ga1-3  GA biosynthesis mutant fails to germinate unless GA is applied, whereas the gid1abc triple mutant fails to germinate because it cannot perceive endogenous or applied GA. Overexpression of the GID1a, GID1b , and GID1c GA receptors rescued the germination of a small percentage of ga1-3 seeds without GA application, and this rescue was improved by dormancy-breaking treatments, after-ripening and cold stratification. While GID1 overexpression stimulated ga1-3 seed germination, this germination was aberrant suggesting incomplete rescue of the germination process. Cotyledons emerged before the radicle, and the resulting "ghost" seedlings failed to develop a primary root, lost green coloration, and eventually died. The development of ga1-3 seedlings overexpressing GID1 was rescued by pre-germinative but not post-germinative GA application. Since the gid1abc mutant also exhibited a ghost phenotype after germination was rescued by cutting the seed coat, we concluded that both GA and GID1 are needed for the embryo-to-seedling transition prior to emergence from the seed coat.

Analyzing high-resolution images to gain insight into anatomical properties is an essential tool for investigation in many scientific fields. In plant biology, studying plant phenotypes from micrographs is often used to build hypotheses on gene function. In this report, we discuss a bespoke method for inspecting the significance in the differences between the morphologies of several plant mutants at cellular level. By examining a specific example in the literature, we will detail the approach previously used to quantify the effects of two gene families on the vascular development of hypocotyls in Arabidopsis thaliana . The method incorporates a MATLAB algorithm and statistical tools which can be modified and enhanced to tailor to different research questions in future studies.

Brassinosteroids (BRs) are known to be endogenous regulators of ethylene production, suggesting that some BR activity in plant growth and development is associated with ethylene. Here, we demonstrated that ethylene production in Arabidopsis thaliana roots is increased by BR signaling via the ethylene biosynthetic gene for ACC oxidase 1 ( ACO1 ). Electrophoretic mobility shift and chromatin immune-precipitation assays showed that the BR transcription factor BES1 directly binds to two E-box sequences located in the intergenic region of ACO1 . GUS expression using site mutations of the E-box sequences verified that ACO1 is normally expressed only when BES1 binds to the E-boxes in the putative promoter of ACO1 , indicating that this binding is essential for ACO1 expression and the subsequent production of ethylene in A. thaliana roots. BR exogenously applied to A. thaliana roots enhanced the gravitropic response. Additionally, bes1-D exhibited a greater gravitropic response than did the wild-type specimens, proving that BR is a positive regulator of the gravitropic response in A. thaliana roots. The knock-down mutant aco1-1 showed a slightly lower gravitropic response than did the wild-type specimens, while bes1-D X aco1-1 exhibited a lower gravitropic response than did bes1-D. Therefore, ACO1 is a direct downstream target for BR transcription factor BES1, which controls ethylene production for gravitropism in A. thaliana roots.