ABRE-binding Factor Research Articles

Development and drought escape response in Arabidopsis thaliana are regulated by AtPLC1 in response to abscisic acid.

AtPLC1 plays a critical role in plant growth, development, and response to drought stress. Phosphoinositide-specific phospholipase C (PI-PLC) hydrolyzes substrates to generate secondary messengers crucial for plant growth, development, and stress responses. Drought escape (DE) response is an adaptive strategy that plants employ under drought conditions. The expression levels of the flower meristem-specific gene APETALA 1 and flowering regulatory genes FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 were downregulated in plc1, and FLOWERING LOCUS C was upregulated. The flowering time of the plc1flc double mutant was earlier than that of the wild type. Transcriptome analysis revealed that the Gene Ontology of differentially expressed genes (DEGs) was enriched in abscisic acid (ABA) response signaling, and Kyoto Encyclopedia of Genes and Genomes analysis revealed differential gene expression annotated to plant hormone signaling pathways. Our experiments show that AtPLC1 is upregulated by ABA in Arabidopsis. Under ABA induction and water stress, wild-type plants exhibit a DE response, and the DE response in plc1 disappears. Expression levels of ABA signaling pathway transcription factors ABA-responsive element-binding factors 3 (ABF3) and ABF4 were downregulated in plc1. In conclusion, our study suggests that AtPLC1 participates in regulating plant growth and development and participates in the DE response through the regulation of ABA signaling pathway transcription factors ABF3/ABF4. The study enhances our comprehension of the role of AtPLC1 in plant development and drought stress, providing a theoretical foundation for further investigation into DE responses.

Genome-Wide Analysis of the Phospholipase Ds in Perennial Ryegrass Highlights LpABFs-LpPLDδ3 Cascade Modulated Osmotic and Heat Stress Responses.

The phospholipase Ds (PLDs) are crucial for cellular signalling and play roles in plant abiotic stress response. In this study, we identified 12 PLD genes from the genome data of perennial ryegrass (Lolium perenne), which is widely used as forage and turfgrass. Among them, LpPLDδ3 was significantly repressed by ABA treatment, and induced by drought stress and heat stress treatments. The ectopic overexpression (OE) of LpPLDδ3 in Arabidopsis enhanced plant tolerance to osmotic and heat stress as demonstrated by an increased survival rate and reduced malondialdehyde (MDA) accumulation and electrolyte leakage (EL). Arabidopsis endogenous ABA RESPONSIVE ELEMENT BINDING FACTORs (ABFs) and heat stress responsive genes were elevated in LpPLDδ3 OE lines under osmotic and heat stress treatments. Additionally, overexpression of LpPLDδ3 in perennial ryegrass protoplasts could increase heat stress tolerance and elevate expression level of heat stress responsive genes. Moreover, LpABF2 and LpABF4 depressed the LpPLDδ3 expression by directly binding to its ABRE core-binding motif of promoter region. In summary, LpPLDδ3 was repressed by LpABF2 and LpABF4 and positively involved in perennial ryegrass osmotic and heat stress responses.

Transcriptome analysis suggested that lncRNAs regulate rapeseed seedlings in responding to drought stress by coordinating the phytohormone signal transduction pathways

The growth, yield, and seed quality of rapeseed are negatively affected by drought stress. Therefore, it is of great value to understand the molecular mechanism behind this phenomenon. In a previous study, long non-coding RNAs (lncRNAs) were found to play a key role in the response of rapeseed seedlings to drought stress. However, many questions remained unanswered. This study was the first to investigate the expression profile of lncRNAs not only under control and drought treatment, but also under the rehydration treatment. A total of 381 differentially expressed lncRNA and 10,253 differentially expressed mRNAs were identified in the comparison between drought stress and control condition. In the transition from drought stress to rehydration, 477 differentially expressed lncRNAs and 12,543 differentially expressed mRNAs were detected. After identifying the differentially expressed (DE) lncRNAs, the comprehensive lncRNAs-engaged network with the co-expressed mRNAs in leaves under control, drought and rehydration was investigated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of co-expressed mRNAs identified the most significant pathways related with plant hormones (expecially abscisic acid, auxin, cytokinins, and gibberellins) in the signal transduction. The genes, co-expressed with the most-enriched DE-lncRNAs, were considered as the most effective candidates in the water-loss and water-recovery processes, including protein phosphatase 2 C (PP2C), ABRE-binding factors (ABFs), and SMALL AUXIN UP-REGULATED RNAs (SAURs). In summary, these analyses clearly demonstrated that DE-lncRNAs can act as a regulatory hub in plant-water interaction by controlling phytohormone signaling pathways and provided an alternative way to explore the complex mechanisms of drought tolerance in rapeseed.

