Abscisic Acid Biosynthesis Genes Research Articles

Regulatory role of Prunus mume DAM6 on lipid body accumulation and phytohormone metabolism in the dormant vegetative meristem.

Bud dormancy is a crucial process in the annual growth cycle of woody perennials. In Rosaceae fruit tree species, DORMANCY-ASSOCIATED MADS-box (DAM) transcription factor genes regulating bud dormancy have been identified, but their molecular roles in meristematic tissues have not been thoroughly characterized. In this study, molecular and physiological analyses of transgenic apple plants overexpressing the Japanese apricot DAM6 gene (PmDAM6) and Japanese apricot cultivars and F1 individuals with contrasting dormancy characteristics revealed the metabolic pathways controlled by PmDAM6. Our transcriptome analysis and transmission electron microscopy examination demonstrated that PmDAM6 promotes the accumulation of lipid bodies and inhibits cell division in the dormant vegetative meristem by down-regulating the expression of lipid catabolism genes (GDSL ESTERASE/LIPASE and OIL BODY LIPASE) and CYCLIN genes, respectively. Our findings also indicate PmDAM6 promotes abscisic acid (ABA) accumulation and decreases cytokinin (CTK) accumulation in vegetative buds by up-regulating the expression of the ABA biosynthesis gene ARABIDOPSIS ALDEHYDE OXIDASE and the CTK catabolism gene CYTOKININ DEHYDROGENASE, while also down-regulating the expression of the CTK biosynthesis genes ISOPENTENYL TRANSFERASE (IPT) and CYP735A. Additionally, PmDAM6 modulates gibberellin (GA) metabolism by up-regulating GA2-OXIDASE expression and down-regulating GA3-OXIDASE expression. Furthermore, PmDAM6 may also indirectly promote lipid accumulation and restrict cell division by limiting the accumulation of CTK and GA in buds. In conclusion, using our valuable genetic platform, we clarified how PmDAM6 modifies diverse cellular processes, including lipid catabolism, phytohormone (ABA, CTK, and GA) biosynthesis and catabolism, and cell division, in the dormant vegetative meristem.

A wheat heat shock transcription factor gene, TaHsf-7A, regulates seed dormancy and germination

Heat shock transcription factors (Hsfs) play multifaceted roles in plant growth, development, and responses to environmental factors. However, their involvement in seed dormancy and germination processes has remained elusive. In this study, we identified a wheat class B Hsf gene, TaHsf-7A, with higher expression in strong-dormancy varieties compared to weak-dormancy varieties during seed imbibition. Specifically, TaHsf-7A expression increased during seed dormancy establishment and subsequently declined during dormancy release. Through the identification of a 1-bp insertion (ins)/deletion (del) variation in the coding region of TaHsf-7A among wheat varieties with different dormancy levels, we developed a CAPS marker, Hsf-7A-1319, resulting in two allelic variations: Hsf-7A-1319-ins and Hsf-7A-1319-del. Notably, the allele Hsf-7A-1319-ins correlated with a reduced seed germination rate and elevated dormancy levels, while Hsf-7A-1319-del exhibited the opposite trend across 175 wheat varieties. The association of TaHsf-7A allelic status with seed dormancy and germination levels was confirmed in various genetically modified species, including Arabidopsis, rice, and wheat. Results from the dual luciferase assay demonstrated notable variations in transcriptional activity among transformants harboring distinct TaHsf-7A alleles. Furthermore, the levels of abscisic acid (ABA) and gibberellin (GA), along with the expression levels of ABA and GA biosynthesis genes, showed significant differences between transgenic rice lines carrying different alleles of TaHsf-7A. These findings represent a significant step towards a comprehensive understanding of TaHsf-7A's involvement in the dormancy and germination processes of wheat seeds.

