Abiotic Stress Tolerance In Plants Research Articles

Molecular Mechanisms of CBL-CIPK Signaling Pathway in Plant Abiotic Stress Tolerance and Hormone Crosstalk.

Abiotic stressors, including drought, salt, cold, and heat, profoundly impact plant growth and development, forcing elaborate cellular responses for adaptation and resilience. Among the crucial orchestrators of these responses is the CBL-CIPK pathway, comprising calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs). While CIPKs act as serine/threonine protein kinases, transmitting calcium signals, CBLs function as calcium sensors, influencing the plant's response to abiotic stress. This review explores the intricate interactions between the CBL-CIPK pathway and plant hormones such as ABA, auxin, ethylene, and jasmonic acid (JA). It highlights their role in fine-tuning stress responses for optimal survival and acclimatization. Building on previous studies that demonstrated the enhanced stress tolerance achieved by upregulating CBL and CIPK genes, we explore the regulatory mechanisms involving post-translational modifications and protein-protein interactions. Despite significant contributions from prior research, gaps persist in understanding the nuanced interplay between the CBL-CIPK system and plant hormone signaling under diverse abiotic stress conditions. In contrast to broader perspectives, our review focuses on the interaction of the pathway with crucial plant hormones and its implications for genetic engineering interventions to enhance crop stress resilience. This specialized perspective aims to contribute novel insights to advance our understanding of the potential of the CBL-CIPK pathway to mitigate crops' abiotic stress.

Medicago truncatula β-glucosidase 17 contributes to drought and salt tolerance through antioxidant flavonoid accumulation.

Flavonoids are usually present in forms of glucosides in plants, which could be catabolized by β-glucosidase (BGLU) to form their corresponding flavonoid aglycones. In this study, we isolated three abiotic-responsive BGLU genes (MtBGLU17, MtBGLU21and MtBGLU22) from Medicago truncatula, and found only the recombinant MtBGLU17 protein could catalyse the hydrolysis of flavonoid glycosides. The recombinant MtBGLU17 protein is active towards a variety of flavonoid glucosides, including glucosides of flavones (apigenin and luteolin), flavonols (kaempferol and quercetin), isoflavones (genistein and daidzein)and flavanone (naringenin). In particular, the recombinant MtBGLU17 protein preferentially hydrolyses flavonoid-7-O-glucosides over their corresponding 3-O-glucosides. The content of luteoin-7-O-glucoside was reduced in the MtBGLU17 overexpression plants but increased in the Tnt-1 insertional mutant lines, whereas luteoin content was increased in the MtBGLU17 overexpression plants but reduced in the Tnt-1 insertional mutant lines. Under drought and salt (NaCl) treatment, the MtBGLU17 overexpression lines showed relatively higher DPPH content, and higher CAT and SOD activity than the wild type control. These results indicated that overexpression lines of MtBGLU17 possess higher antioxidant activity and thus confer drought and salt tolerance, implying MtBGLU17 could be potentially used as a candidate gene to improve plant abiotic stress tolerance.

Comparative miRNome and transcriptome analyses reveal the expression of novel miRNAs in the panicle of rice implicated in sustained agronomic performance under terminal drought stress.