Melatonin mitigates drought stress by increasing sucrose synthesis and suppressing abscisic acid biosynthesis in tomato seedlings.

The increasing prevalence of drought events poses a major challenge for upcoming crop production. Melatonin is a tiny indolic tonic substance with fascinating regulatory functions in plants. While plants can respond in several ways to alleviate drought stress, the processes underpinning stress sensing and signaling are poorly understood. Hereafter, the objectives of this investigation were to explore the putative functions of melatonin in the regulation of sugar metabolism and abscisic acid biosynthesis in drought-stressed tomato seedlings. Melatonin (100 μM) and/or water were foliar sprayed, followed by the plants being imposed to drought stress for 14 days. Drought stress significantly decreased biomass accumulation, inhibited photosynthetic activity, and stimulated senescence-associated gene 12 (SAG12) expression. Melatonin treatment effectively reversed drought-induced growth retardation as evidenced by increased leaf pigment and water balance and restricted abscisic acid (ABA) accumulation. Sugar accumulation, particularly sucrose content, was higher in drought-imposed seedlings, possibly owing to higher transcription levels of sucrose non-fermenting 1-related protein kinase 2 (SnKR2.2) and ABA-responsive element binding factors 2 (AREB2). Melatonin addition further uplifted the sucrose content, which coincided with increased activity of sucrose synthase (SS, 130%), sucrose phosphate synthase (SPS, 137%), starch degradation encoding enzyme β-amylase (BAM, 40%) and α-amylase (AMY, 59%) activity and upregulated their encoding BAM1(10.3 folds) and AMY3 (8.1 folds) genes expression at day 14 relative to the control. Under water deficit conditions, melatonin supplementation decreased the ABA content (24%) and its biosynthesis gene expressions. Additionally, sugar transporter subfamily genes SUT1 and SUT4 expression were upregulated by the addition of melatonin. Collectively, our findings illustrate that melatonin enhances drought tolerance in tomato seedlings by stimulating sugar metabolism and negatively regulating ABA synthesis.

Genome-wide analysis of ABF gene family in lettuce (Lactuca sativa L.) reveals the negative roles of LsABF1 in thermally induced bolting

ABSTRACT High-temperature-induced early bolting poses a pressing challenge in annual leaf lettuce cultivation. ABF transcription factors, or ABA-responsive element binding factors, are crucial components of the ABA signalling pathway. In this study, we identified 8 members of the ABF gene family in leaf lettuce, categorising them into groups A, B, and C through phylogenetic analysis. All LsABFs exhibited a conserved domain, RMIKNRESAARSRARKQAY (Bzip_plant_BZIP46), as revealed by multiple sequence alignment. A total of 1242 cis-acting elements were detected, with 323 elements screened. Predictive analysis indicated 304 phosphorylation sites. Expression patterns of LsABFs were similar, peaking on the 8th day, implicating their role in bolting. Silencing LsABF1 positively impacted lettuce bolting, signifying its regulatory potential. This study establishes a theoretical foundation for comprehending the molecular mechanisms governing ABF genes in high-temperature-induced bolting in leaf lettuce.

Essential role of ABA signaling and related transcription factors in phenolic acid and lignin synthesis during muskmelon wound healing.

Abscisic acid (ABA) is a key phytohormone involved in wound healing in fruits and vegetables, while fluridone (FLD) is its synthetic inhibitor. However, it is unknown whether ABA signaling and downstream transcription factors are involved in the synthesis of phenolic acids and lignin monomers in muskmelon wounds, and the underlying mechanisms. In our study, exogenous ABA promoted endogenous ABA synthesis by increasing the levels of β-carotenoid and zeaxanthin, activating 9-cis-epoxycarotenoid dioxygenase (NCED) and zeaxanthin epoxidase (ZEP), facilitated ABA signaling by increasing the expression levels of protein phosphatases type 2C (CmPP2C) and ABA-responsive element binding factors (CmABF), upregulated the expression levels of CmMYB1 and CmWRKY1, and ABA induced phenylpropanoid metabolism by activating phenylalanine ammonia-lyase (PAL), 4-coenzyme A ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD), which further increased the synthesis of phenolic acids and lignin monomers in muskmelon wounds during healing. Taken together, exogenous ABA induced phenylpropanoid metabolism and increased the synthesis of phenolic acid and lignin monomer in muskmelon wounds during healing, and may be involved in endogenous ABA synthesis and signaling and related transcription factors.