Bacillus cereus NJ01 induces SA- and ABA-mediated immunity against bacterial pathogens through the EDS1-WRKY18 module

Emerging evidence suggests a beneficial role of rhizobacteria in ameliorating plant disease resistance in an environment-friendly way. In this study, we characterize a rhizobacterium, Bacillus cereus NJ01, that enhances bacterial pathogen resistance in rice and Arabidopsis. Transcriptome analyses show that root inoculation of NJ01 induces the expression of salicylic acid (SA)- and abscisic acid (ABA)-related genes in Arabidopsis leaves. Genetic evidence showed that EDS1, PAD4, and WRKY18 are required for B.cereus NJ01-induced bacterial resistance. An EDS1-PAD4 complex interacts with WRKY18 and enhances its DNA binding activity. WRKY18 directly binds to the W box in the promoter region of the SA biosynthesis gene ICS1 and ABA biosynthesis genes NCED3 and NCED5 and contributes to the NJ01-induced bacterial resistance. Taken together, our findings indicate a role of the EDS1/PAD4-WRKY18 complex in rhizobacteria-induced disease resistance.

Strigolactone and abscisic acid synthesis and signaling pathways are enhanced in the wheat oligo-tillering mutant ot1

Tiller number greatly contributes to grain yield in wheat. Using ethylmethanesulfonate mutagenesis, we previously discovered the oligo-tillering mutant ot1. The tiller number was significantly lower in ot1 than in the corresponding wild type from the early tillering stage until the heading stage. Compared to the wild type, the thousand-grain weight and grain length were increased by 15.41% and 31.44%, respectively, whereas the plant height and spike length were decreased by 26.13% and 37.25%, respectively. Transcriptomic analysis was conducted at the regreening and jointing stages to identify differential expressed genes (DEGs). Functional enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases showed differential expression of genes associated with ADP binding, transmembrane transport, and transcriptional regulation during tiller development. Differences in tiller number in ot1 led to the upregulation of genes in the strigolactone (SL) and abscisic acid (ABA) pathways. Specifically, the SL biosynthesis genes DWARF (D27), D17, D10, and MORE AXILLARY GROWTH 1 (MAX1) were upregulated by 3.37- to 8.23-fold; the SL signal transduction genes D14 and D53 were upregulated by 1.81- and 1.32-fold, respectively; the ABA biosynthesis genes 9-CIS-EPOXICAROTENOID DIOXIGENASE 3 (NCED3) and NCED5 were upregulated by 1.66- and 3.4-fold, respectively; and SNF1-REGULATED PROTEIN KINASE2 (SnRK2) and PROTEIN PHOSPHATASE 2C (PP2C) genes were upregulated by 1.30- to 4.79-fold. This suggested that the tiller number reduction in ot1 was due to alterations in plant hormone pathways. Genes known to promote tillering growth were upregulated, whereas those known to inhibit tillering growth were downregulated. For example, PIN-FORMED 9 (PIN9), which promotes tiller development, was upregulated by 8.23-fold in ot1; Ideal Plant Architecture 1 (IPA1), which inhibits tiller development, was downregulated by 1.74-fold. There were no significant differences in the expression levels of TILLER NUMBER 1 (TN1) or TEOSINTE BRANCHED 1 (TB1), indicating that the tiller reduction in ot1 was not controlled by known genes. Our findings provide valuable data for subsequent research into the genetic bases and regulatory mechanisms of wheat tillering.

Differential expression of antimicrobial metabolites, phenylpropanoid and phytohormone metabolic pathway genes determines resistance or susceptibility to Ascochyta rabiei in chickpea

AbstractBlight caused by Ascochyta rabiei is a major constraint in the productivity of chickpea (Cicer arietinum). The mechanisms governing resistance/susceptibility to blight in chickpea are poorly understood. We used a blight‐resistant (HC1) and a blight‐susceptible (GPF2) genotype of chickpea and genes of pathogenesis‐related proteins (PRPs), phenylpropanoid pathway metabolites, abscisic acid (ABA), gibberellic acid (GA) and jasmonic acid (JA) to understand the role of these in A. rabiei resistance/susceptibility. The JA, ABA and GA biosynthesis genes of chickpea were retrieved, characterized and gene‐specific primers were used for transcriptional studies. Gene expression revealed that chickpea activated its defences rather quickly and well before initiation of spore germination. In resistant HC1, the majority of the JA, GA and phenylpropanoid pathway genes had peak maxima at 2 h post‐inoculation (hpi) whereas PRPs/defence genes had peak maxima at 24/36 hpi implying that defence to A. rabiei in chickpea is composed of a two‐tier system separated by time: immediately after spore attachment and at or just prior to host penetration. Unlike HC1, susceptible GPF2 was late in activation of defence responses or did not activate them. Another striking difference between HC1 and GPF2 was up‐regulation of ABA biosynthesis genes in inoculated GPF2 and down‐regulation in HC1. This study revealed that phenylpropanoids, PRPs, JA, 8‐(1R,2R)‐3‐oxo‐2‐(Z)‐pent‐2‐enyl cyclopentyl octanoate, (15Z)‐12‐oxophyto‐10,15‐dienoic acid and methyl‐jasmonate govern resistance to A. rabiei in chickpea whereas ABA governs susceptibility.