Differential expression of 128 known and 111 novel miRNAs in the panicle of Nagina 22 under terminal drought stress targeting transcription factors, stress-associated genes, etc., enhances drought tolerance and helps sustain agronomic performance under terminal drought stress. Drought tolerance is a complex multigenic trait, wherein the genes are fine-tuned by coding and non-coding components in mitigating deleterious effects. MicroRNA (miRNA) controls gene expression at post-transcriptional level either by cleaving mRNA (transcript) or by suppressing its translation. miRNAs are known to control developmental processes and abiotic stress tolerance in plants. To identify terminal drought-responsive novel miRNA in contrasting rice cultivars, we constructed small RNA (sRNA) libraries from immature panicles of drought-tolerant rice [Nagina 22 (N 22)] and drought-sensitive (IR 64) cultivars grown under control and terminal drought stress. Our analysis of sRNA-seq data resulted in the identification of 169 known and 148 novel miRNAs in the rice cultivars. Among the novel miRNAs, 68 were up-regulated while 43 were down-regulated in the panicle of N 22 under stress. Interestingly, 31 novel miRNAs up-regulated in N 22 were down-regulated in IR 64, whereas 4 miRNAs down-regulated in N 22 were up-regulated in IR 64 under stress. To detect the effects of miRNA on mRNA expression level, transcriptome analysis was performed, while differential expression of miRNAs and their target genes was validated by RT-qPCR. Targets of the differentially expressed miRNAs include transcription factors and stress-associated genes involved in cellular/metabolic/developmental processes, response to abiotic stress, programmed cell death, photosynthesis, panicle/seed development, and grain yield. Differential expression of the miRNAs could be validated in an independent set of the samples. The findings might be useful in genetic improvement of drought-tolerant rice.

KASP: a high-throughput genotyping system and its applications in major crop plants for biotic and abiotic stress tolerance.

Advances in plant molecular breeding have resulted in the development of new varieties with superior traits, thus improving the crop germplasm. Breeders can screen a large number of accessions without rigorous and time-consuming phenotyping by marker-assisted selection (MAS). Molecular markers are one of the most imperative tools in plant breeding programmes for MAS to develop new cultivars possessing multiple superior traits. Single nucleotide polymorphisms (SNPs) are ideal for MAS due to their low cost, low genotyping error rates, and reproducibility. Kompetitive Allele Specific PCR (KASP) is a globally recognized technology for SNP genotyping. KASP is an allele-specific oligo extension-based PCR assay that uses fluorescence resonance energy transfer (FRET) to detect genetic variations such as SNPs and insertions/deletions (InDels) at a specific locus. Additionally, KASP allows greater flexibility in assay design, which leads to a higher success rate and the capability to genotype a large population. Its versatility and ease of use make it a valuable tool in various fields, including genetics, agriculture, and medical research. KASP has been extensively used in various plant-breeding applications, such as the identification of germplasm resources, quality control (QC) analysis, allele mining, linkage mapping, quantitative trait locus (QTL) mapping, genetic map construction, trait-specific marker development, and MAS. This review provides an overview of the KASP assay and emphasizes its validation in crop improvement related to various biotic and abiotic stress tolerance and quality traits.

Arbuscular mycorrhizal fungi enhanced resistance to low-temperature weak-light stress in snapdragon (Antirrhinum majus L.) through physiological and transcriptomic responses.

Low temperature (LT) and weak light (WL) seriously affects the yield and quality of snapdragon in winter greenhouse. Arbuscular mycorrhizal fungi (AMF) exert positive role in regulating growth and enhancing abiotic stress tolerance in plants. Nevertheless, the molecular mechanisms by AMF improve the LT combined with WL (LTWL) tolerance in snapdragon remain mostly unknown. We compared the differences in root configuration, osmoregulatory substances, enzymatic and non-enzymatic antioxidant enzyme defense systems and transcriptome between AMF-inoculated and control groups under LT, WL, low light, and LTWL conditions. Our analysis showed that inoculation with AMF effectively alleviated the inhibition caused by LTWL stress on snapdragon root development, and significantly enhanced the contents of soluble sugars, soluble proteins, proline, thereby maintaining the osmotic adjustment of snapdragon. In addition, AMF alleviated reactive oxygen species damage by elevating the contents of AsA, and GSH, and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR). RNA-seq analysis revealed that AMF regulated the expression of genes related to photosynthesis (photosystem I related proteins, photosystem II related proteins, chlorophyll a/b binding protein), active oxygen metabolism (POD, Fe-SOD, and iron/ascorbate family oxidoreductase), plant hormone synthesis (ARF5 and ARF16) and stress-related transcription factors gene (bHLH112, WRKY72, MYB86, WRKY53, WRKY6, and WRKY26) under LTWL stress. We concluded that mycorrhizal snapdragon promotes root development and LTWL tolerance by accumulation of osmoregulatory substances, activation of enzymatic and non-enzymatic antioxidant defense systems, and induction expression of transcription factor genes and auxin synthesis related genes. This study provides a theoretical basis for AMF in promoting the production of greenhouse plants in winter.