PSEUDO-RESPONSE REGULATOR 3b and transcription factor ABF3 modulate abscisic acid-dependent drought stress response in soybean.

The circadian system plays a pivotal role in facilitating the ability of crop plants to respond and adapt to fluctuations in their immediate environment effectively. Despite the increasing comprehension of PSEUDO-RESPONSE REGULATORs and their involvement in the regulation of diverse biological processes, including circadian rhythms, photoperiodic control of flowering, and responses to abiotic stress, the transcriptional networks associated with these factors in soybean (Glycine max (L.) Merr.) remain incompletely characterized. In this study, we provide empirical evidence highlighting the significance of GmPRR3b as a crucial mediator in regulating the circadian clock, drought stress response, and abscisic acid (ABA) signaling pathway in soybeans. A comprehensive analysis of DNA affinity purification sequencing and transcriptome data identified 795 putative target genes directly regulated by GmPRR3b. Among them, a total of 570 exhibited a significant correlation with the response to drought, and eight genes were involved in both the biosynthesis and signaling pathways of ABA. Notably, GmPRR3b played a pivotal role in the negative regulation of the drought response in soybeans by suppressing the expression of abscisic acid-responsive element-binding factor 3 (GmABF3). Additionally, the overexpression of GmABF3 exhibited an increased ability to tolerate drought conditions, and it also restored the hypersensitive phenotype of the GmPRR3b overexpressor. Consistently, studies on the manipulation of GmPRR3b gene expression and genome editing in plants revealed contrasting reactions to drought stress. The findings of our study collectively provide compelling evidence that emphasizes the significant contribution of the GmPRR3b-GmABF3 module in enhancing drought tolerance in soybean plants. Moreover, the transcriptional network of GmPRR3b provides valuable insights into the intricate interactions between this gene and the fundamental biological processes associated with plant adaptation to diverse environmental conditions.

BnaABF3 and BnaMYB44 regulate the transcription of zeaxanthin epoxidase genes in carotenoid and abscisic acid biosynthesis.

Zeaxanthin epoxidase (ZEP) is a key enzyme that catalyzes the conversion of zeaxanthin to violaxanthin in the carotenoid and abscisic acid (ABA) biosynthesis pathways. The rapeseed (Brassica napus) genome has 4 ZEP (BnaZEP) copies that are suspected to have undergone subfunctionalization, yet the 4 genes' underlying regulatory mechanisms remain unknown. Here, we genetically confirmed the functional divergence of the gene pairs BnaA09.ZEP/BnaC09.ZEP and BnaA07.ZEP/BnaC07.ZEP, which encode enzymes with tissue-specific roles in carotenoid and ABA biosynthesis in flowers and leaves, respectively. Molecular and transgenic experiments demonstrated that each BnaZEP pair is transcriptionally regulated via ABA-responsive element-binding factor 3 s (BnaABF3s) and BnaMYB44s as common and specific regulators, respectively. BnaABF3s directly bound to the promoters of all 4 BnaZEPs and activated their transcription, with overexpression of individual BnaABF3s inducing BnaZEP expression and ABA accumulation under drought stress. Conversely, loss of BnaABF3s function resulted in lower expression of several genes functioning in carotenoid and ABA metabolism and compromised drought tolerance. BnaMYB44s specifically targeted and repressed the expression of BnaA09.ZEP/BnaC09.ZEP but not BnaA07.ZEP/BnaC07.ZEP. Overexpression of BnaA07.MYB44 resulted in increased carotenoid content and an altered carotenoid profile in petals. Additionally, RNA-seq analysis indicated that BnaMYB44s functions as a repressor in phenylpropanoid and flavonoid biosynthesis. These findings provide clear evidence for the subfunctionalization of duplicated genes and contribute to our understanding of the complex regulatory network involved in carotenoid and ABA biosynthesis in B. napus.