Transcriptomic and physiological analyses reveal that jasmonic acid and abscisic acid coordinately regulate cold stress response in Myriophyllum aquaticum

Myriophyllum aquaticum, renowned for its ability to purify aquaculture wastewater, faces a significant challenge due to its susceptibility to cold stress. However, the molecular mechanisms underlying M. aquaticum's response to cold stress remain poorly understood. In this study, we unraveled the molecular mechanisms governing M. aquaticum's response to cold stress through transcriptome sequencing and physiological analyses. Our investigation revealed 12,684 differentially expressed genes during cold stress. Gene ontology and KEGG analyses demonstrated the involvement of plant hormone signaling and transcriptional reprogramming related genes in M. aquaticum's response to cold stress. Further investigations highlighted the role of jasmonic acid (JA) and abscisic acid (ABA) in M. aquaticum's cold acclimation. Firstly, cold stress significantly increased endogenous levels of JA and ABA in M. aquaticum plants. Secondly, the transcript levels of several crucial JA and ABA signaling genes were prominently elevated, as shown by expression profiling and qRT-PCR analyses. Thirdly, the application of exogenous JA or ABA effectively mitigated foliar damage and improved cold tolerance in M. aquaticum plants. Furthermore, the expression of JA and ABA biosynthesis and signaling genes was significantly upregulated in JA- or ABA-pretreated plants when exposed to cold stress. Collectively, our findings provide evidence that JA and ABA contribute to the cold acclimation of M. aquaticum plants. Our research provides insights into the molecular mechanisms underlying cold acclimation of M. Aquaticum plants and presents a novel strategy to improve their cold tolerance, thereby expanding their potential application in phytoremediation efforts in high latitude areas.

Voltage-dependent anion channel 3 (VDAC3) mediates P. syringae induced ABA-SA signaling crosstalk in Arabidopsis thaliana

Pathogen severely affects plant mitochondrial processes including respiration, however, the roles and mechanism of mitochondrial protein during the immune response remain largely unexplored. The interplay of plant hormone signaling during defense is an outcome of plant pathogen interaction. We recently discovered that the Arabidopsis calcineurin B-like interacting protein kinase 9 (AtCIPK9) interacts with the voltage-dependent anion channel 3 (AtVDAC3) and inhibits MV-induced oxidative damage. Here we report the characterization of AtVDAC3 in an antagonistic interaction pathway between abscisic acid (ABA) and salicylic acid (SA) signaling in Pseudomonas syringae -Arabidopsis interaction. In this study, we observed that mutants of AtVDAC3 were highly susceptible to Pseudomonas syringae infection as compared to the wild type (WT) Arabidopsis plants. Transcripts of VDAC3 and CIPK9 were inducible upon ABA application. Following pathogen exposure, expression analyses of ABA and SA biosynthesis genes indicated that the function of VDAC3 is required for isochorisimate synthase 1 (ICS1) expression but not for Nine-cis-epoxycaotenoid dioxygenase 3 (NCED3) expression. Despite the fact that vdac3 mutants had increased NCED3 expression in response to pathogen challenge, transcripts of ABA sensitive genes such as AtRD22 and AtRAB18 were downregulated even after exogenous ABA application. VDAC3 is required for ABA responsive genes expression upon exogenous ABA application. We also found that Pseudomonas syringae-induced SA signaling is downregulated in vdac3 mutants since overexpression of VDAC3 resulted in hyperaccumulation of Pathogenesis related gene1 (PR1) transcript. Interestingly, ABA application prior to P. syringae inoculation resulted in the upregulation of ABA responsive genes like Responsive to ABA18 (RAB18) and Responsive to dehydration 22 (RD22). Intriguingly, in the absence of AtVDAC3, Pst challenge can dramatically increase ABA-induced RD22 and RAB18 expression. Altogether our results reveal a novel Pathogen-SA-ABA interaction pathway in plants. Our findings show that ABA plays a significant role in modifying plant-pathogen interactions, owing to cross-talk with the biotic stress signaling pathways of ABA and SA.