Contrasting Regulation of Phaseolus vulgaris Root Hydraulic Properties Under Drought and Saline Conditions by Three Arbuscular Mycorrhizal Fungal Species From Soils with Divergent Moisture Regime

Abstract Purpose Arbuscular mycorrhizal fungi (AMF) may help plants to overcome abiotic stresses, in part by improving their water uptake capacity. However how different AMF isolated from different climatic regions regulate plant abiotic stress tolerance and water uptake capacity is barely studied. The aim of this study was to reveal how three AMF isolated from two Mediterranean climate locations contrasting in annual precipitation, modify bean (Phaseolus vulgaris L.) root hydraulic properties facing drought and salinity. Methods Rhizophagus intraradices (Ri) and Funneliformis mosseae (Fm) were isolated from a humid area, whereas Claroideoglomus etunicatum (Ce) was isolated from a dry location. All plants (inoculated or not) were subjected to four days of withholding water or salt treatment. Root hydraulic properties including root hydraulic conductivity and aquaporin expression and abundance were determined. Results All three AMF isolate induced significant differences in plant physiology regardless their different mycorrhizal colonization extent. Drought treatment diminished root hydraulic conductivity and only Fm inoculated plants featured measurable amount of sap exudate. After salt irrigation, AMF inoculation counterbalanced the drop of root hydraulic conductivity. In such situation two AMF, Fm and Ce, presented lowered phosphorylated (Ser-283) PIP2 AQP amount. AQP gene expression highlighted the importance of PvPIP1;2 and PvPIP2;3 plasticity in plants facing osmotic stress. After drought treatment AMF species from the humid location, Ri and Fm, improved plant water status and Fm enhanced root hydraulic conductivity, whereas all AMF performed similarly after salt irrigation, enhancing stomatal conductance and root hydraulic conductivity. Conclusion Under drought conditions, the AMF isolates from humid regions were the ones that most effectively improved plant water relations. However, under salt stress, all three AMF isolates exhibited similar behavior. Therefore, to some extent, the climatic origin of the AMF could have influenced the response of host plants to drought stress, suggesting that those originating from dry areas may not necessarily be the most efficient.

Prediction of drought regulating gene (s) in barley (Hordeum vulgare L.) using express sequence tags (ESTs) through in silico approaches

Climate change is a major current issue in the world, affecting the availability and stability of food. It leads to the most damaging abiotic stress for the ecosystem and the one that results in the greatest output loss is drought. Barley was once thought to be an abiotic stress-tolerant plant but the production of barley dropped significantly due to drought-stress. In this study, a computational method was used to predict the genes in barley that are associated with drought stress. The expressed sequence tags (ESTs) were investigated to identify the gene expression profiling in barley during drought stress. Various software, tools, and servers were used to predict the genes using ESTs, which were responsive to drought stress. The TFcat and blast2GO tools were used to predict transcription factors and enzymes respectively. Phytozome and plantCARE databases were used to validate newly predicted novel candidate genes using promoter studies. By using the Ensemble plant genome database, new genes related to drought stress were discovered. There were only 37 locations in the barley genome that had candidate genes. According to the promoter analysis, twenty nine genes had more than ten cis acting controlling elements that was related to drought stress in various plants. The promoter study showed that 29 out of 37 genes contained more than 10 cis-acting regulatory elements involved in drought stress in different plants. These findings will be helpful to identify the novel drought stress tolerant gene in barley that may play an important role in developing new varieties in near future.

The MYB-CC Transcription Factor PHOSPHATE STARVATION RESPONSE-LIKE 7 (PHL7) Functions in Phosphate Homeostasis and Affects Salt Stress Tolerance in Rice.