Physiological and transcriptomic comparisons shed light on the cold stress response mechanisms of Dendrobium spp.

Dendrobium spp. comprise a group of tropical orchids with ornamental and medicinal value. Dendrobium spp. are sensitive to low temperature, and the underlying cold response regulatory mechanisms in this group are unclear. To understand how these plants respond to cold stress, we compared the transcriptomic responses of the cold-tolerant cultivar 'Hongxing' (HX) and the cold-sensitive cultivar 'Sonia Hiasakul' (SH) to cold stress. Chemometric results showed that the physiological response of SH in the later stages of cold stress is similar to that of HX throughout the cold treatment. Orthogonal partial least squares discriminant analysis (OPLS-DA) revealed that soluble protein content and peroxidase activity are key physiological parameters for assessing the cold tolerance of these two Dendrobium spp. cultivars. Additionally, weighted gene co-expression network analysis (WGCNA) results showed that many cold response genes and metabolic pathways significantly associated with the physiological indices were enriched in the 12 detected modules. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene ontology (GO) enrichment analyses of the 105 hub genes showed that Dendrobium spp. adapt to cold stress by regulating signal transduction, phytohormones, transcription factors, protein translation and modification, functional proteins, biosynthesis and metabolism, cell structure, light, and the circadian clock. Hub genes of the cold stress response network included the remorin gene pp34, the abscisic acid signaling pathway-related genes PROTEIN PHOSPATASE 2C (PP2C), SNF1-RELATED PROTEIN KINASE 2 (SnRK2), ABRE-BINDING FACTOR 1 (ABF1) and SKI-INTERACTING PROTEIN 17 (SKIP17), the Ca2+ signaling-related GTP diphosphokinase gene CRSH1, the carbohydrate-related gene STARCH SYNTHASE 2 (SS2), the cell wall biosynthesis gene CINNAMYL ALCOHOL DEHYDROGENASE (CAD7), and the endocytosis-related gene VACUOLAR PROTEIN SORTING-ASSOCIATED PROTEIN 52A (VPS52A). The cold-responsive genes and metabolic pathways of Dendrobium spp. revealed in this study provide important insight to enable the genetic enhancement of cold tolerance in Dendrobium spp., and to facilitate cold tolerance breeding in related plants.

BcABF1 Plays a Role in the Feedback Regulation of Abscisic Acid Signaling via the Direct Activation of BcPYL4 Expression in Pakchoi.

Abscisic acid-responsive element-binding factor 1 (ABF1), a key transcription factor in the ABA signal transduction process, regulates the expression of downstream ABA-responsive genes and is involved in modulating plant responses to abiotic stress and developmental processes. However, there is currently limited research on the feedback regulation of ABF1 in ABA signaling. This study delves into the function of BcABF1 in Pakchoi. We observed a marked increase in BcABF1 expression in leaves upon ABA induction. The overexpression of BcABF1 not only spurred Arabidopsis growth but also augmented the levels of endogenous IAA. Furthermore, BcABF1 overexpression in Arabidopsis significantly decreased leaf water loss and enhanced the expression of genes associated with drought tolerance in the ABA pathway. Intriguingly, we found that BcABF1 can directly activate BcPYL4 expression, a critical receptor in the ABA pathway. Similar to BcABF1, the overexpression of BcPYL4 in Arabidopsis also reduces leaf water loss and promotes the expression of drought and other ABA-responsive genes. Finally, our findings suggested a novel feedback regulation mechanism within the ABA signaling pathway, wherein BcABF1 positively amplifies the ABA signal by directly binding to and activating the BcPYL4 promoter.

Genome-Wide Identification and Expression Profiling of the ABF Transcription Factor Family in Wheat (Triticum aestivum L.).