The overexpression of SlBRI1 driven by Atrd29A promoter-transgenic plants improves the chilling stress tolerance of tomato.

Overexpression of SlBRI1 driven by the Atrd29A promoter could increase the cold resistance of tomato plants during chilling stress but did not improve the expression of SlBRI1 and plant growth under normal conditions. Low temperature is the main limiting factor severely affecting tomato plant development, growth, and fruit quality in winter and spring. Brassinosteroids (BRs) and key BR signaling genes positively regulate tomato plant development and response to chilling stress. Brassinosteroid-insensitive 1 (BRI1) is a major BR receptor that initiates BR signaling. Our results showed that overexpression of SlBRI1 driven by the Atrd29A promoter in transgenic plants did not increase the expression of SlBRI1 under normal conditions but rapidly induced the expression of SlBRI1 during chilling stress. The degree of wilting was lower in Atrd29A promoter-transgenic plants than in wild-type (WT) plants after chilling stress. Atrd29A promoter-transgenic plants exhibited low relative electrolyte leakage and reactive oxygen species (ROS) accumulation under chilling stress. Transgenic plants showed higher photosynthetic ability and antioxidant enzyme activity than WT plants under chilling stress. The BR content and expression levels of key genes involved in BR biosynthesis in Atrd29A-promoter transgenic plants were significantly lower than those in WT plants during chilling stress. The abscisic acid (ABA) content and expression levels of key ABA biosynthesis genes in the Atrd29A promoter-transgenic plants were significantly higher than those in the WT plants during chilling stress. In addition, Atrd29A promoter-transgenic plants positively enhanced the expression levels of ICE-CBF-COR cold-responsive pathway genes. Therefore, the overexpression of SlBRI1 driven by the Atrd29A promoter in transgenic plants can be a valuable tool for reducing chilling stress.

A 14-3-3 Protein-Encoding Gene, BdGF14g, Confers Better Drought Tolerance by Regulating ABA Biosynthesis and Signaling

Abscisic acid (ABA), a phytohormone, enacts a cardinal function in coping with abiotic stress. 14-3-3 proteins can interact with ABA-responsive-element-binding transcription factors (ABFs), a chief constituent of ABA signaling, and play critical roles in the dehydration response involving ABA signaling. Meanwhile, whether and how 14-3-3 proteins regulate ABA signaling to respond to aridity stress is yet to be fully investigated. Herein, BdGF14g, a 14-3-3 gene induced by ABA, H2O2, and PEG treatments, was identified in Brachypodium distachyon (B. distachyon). Overexpression of BdGF14g improved drought stress tolerance in tobacco plants, with a higher survival rate, longer root length, enhanced cell membrane stability, and increased antioxidase activity compared with non-transgenic controls in coping with dehydration. Both drought and exogenous ABA treatments resulted in smaller stomatal apertures in BdGF14g-transgenic lines. Additionally, when an ABA biosynthesis inhibitor was added, the better growth statuses, less H2O2 accumulation, and higher activities of catalase and superoxide dismutase under mannitol stress disappeared. Moreover, BdGF14g interacted with NtABF2, upregulated the endogenous ABA content, and enhanced the transcription of ABA-related genes, including NtNCED1, a crucial ABA biosynthesis gene, under drought conditions. In conclusion, BdGF14g acts as a positive factor in the water deficiency response by affecting ABA biosynthesis and signaling in tobacco plants.