Inorganic phosphate (Pi) homeostasis plays an important role in plant growth and abiotic stress tolerance. Several MYB-CC transcription factors involved in Pi homeostasis have been identified in rice (Oryza sativa). PHOSPHATE STARVATION RESPONSE-LIKE 7 (PHL7) is a class II MYC-CC protein, in which the MYC-CC domain is located at the N terminus. In this study, we established that OsPHL7 is localized to the nucleus and that the encoding gene is induced by Pi deficiency. The Pi-responsive genes and Pi transporter genes are positively regulated by OsPHL7. The overexpression of OsPHL7 enhanced the tolerance of rice plants to Pi starvation, whereas the RNA interference-based knockdown of this gene resulted in increased sensitivity to Pi deficiency. Transgenic rice plants overexpressing OsPHL7 produced more roots than wild-type plants under both Pi-sufficient and Pi-deficient conditions and accumulated more Pi in the shoots and roots. In addition, the overexpression of OsPHL7 enhanced rice tolerance to salt stress. Together, these results demonstrate that OsPHL7 is involved in the maintenance of Pi homeostasis and enhances tolerance to Pi deficiency and salt stress in rice.

Saving water under water deficit conditions by application of Xyway LFR@FMC: Greenhouse studies

Triazole fungicides are often referred to as "stress protectants" due to their ability to enhance the abiotic stress tolerance of plants. Xyway LFR@FMC (flutriafol) is a triazole and at-plant applied fungicide. The Xyway LFR@FMC fungicide that has been introduced into corn production system starting 2020 have been observed to improve plant performance under drought stress conditions. In this study, we accessed the potential of Xyway LFR@FMC product in altering the ability of corn (Zea mays L.) plants to control transpiration rates under water deficit-stressed (DS) conditions. Plants were grown under greenhouse conditions treated with Xyway LFR@FMC at 0.56, 0.77, and 1.11 L ha−1 in experiment 1 and 1.11 and 1.26 L ha−1 rates in experiment 2. Plants treated with 1.11 L ha−1 reduced the amount of water loss in response to DS and had the highest fraction of transpirable soil water (FTSW) thresholds. There was an increase in shoot hydraulic conductance (Kshoot) by 1.11 L ha−1 in both experiments. Plants treated with 0.77 and 1.11 L ha−1 had higher LWP rates compared to other treatments under DS conditions. In conclusion, the most likely chemical ingredient in Xyway LFR@FMC fungicide triggering the transpiration control response was flutriafol. This is the first report that early stomatal closure under soil drying conditions can be induced by the application of Xyway LFR@FMC fungicide. Application of at-plant fungicide, Xyway LFR@FMC has potential to reduce the negative effect of water-deficit stress in corn along with improving plants growth and physiological performance.

An Insight into the Role of Phenolics in Abiotic Stress Tolerance in Plants: Current Perspective for Sustainable Environment

Phenolic compounds (PCs) are a prominent class of secondary metabolites produced by plants and are essential for the natural role of the entire plant life cycle. PCs are formed in plants under both favorable and unfavorable conditions and have essential functions in signaling pathways, such as cell division, nutrient mineralization, hormone control, and reproduction. Under abiotic stress conditions, plants produce more polyphenols, which aid them in adapting to their environment. The phenylpropanoid biosynthetic pathway is activated under various environmental stress conditions, such as drought, heavy metal toxicity, salinity, and high/low temperatures, resulting in the deposition of compounds. These compounds can neutralize reactive oxygen species (ROS) produced in excessive amounts in crops under stressful conditions and adversely affect plants. It is imperative to investigate the functions of PCs in response to several abiotic stresses, as the phenylpropanoid pathway plays a crucial role in the metabolic pathway in crop plants, leading to the biosynthesis of a wide range of PCs. These compounds play various roles in plant growth, development, and response to environmental stress. Therefore, this review provides a comprehensive understanding of PCs and their exchanges with other cellular components, which is crucial for harnessing their potential to improve crop resilience to environmental stresses.