Members of the abscisic acid (ABA)-responsive element (ABRE) binding factor (ABF) and ABA-responsive element binding protein (AREB) families play essential roles in the regulation of ABA signaling pathway activity and shape the ability of plants to adapt to a range of stressful environmental conditions. To date, however, systematic genome-wide analyses focused on the ABF/AREB gene family in wheat are lacking. Here, we identified 35 ABF/AREB genes in the wheat genome, designated TaABF1-TaABF35 according to their chromosomal distribution. These genes were further classified, based on their phylogenetic relationships, into three groups (A-C), with the TaABF genes in a given group exhibiting similar motifs and similar numbers of introns/exons. Cis-element analyses of the promoter regions upstream of these TaABFs revealed large numbers of ABREs, with the other predominant elements that were identified differing across these three groups. Patterns of TaABF gene expansion were primarily characterized by allopolyploidization and fragment duplication, with purifying selection having played a significant role in the evolution of this gene family. Further expression profiling indicated that the majority of the TaABF genes from groups A and B were highly expressed in various tissues and upregulated following abiotic stress exposure such as drought, low temperature, low nitrogen, etc., while some of the TaABF genes in group C were specifically expressed in grain tissues. Regulatory network analyses revealed that four of the group A TaABFs (TaABF2, TaABF7, TaABF13, and TaABF19) were centrally located in protein-protein interaction networks, with 13 of these TaABF genes being regulated by 11 known miRNAs, which play important roles in abiotic stress resistance such as drought and salt stress. The two primary upstream transcription factor types found to regulate TaABF gene expression were BBR/BPC and ERF, which have previously been reported to be important in the context of plant abiotic stress responses. Together, these results offer insight into the role that the ABF/AREB genes play in the responses of wheat to abiotic stressors, providing a robust foundation for future functional studies of these genes.

Exogenous Abscisic Acid Regulates Anthocyanin Biosynthesis and Gene Expression in Blueberry Leaves

Blueberry (Vaccinium corymbosum) leaves have a positive influence on health because of their phenolic contents, including anthocyanins. Phytohormone abscisic acid (ABA) promotes anthocyanin accumulation, but the underlying mechanisms are unclear in blueberry leaves. In this study, we found that exogenous ABA promotes anthocyanin accumulation in blueberry leaves and we explored the global molecular events involved in these physiological changes by treating in vitro-grown blueberry seedlings with ABA and performing transcriptome deep sequencing (RNA-seq). We identified 6390 differentially expressed genes (DEGs), with 2893 DEGs at 6 h and 4789 at 12 h of ABA treatment compared to the control. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to plant hormone signal transduction and phenylpropanoid and flavonoid biosynthesis were significantly enriched at both stages of the ABA treatment. Analysis of DEGs in plant hormone signal transduction pathways revealed that exogenous ABA affected the expression of genes from other plant hormone signaling pathways, especially brassinosteroid, auxin, and gibberellin signaling. To elucidate the mechanism driving anthocyanin biosynthesis in blueberry in response to ABA treatment, we screened anthocyanin biosynthesis structural genes (ASG) from the phenylpropanoid and flavonoid biosynthetic pathways, MYB transcription factor genes from R2R3-MYB subgroups 5, 6, and 7 and ABRE-binding factor (ABF) genes from the ABA signal transduction pathway. Pearson’s correlation coefficient (r) analysis indicated that the ABFs, MYBs, and structural genes form a network to regulate ABA-induced anthocyanin biosynthesis and MYBA1 is likely to play an important role in this regulatory network. These findings lay the foundation for improving anthocyanin biosynthesis in blueberry leaves.

Comprehensive phytohormone metabolomic and transcriptomic analysis of tobacco (Nicotiana tabacum) infected by tomato spotted wilt virus (TSWV)

Tomato spotted wilt virus (TSWV) is ranked among the top 10 most destructive viruses globally. It results in abnormal leaf growth, stunting, and even death, significantly affecting crop yield and quality. Phytohormones play a crucial role in regulating plant-virus interactions. However, there is still limited research on the effect of TSWV on phytohormone levels, particularly growth hormones and genes involved in the phytohormone pathway. In our study, we combined phytohormone metabolomics and transcriptomics to examine the impact of TSWV infection on phytohormone content and gene expression profile. Metabolomic results showed that 41 metabolites, including major phytohormones and their precursors and derivatives were significantly altered after 14 days of TSWV inoculation tobacco plants cvK326, with 31 being significantly increased and 10 significantly reduced. Specifically, the levels of abscisic acid (ABA) and jasmonoyl-isoleucine (JA-Ile) were significantly reduced. The levels of indole-3-acetic acid (IAA) have remained unchanged. However, the levels of cytokinin isopentenyladenine (iP) and salicylic acid (SA) significantly increased. The transcriptome analysis revealed 2,746 genes with significant changes in expression. Out of these, 1,072 genes were significantly downregulated, while 1,674 genes were significantly upregulated. Among them, genes involved in ABA synthesis and signaling pathways, such as 9-cis-epoxycarotenoid dioxygenase (NCED), protein phosphatase 2C (PP2C), serine/threonine-protein kinase (SnRK2), and abscisic acid responsive element binding factor (ABF), exhibited significant downregulation. Additionally, expression of the lipoxygenase gene LOX, Jasmonate ZIM domain-containing protein gene JAZ, and transcription factor gene MYC were significantly down-regulated. In the cytokinin pathway, while there were no significant changes in the expression of the cytokinin synthesis genes, a significant downregulation of transcriptionally active factor type-B response regulators (type-B RRs) was observed. In terms of SA synthesis and signaling pathways, the isochorismate synthase gene ICS1 and the pathogenesis-related gene PR1 were significantly upregulated. These results can strengthen the theoretical foundation for understanding the interaction between TSWV and tobacco and provide new insights for the future prevention and control of TSWV.