Unveiling the toxic effects, physiological responses and molecular mechanisms of tobacco (Nicotiana tabacum) in exposure to organic ultraviolet filters

Exposure to organic ultraviolet (UV) filters has raised concerns due to their potential adverse effects on environments. However, their toxic mechanisms on plants remain elusive. In this study, using integrative physiological and transcriptomic approaches we investigated the physiological and molecular responses to three representative UV filters, namely oxybenzone (OBZ), avobenzone (AVB), and octinoxate (OMC), in an agricultural model plant tobacco. The exposure to UV filters disrupts the functionality of photosystem reaction centers and the light-harvesting apparatus. Concurrently, UV filters exert a suppressive effect on the expression of genes encoding Rubisco and Calvin-Benson cycle enzymes, resulting in a decreased efficiency of the Calvin-Benson cycle and consequently hampering the process of photosynthesis. Exposure to UV filters leads to significant generation of reactive oxygen species within tobacco leaves and downregulation of oxidoreductase activities. Moreover, UV filters promote abscisic acid (ABA) accumulation by inducing the expression of ABA biosynthesis genes whereas repress indole-3-acetic acid (IAA) biosynthesis gene expression, which induce leaf yellowing and slow plant growth. In summary, the organic UV filters exert toxic effects on tobacco growth by inhibiting chlorophyll synthesis, photosynthesis, and the Calvin-Benson cycle, while generating excessive reactive oxygen species. This study sheds light on the toxic and tolerance mechanisms of UV filters in agricultural crops.

Expression pattern of candidate genes and their correlation with various metabolites of abscisic acid biosynthetic pathway under drought stress in rice

AbstractDrought hampers global rice production. Abscisic acid (ABA) plays versatile roles under different environmental stresses. While the link between drought and ABA is known, its effect on ABA biosynthesis genes and metabolites is unclear. This study explored the impact of drought on various metabolites, namely beta‐carotene, zeaxanthin, antheraxanthin, violaxanthin, neoxanthin, and candidate genes viz. zeaxanthin epoxidase (ZEP) and 9‐cis epoxycarotenoid dioxygenase (NCED) of ABA biosynthesis pathway in rice cultivars (N22 and IR64) at anthesis {65 DAT (Days after transplanting)} with different stress levels. In stressed plants, zeaxanthin significantly increased (92%), while the concentration of beta‐carotene, antheraxanthin, violaxanthin and neoxanthin decreased as drought stress progressed. The concentration of metabolites in roots was notably lower than in leaves in both genotypes. The ZEP expression was upregulated in roots (8.24‐fold) under drought stress. Among five NCED isoforms, NCED3 showed significant upregulation (7.29‐fold) in leaf and root tissue. NCED1 was significantly downregulated as stress progressed and was negatively correlated with ABA accumulation. NCED2, NCED4 and NCED5 showed no significant change in their expression. Drying and rolling of rice leaves was observed after imparting drought stress. The findings revealed that drought stress significantly influenced the expression of candidate genes and the concentration of metabolites of the ABA biosynthesis pathway. There was a significantly higher accumulation of ABA in N22 leaves (47%) and roots (30%) compared to IR64. The N22, a drought‐tolerant genotype, exhibited significantly higher concentrations of intermediates and demonstrated increased expression of ZEP and NCED3, potentially contributing to its resilience against drought.

The NLR immune receptor ADR1 and lipase-like proteins EDS1 and PAD4 mediate stomatal immunity in Nicotiana benthamiana and Arabidopsis.