Exploring strigolactones for inducing abiotic stress tolerance in plants

Exploring strigolactones for inducing abiotic stress tolerance in plants

Transformation of SNAC1 under Stress Inducible Promoter Rd29a Confers High Yield and Stress Tolerance in Rice

Abiotic stress tolerance in plants is often induced by activation of transcription factors. An increased stress tolerance was observed in indica rice cultivar BRRI dhan55 after transforming with the transcription factor SNAC1 (stress responsive NAC1) under stress inducible promoter rd29A that minimized unexpected phenotype and metabolic burden in transgenic lines. Tissue culture independent Agrobacterium-mediated in planta transformation method was used. Molecular analyses confirmed the successful integration of the SNAC1 gene and significantly higher gene expression level in the transgenic lines. The transgenic lines showed 3:1 segregation ratio at T2 generation following the Mendelian law of inheritance. Assays for leaf disk senescence and chlorophyll content at 100 mM and 200 mM salt and survival rates at 200 mM salt and drought conditions at 12 days of water withdrawal and after recovery under water showed significantly increased stress tolerance in the transgenics lines at seedling stage compared to the wild type. Enhanced yield, spikelet fertility, and 100 grain weight were observed at the reproductive stage compared to wild type under both salinity and drought stress conditions. Thus, SNAC1 expression in plants under inducible promoter is a better choice to enhance stress tolerance and yield under salinity and drought conditions. Plant Tissue Cult. & Biotech. 33(2): 115-133, 2023 (December)

Karrikin signalling: impacts on plant development and abiotic stress tolerance.

Plants rely upon a diverse range of metabolites to control growth and development, and to overcome stress that results from suboptimal conditions. Karrikins (KARs) are a class of butenolide compounds found in smoke that stimulate seed germination and regulate various developmental processes in plants. KARs are perceived via a plant α/β-hydrolase called KARRIKIN INSENSITIVE2 (KAI2), which also functions as a receptor for a postulated phytohormone, provisionally termed KAI2 ligand (KL). Considered natural analogues of KL, KARs have been extensively studied for their effects on plant growth and their crosstalk with plant hormones. The perception and response pathway for KAR-KL signalling is closely related to that of strigolactones, another class of butenolides with numerous functions in regulating plant growth. KAR-KL signalling influences seed germination, seedling photomorphogenesis, root system architecture, abiotic stress responses, and arbuscular mycorrhizal symbiosis. Here, we summarize current knowledge of KAR-KL signalling, focusing on its role in plant development, its effects on stress tolerance, and its interaction with other signalling mechanisms.

Post-Translational Modifications in Histones and Their Role in Abiotic Stress Tolerance in Plants.

Abiotic stresses profoundly alter plant growth and development, resulting in yield losses. Plants have evolved adaptive mechanisms to combat these challenges, triggering intricate molecular responses to maintain tissue hydration and temperature stability during stress. A pivotal player in this defense is histone modification, governing gene expression in response to diverse environmental cues. Post-translational modifications (PTMs) of histone tails, including acetylation, phosphorylation, methylation, ubiquitination, and sumoylation, regulate transcription, DNA processes, and stress-related traits. This review comprehensively explores the world of PTMs of histones in plants and their vital role in imparting various abiotic stress tolerance in plants. Techniques, like chromatin immune precipitation (ChIP), ChIP-qPCR, mass spectrometry, and Cleavage Under Targets and Tag mentation, have unveiled the dynamic histone modification landscape within plant cells. The significance of PTMs in enhancing the plants' ability to cope with abiotic stresses has also been discussed. Recent advances in PTM research shed light on the molecular basis of stress tolerance in plants. Understanding the intricate proteome complexity due to various proteoforms/protein variants is a challenging task, but emerging single-cell resolution techniques may help to address such challenges. The review provides the future prospects aimed at harnessing the full potential of PTMs for improved plant responses under changing climate change.