Picea wilsonii NAC31 and DREB2A Cooperatively Activate ERD1 to Modulate Drought Resistance in Transgenic Arabidopsis.

The NAC family of transcription factors (TFs) regulate plant development and abiotic stress. However, the specific function and response mechanism of NAC TFs that increase drought resistance in Picea wilsonii remain largely unknown. In this study, we functionally characterized a member of the PwNAC family known as PwNAC31. PwNAC31 is a nuclear-localized protein with transcriptional activation activity and contains an NAC domain that shows extensive homology with ANAC072 in Arabidopsis. The expression level of PwNAC31 is significantly upregulated under drought and ABA treatments. The heterologous expression of PwNAC31 in atnac072 Arabidopsis mutants enhances the seed vigor and germination rates and restores the hypersensitive phenotype of atnac072 under drought stress, accompanied by the up-regulated expression of drought-responsive genes such as DREB2A (DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN 2A) and ERD1 (EARLY RESPONSIVE TO DEHYDRATION STRESS 1). Yeast two-hybrid and bimolecular fluorescence complementation assays confirmed that PwNAC31 interacts with DREB2A and ABF3 (ABSCISIC ACID-RESPONSIVE ELEMENT-BINDING FACTOR 3). Yeast one-hybrid and dual-luciferase assays showed that PwNAC31, together with its interaction protein DREB2A, directly regulated the expression of ERD1 by binding to the DRE element of the ERD1 promoter. Collectively, our study provides evidence that PwNAC31 activates ERD1 by interacting with DREB2A to enhance drought tolerance in transgenic Arabidopsis.

The positive impact of the NtTAS14-like1 gene on osmotic stress response in Nicotiana tabacum.

NtTAS14-like1 enhances osmotic tolerance through coordinately activating the expression of osmotic- and ABA-related genes. Osmotic stress is one of the most important limiting factors for tobacco (Nicotiana tabacum) growth and development. Dehydrin proteins are widely involved in plant adaptation to osmotic stress, but few of these proteins have been functionally characterized in tobacco. Here, to identify genes required for osmotic stress response in tobacco, an encoding dehydrin protein gene NtTAS14-like1 was isolated based on RNA sequence data. The expression of NtTAS14-like1 was obviously induced by mannitol and abscisic acid (ABA) treatments. Knock down of NtTAS14-like1 expression reduced osmotic tolerance, while overexpression of NtTAS14-like1 conferred tolerance to osmotic stress in transgenic tobacco plants, as determined by physiological analysis of the relative electrolyte leakage and malonaldehyde accumulation. Further expression analysis by quantitative real-time PCR indicated that NtTAS14-like1 participates in osmotic stress response possibly through coordinately activating osmotic- and ABA-related genes expression, such as late embryogenesis abundant (NtLEA5), early responsive to dehydration 10C (NtERD10C), calcium-dependent protein kinase 2 (NtCDPK2), ABA-responsive element-binding protein (NtAREB), ABA-responsive element-binding factor 1 (NtABF1), dehydration-responsive element-binding genes (NtDREB2A), xanthoxin dehydrogenase/reductase (NtABA2), ABA-aldehyde oxidase 3 (NtAAO3), 9-cis-epoxycarotenoid dioxygenase (NtNCED3). Together, this study will facilitate to improve our understandings of molecular and functional properties of plant TAS14 proteins and to improve genetic evidence on the involvement of the NtTAS14-like1 in osmotic stress response of tobacco.