In the presence of pathogenic bacteria, plants close their stomata to prevent pathogen entry. Intracellular nucleotide-binding leucine-rich repeat (NLR) immune receptors recognize pathogenic effectors and activate effector-triggered immune responses. However, the regulatory and molecular mechanisms of stomatal immunity involving NLR immune receptors are unknown. Here, we show that the Nicotiana benthamiana RPW8-NLR central immune receptor ACTIVATED DISEASE RESISTANCE 1 (NbADR1), together with the key immune proteins ENHANCED DISEASE SUSCEPTIBILITY 1 (NbEDS1) and PHYTOALEXIN DEFICIENT 4 (NbPAD4), plays an essential role in bacterial pathogen- and flg22-induced stomatal immunity by regulating the expression of salicylic acid (SA) and abscisic acid (ABA) biosynthesis or response-related genes. NbADR1 recruits NbEDS1 and NbPAD4 in stomata to form a stomatal immune response complex. The transcription factor NbWRKY40e, in association with NbEDS1 and NbPAD4, modulates the expression of SA and ABA biosynthesis or response-related genes to influence stomatal immunity. NbADR1, NbEDS1, and NbPAD4 are required for the pathogen infection-enhanced binding of NbWRKY40e to the ISOCHORISMATE SYNTHASE 1 promoter. Moreover, the ADR1-EDS1-PAD4 module regulates stomatal immunity in Arabidopsis (Arabidopsis thaliana). Collectively, our findings show the pivotal role of the core intracellular immune receptor module ADR1-EDS1-PAD4 in stomatal immunity, which enables plants to limit pathogen entry.

Comparative transcriptome analysis of high- and low-embryogenic Hevea brasiliensis genotypes reveals involvement of phytohormones in somatic embryogenesis

BackgroundRubber plant (Hevea brasiliensis) is one of the major sources of latex. Somatic embryogenesis (SE) is a promising alterative to its propagation by grafting and seed. Phytohormones have been shown to influence SE in different plant species. However, limited knowledge is available on the role of phytohormones in SE in Hevea. The anther cultures of two Hevea genotypes (Yunyan 73477-YT and Reken 628-RT) with contrasting SE rate were established and four stages i.e., anthers (h), anther induced callus (y), callus differentiation state (f), and somatic embryos (p) were studied. UPLC-ESI-MS/MS and transcriptome analyses were used to study phytohormone accumulation and related expression changes in biosynthesis and signaling genes.ResultsYT showed higher callus induction rate than RT. Of the two genotypes, only YT exhibited successful SE. Auxins, cytokinins (CKs), abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), gibberellins (GAs), and ethylene (ETH) were detected in the two genotypes. Indole-3-acetic acid (IAA), CKs, ABA, and ETH had notable differences in the studied stages of the two genotypes. The differentially expressed genes identified in treatment comparisons were majorly enriched in MAPK and phytohormone signaling, biosynthesis of secondary metabolites, and metabolic pathways. The expression changes in IAA, CK, ABA, and ETH biosynthesis and signaling genes confirmed the differential accumulation of respective phytohormones in the two genotypes.ConclusionThese results suggest potential roles of phytohormones in SE in Hevea.

Nitric oxide regulates the lignification and carotenoid biosynthesis of postharvest carrot (Daucus carota L.)

The carrot is an important horticultural crop of the Apiaceae family, possessing considerable nutritional and economic value. Unfortunately, the decline in the postharvest quality has resulted in a decrease in the desirability of carrots and further food wastage. Nitric oxide (NO) plays a crucial role in alleviating the senescence and reducing losses of postharvest horticultural products, but its impact on the postharvest quality of carrots has not been reported. In this study, the effects of treatment with ddH2O, varying concentrations of sodium nitroprusside (SNP), and carboxy-PTIO (cPTIO) on the whiteness index, weight loss, and sensory scoring were evaluated, and a concentration of 1.5 mM SNP treatment preserved the appearance quality of postharvest carrots. Further analysis revealed that SNP treatment led to an increase in endogenous NO content by promoting nitrate reductase activity, which subsequently enhanced the expression of DcPSY1, DcPDS1, DcZDS1, DcCRTISO1, and DcLCYB1 and increased the levels of total carotenoid, α-carotenoid, and β-carotenoid. The alternation of carotenoids both increased abscisic acid (ABA) level by promoting the expression of ABA biosynthesis genes, but also hindered the generation of hydrogen peroxide and superoxide anion. Meanwhile, the expression of lignin biosynthesis genes was downregulated in SNP treatment group, resulting in postharvest carrots with lower lignin content and a lower degree of cell lignification. Overall, our findings provide a theoretical basis for the application of NO in the postharvest preservation of carrots and shed light on the role of NO in regulating the synthesis mechanisms of carotenoids and lignin in postharvest carrots.