Distinct guard cell-specific remodeling of chromatin accessibility during abscisic acid- and CO2-dependent stomatal regulation.

In plants, epidermal guard cells integrate and respond to numerous environmental signals to control stomatal pore apertures, thereby regulating gas exchange. Chromatin structure controls transcription factor (TF) access to the genome, but whether large-scale chromatin remodeling occurs in guard cells during stomatal movements, and in response to the hormone abscisic acid (ABA) in general, remains unknown. Here, we isolate guard cell nuclei from Arabidopsis thaliana plants to examine whether the physiological signals, ABA and CO2 (carbon dioxide), regulate guard cell chromatin during stomatal movements. Our cell type-specific analyses uncover patterns of chromatin accessibility specific to guard cells and define cis-regulatory sequences supporting guard cell-specific gene expression. We find that ABA triggers extensive and dynamic chromatin remodeling in guard cells, roots, and mesophyll cells with clear patterns of cell type specificity. DNA motif analyses uncover binding sites for distinct TFs enriched in ABA-induced and ABA-repressed chromatin. We identify the Abscisic Acid Response Element (ABRE) Binding Factor (ABF) bZIP-type TFs that are required for ABA-triggered chromatin opening in guard cells and roots and implicate the inhibition of a clade of bHLH-type TFs in controlling ABA-repressed chromatin. Moreover, we demonstrate that ABA and CO2 induce distinct programs of chromatin remodeling, whereby elevated atmospheric CO2 had only minimal impact on chromatin dynamics. We provide insight into the control of guard cell chromatin dynamics and propose that ABA-induced chromatin remodeling primes the genome for abiotic stress resistance.

Exogenous GR24 Inhibits Strawberry Tillering by Affecting the Phytohormone Signaling and Sugar Metabolism Pathways

Tillering is an important part in strawberry growth, and strawberries can reproduce nutritionally through stolons to generate genetically stable offspring. However, excessive tillering during the fruit-growing stage can negatively impact fruit yield and quality. In this study, different concentrations of exogenous rac-GR24 (GR24) are used to treat the strawberry plants. It was found that GR24 effectively inhibited the sprouting of strawberry stolons, while promoting the growth of the stems and leaves. Among the treatments, the most effective concentration was found to be 5 μmol/L GR24. This treatment resulted in a decrease in the glucose content in the strawberry crowns and also caused changes in the contents of two endogenous phytohormones, gibberellic acid (GA3) and trans-zeatin riboside (tZR). Transcriptome data further suggested that exogenous GR24 may inhibit strawberry plant tillering by affecting various phytohormone signaling pathways and the sugar metabolism pathway. In 5 μmol/L GR24-treated plants, the expression level of type-B response regulator (B-ARR) was down-regulated and the expression level of CYTOKININ RESPONSE 1 (CRE1), histidine-containing phosphotransfer protein (AHP), and type-A response regulator (A-ARR) were up-regulated, suggesting the inhibition of the cytokinin (CTK) signaling pathway. The down-regulation of auxin (AUX) and auxin response factor (ARF), as well as the up-regulation of auxin/indole-3-acetic acid (AUX/IAA), led to the inhibition of the indole-3-acetic acid (IAA) signaling pathway. Additionally, the up-regulation of pyrabactin resistance 1/ pyrabactin resistance 1-like (PYR/PYL), non-fermenting 1-related protein kinase 2 (SnRK2), and ABRE binding factors (ABF) and the down-regulation of protein phosphatase 2C (PP2C) were observed in the up-regulated abscisic acid (ABA) signaling pathways. In the sugar metabolism pathway, the up-regulation of invertase (INV), hexokinase (HK), and fructokinase (FRK) and the down-regulation of trehalase (TREH) and beta-amylase (BMY) led to a decreased glucose synthesis and an increased glucose consumption. Therefore, GR24 can effectively inhibit strawberry plant tillering through these pathways, making it an effective reagent for tillering inhibition.

Self S-RNase reduces the expression of two pollen-specific COBRA genes to inhibit pollen tube growth in pear

Due to self-incompatibility (SI) prevents self-fertilization, natural or artificial cross-pollination has been conducted in many orchards to stabilize fruit yield. However, it is still puzzled which routes of self S-RNase arresting pollen tube growth. Herein, 17 COBRA genes were isolated from pear genome. Of these genes, the pollen-specifically expressed PbCOB.A.1 and PbCOB.A.2 positively mediates pollen tube growth. The promoters of PbCOB.A.1 and/or PbCOB.A.2 were bound and activated by PbABF.E.2 (an ABRE-binding factor) and PbC2H2.K16.2 (a C2H2-type zinc finger protein). Notably, the expressions of PbCOB.A.1, PbCOB.A.2, and PbC2H2.K16.2 were repressed by self S-RNase, suggesting that self S-RNase reduces the expression of PbCOB.A.1 and PbCOB.A.2 by decreasing the expression of their upstream factors, such as PbC2H2.K16.2, to arrest pollen tube growth. PbCOB.A.1 or PbCOB.A.2 accelerates the growth of pollen tubes treated by self S-RNase, but can hardly affect level of reactive oxygen species and deploymerization of actin cytoskeleton in pollen tubes and cannot physically interact with any reported proteins involved in SI. These results indicate that PbCOB.A.1 and PbCOB.A.2 may not relieve S-RNase toxicity in incompatible pollen tube. The information provides a new route to elucidate the arresting pollen tube growth during SI reaction.Graphical

Arabidopsis ABRE-binding factors modulate salinity-induced inhibition of root hair growth by interacting with and suppressing RHD6

Soil salinity causes crop losses worldwide. Root hairs are the primary targets of salt stress, however, the signaling networks involved in the precise regulation of root hair growth and development by salinity are poorly understood. Here, we confirmed that salt stress inhibits the number and length of root hairs in Arabidopsis. We found that the master regulator of root hair development and growth, the RHD6 transcription factor, is involved in this process, as salt treatment largely compromised root hair overaccumulation in RHD6-overexpressing plants. Yeast-two-hybrid and co-immunoprecipitation analyses revealed that RHD6 physically interacts with ABF proteins, the master transcription factors in abscisic acid signaling, which is involved in tolerance to several stresses including salinity. Phenotypic analyses showed that ABF proteins, which function upstream of RHD6, positively modulate the salinity-induced inhibition of root hair development. Further analyses showed that ABF3 suppresses the transcriptional activation activity of RHD6, thereby regulating the expression of genes related to root hair development. Overexpression of ABF3 reduced the root hair-overgrowing phenotype of RHD6-overexpressing plants. Collectively, our results demonstrate an essential signaling module in which ABF proteins directly suppress the transcriptional activation activity of RHD6 to reduce the length and number of root hairs under salt stress conditions.

Identification of ABF/AREB gene family in tomato (Solanum lycopersicum L.) and functional analysis of ABF/AREB in response to ABA and abiotic stresses.

Abscisic acid (ABA) is a plant hormone that plays an important regulatory role in plant growth and stress response. The AREB (ABA-responsive element binding protein)/ABF (ABRE-binding factor) are important ABA-signaling components that participate in abiotic stress response. However, genome-scale analysis of ABF/AREB has not been systemically investigated in tomato. This study was conducted to identify tomato ABF/AREB family members and analyze their response to ABA and abiotic stresses. The results show that a total of 10 ABF/AREB members were identified in tomato, which are randomly distributed on five chromosomes. Domain analysis showed that these members exhibit high protein similarity, especially in the basic leucine zipper (bZIP) domain region. Subcellular localization analysis indicated that all 10 ABF/AREB members are localized in the nucleus. Phylogenetic tree analysis showed that tomato ABF/AREB genes are divided into two groups, and they are similar with the orthologs of other plants. The analysis of cis-acting elements showed that most tomato ABF/AREB genes contain a variety of hormones and stress-related elements. Expression profiles of different tissues indicated that SlABF2 and SlABF10 play an important role in fruit ripening. Finally, qRT-PCR analysis revealed that 10 tomato ABF/AREB genes respond to ABA, with SlABF3 being the most sensitive. SlABF3, SlABF5 and SlABF10 positively respond to salt and cold stresses. SlABF1, SlABF3 and SlABF10 are significantly induced under UV radiation treatment. SlABF3 and SlABF5 are significantly induced in osmotic stress. Overall, this study may provide insight into the role of tomato ABF/AREB homologues in plant response to abiotic stresses, which laid a foundation for future functional study of ABF/AREB in tomato.