A group III WRKY transcription factor, SlWRKY52, positively regulates drought tolerance in tomato

Drought severely limits crop growth and development, reducing productivity. WRKY transcription factors play crucial roles in regulating diverse aspects of plant growth, development, and responses to stress. Despite this, the functions of tomato WRKYs (SlWRKYs) in response to drought stress remain incompletely understood. Thus, we isolated SlWRKY52, a member of the group III SlWRKYs from the tomato variety ‘Ailsa Craig’, and investigated its role in drought stress responses. SlWRKY52 is an unstable hydrophilic protein chiefly located in the nucleus, which promoter region features cis-acting elements engaged in drought stress response. It was expressed in all tomato tissues and its expression was rapidly induced by drought stress. SlWRKY52 overexpression lines conferred enhanced drought stress resistance in tomato: its involved in abscisic acid (ABA) synthesis, resulted in rapid, ABA-dependent stomatal closure, reduced leaf water loss, lessened photosynthetic damage, higher antioxidant enzyme activity, decreased oxidative damage parameters, increased osmoregulatory substance content, accelerated reactive oxygen species scavenging, and increased expression of regulatory interaction, ABA biosynthesis, and abiotic stress response-related genes. Conversely, the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 nuclease mutant lines of SlWRKY52 reduced drought stress tolerance. In conclusion, our findings suggest that SlWRKY52 acts as a positive regulator of drought tolerance in tomato and has the potential to be used as a target gene for further molecular breeding.

Auxin and abscisic acid play important roles in promoting glucose metabolism of reactivated young kernels of maize (Zea mays L.).

In maize, young kernels that are less competitive and have poor sink activity often abort. Studies have indicated that such poor competitiveness depends, in part, on the regulation by auxin (IAA) and abscisic acid (ABA). However, the mechanisms for such effects remain unclear. We used pollination-blocking and hand-pollination treatments accompanied by multi-omics and physiological tests, to identify underlying mechanism by which IAA and ABA, along with sugar signaling affect kernel development. Results showed that preventing pollination of the primary ears reactivated kernels in the secondary ears and altered both sugar metabolism and hormone signaling pathways. This was accompanied by increased enzyme activities in carbon metabolism and concentrations of glucose and starch, as well as increased levels of IAA and decreased levels of ABA in the reactivated kernels. Positive and negative correlations were observed between IAA, ABA contents and cell wall invertase (CWIN) activity, and glucose contents, respectively. In vitro culture revealed that the expression of genes involved in glucose utilization was upregulated by IAA, but downregulated by ABA. IAA could promote the expression of ABA signaling genes ZmPP2C9 and ZmPP2C13 but downregulated the expression of Zmnced5, an ABA biosynthesis gene, and ZmSnRK2.10, which is involved in ABA signal transduction. However, these genes showed opposite trends when IAA transport was inhibited. To summarize, we suggest a regulatory model for how IAA inhibits ABA metabolism by promoting the smooth utilization of glucose in reactivated young kernels. Our findings highlight the importance of IAA in ABA signaling by regulating glucose production and transport in maize.

ClSnRK2.3 negatively regulates watermelon fruit ripening and sugar accumulation.

Watermelon (Citrullus lanatus) as non-climacteric fruit is domesticated from the ancestors with inedible fruits. We previously revealed that the abscisic acid (ABA) signaling pathway gene ClSnRK2.3 might influence watermelon fruit ripening. However, the molecular mechanisms are unclear. Here, we found that the selective variation of ClSnRK2.3 resulted in lower promoter activity and gene expression level in cultivated watermelons than ancestors, which indicated ClSnRK2.3 might be a negative regulator in fruit ripening. Overexpression (OE) of ClSnRK2.3 significantly delayed watermelon fruit ripening and suppressed the accumulation of sucrose, ABA and gibberellin GA4 . Furthermore, we determined that the pyrophosphate-dependent phosphofructokinase (ClPFP1) in sugar metabolism pathway and GA biosynthesis enzyme GA20 oxidase (ClGA20ox) could be phosphorylated by ClSnRK2.3 and thereby resulting in accelerated protein degradation in OE lines and finally led to low levels of sucrose and GA4 . Besides that, ClSnRK2.3 phosphorylated homeodomain-leucine zipper protein (ClHAT1) and protected it from degradation to suppress the expression of the ABA biosynthesis gene 9'-cis-epoxycarotenoid dioxygenase 3 (ClNCED3). These results indicated that ClSnRK2.3 negatively regulated watermelon fruit ripening by manipulating the biosynthesis of sucrose, ABA and GA4 . Altogether, these findings revealed a novel regulatory mechanism in non-climacteric fruit development and ripening.

Physiological mechanism of melatonin attenuating to osmotic stress tolerance in soybean seedlings.

Drought is one of the most significant abiotic stress threatening to crop production worldwide. Soybean is a major legume crop with immense economic significance, but its production is highly dependent on optimum rainfall or abundant irrigation. As the global climate changes, it is more important to find solutions to make plants more resilient to drought. The prime aimed of the study is to investigate the effect of melatonin on drought tolerance in soybean and its potential mechanisms. Soybean seedlings were treated with 20% polyethylene glycol 6000 (PEG 6000) and subjected to osmotic stress (14 days) with or without 100 μM melatonin treatment. Our results revealed that melatonin supplementation significantly mitigated PEG-induced growth retardation and increased water absorption ability. Foliar application of melatonin also increased gas exchange and the chlorophyll fluorescence attributes by the mitigation of the osmotic-induced reduction of the reaction activity of photosystems I and II, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), electron transport activity, and photosynthetic efficiency. In addition, PEG-induced elevated production of reactive oxygen species (ROS) and malondialdehyde (MDA) content were significantly reversed by melatonin treatment. Equally important, melatonin boosted the antioxidant activities of soybean plants. Moreover, osmotic stress substantially increased abscisic acid (ABA) accumulation in roots and leaves, while melatonin-received plant leaves accumulated less ABA but roots content higher ABA. Similarly, melatonin significantly suppressed ABA biosynthesis and signaling gene expression in soybean exposed to drought stress. Furthermore, osmotic stress significantly suppressed plasmalemma (GmPIPs) and tonoplast aquaporin (GmTIPs) genes expression, and their transcript abundance was up-regulated by melatonin co-addition. Taken together, our results indicated that melatonin potentially improves drought tolerance of soybean through the regulation of ABA and aquaporin gene expression, increasing photosynthetic efficiency as well as enhancing water uptake efficiency.

Rice OsGA2ox9 regulates seed GA metabolism and dormancy.

Rice OsGA2ox9 regulates seed GA metabolism and dormancy.

Allantoin improves salinity tolerance in Arabidopsis and rice through synergid activation of abscisic acid and brassinosteroid biosynthesis.

Soil salinity stress is one of the major bottlenecks for crop production. Although, allantoin is known to be involved in nitrogen metabolism in plants, yet several reports in recent time indicate its involvement in various abiotic stress responses including salinity stress. However, the detail mechanism of allantoin involvement in salinity stress tolerance in plants is not studied well. Moreover, we demonstrated the role of exogenous application of allantoin as well as increased concentration of endogenous allantoin in rendering salinity tolerance in rice and Arabidopsis respectively, via., induction of abscisic acid (ABA) and brassinosteroid (BR) biosynthesis pathways. Exogenous application of allantoin (10µM) provides salt-tolerance to salt-sensitive rice genotype (IR-29). Transcriptomic data after exogenous supplementation of allantoin under salinity stress showed induction of ABA (OsNCED1) and BR (Oscytochrome P450) biosynthesis genes in IR-29. Further, the key gene of allantoin biosynthesis pathway i.e., urate oxidase of the halophytic species Oryza coarctata was also found to induce ABA and BR biosynthesis genes when over-expressed in transgenic Arabidopsis. Thus, indicating that ABA and BR biosynthesis pathways were involved in allantoin mediated salinity tolerance in both rice and Arabidopsis. Additionally, it has been found that several physio-chemical parameters such as biomass, Na+/K+ ratio, MDA, soluble sugar, proline, allantoin and chlorophyll contents were also associated with the allantoin-mediated salinity tolerance in urate oxidase overexpressed lines of Arabidopsis. These findings depicted the functional conservation of allantoin for salinity tolerance in both plant clades.