Streptomyces alleviate abiotic stress in plant by producing pteridic acids

Soil microbiota can confer fitness advantages to plants and increase crop resilience to drought and other abiotic stressors. However, there is little evidence on the mechanisms correlating a microbial trait with plant abiotic stress tolerance. Here, we report that Streptomyces effectively alleviate drought and salinity stress by producing spiroketal polyketide pteridic acid H (1) and its isomer F (2), both of which promote root growth in Arabidopsis at a concentration of 1.3 nM under abiotic stress. Transcriptomics profiles show increased expression of multiple stress responsive genes in Arabidopsis seedlings after pteridic acids treatment. We confirm in vivo a bifunctional biosynthetic gene cluster for pteridic acids and antimicrobial elaiophylin production. We propose it is mainly disseminated by vertical transmission and is geographically distributed in various environments. This discovery reveals a perspective for understanding plant-Streptomyces interactions and provides a promising approach for utilising beneficial Streptomyces and their secondary metabolites in agriculture to mitigate the detrimental effects of climate change.

Cerium oxide as a nanozyme for plant abiotic stress tolerance: An overview of the mechanisms

Abiotic stress in plants is considered an important environmental constraint that ultimately reduces agricultural production. Nanotechnology is an advancing technology for improving plant growth and mitigating stress factors in modern agriculture. Cerium oxide, a rare lanthanide in Earth’s crust, holds significant potential in various industrial sectors. Research on engineered cerium oxide nanoparticles has been proven to play a significant role in promoting plant growth and alleviating environmental stress factors at lower dosage levels. The accumulation of cerium oxide nanoparticles benefits plants by improving morphological attributes, antioxidants, and photosynthetic parameters. Application of cerium oxide nanoparticles as nanozymes under abiotic stress conditions activates stress signaling cascades in plants to scavenge the reactive oxygen species (ROS) generated. However, higher dosages can lead to toxicological effects in plants. Higher accumulation of cerium oxide nanoparticles in different plant tissues is critical for reviewing their interference with the food chain and safety. This review covers the impact of cerium oxide nanoparticles on plant performance, abiotic stress tolerance, and the underlying mechanisms when interacting with plants.

The Utilization of Seed Priming as a Tool to Overcome Salt and Drought Stresses: Is Still a Long Way to Go?

Abiotic stresses, sometimes due to dramatic environmental changes, such as sudden and heavy rainfalls, or drought, increasing temperatures or soil salinization, deeply affect the growth and yield of plants. Progress in terms of improving the abiotic stress tolerance of plants can be obtained via classical breeding and genetic engineering, which can be slow, or by practice, such as acclimation and seed priming. The latter can improve seedling performance, and it can be considered a short-term approach. Seed priming with different agents and biopriming may offer the possibility to improve stress tolerance, even though its beneficial effect depends on crop species, dose, and time of application. The aim of this review is to highlight some of the current research trends that may ultimately lead to strategies for stress-proofing crop species. The focus is on those abiotic stresses, e.g., drought and soil salinity, that are most often associated with climate change and poor agricultural practices and those crops that are most important for human nutrition. Comments are provided on the challenges and pros and cons of this methodology.

Identification of rice melatonin receptor OsPMTR and its comparative in silico analysis with arabidopsis AtCAND2 receptor

Melatonin (N-acetyl-5-methoxytryptamine) is a signaling molecule having crucial role in plant growth, development and stress responses. Melatonin receptor has been identified in Arabidopsis, maize, tobacco and cassava. However no bona fide receptor has been identified in rice. Here we have identified a homolog of Arabidopsis melatonin receptor (AtCAND2/PMTR1) in rice OsPMTR. It is predicted to be a plasma membrane localized, seven transmembrane domain containing protein resembling G-protein coupled receptor. The comparative in silico analysis revealed that OsPMTR has similar gene structure and physiochemical properties as that of AtCAND2/PMTR1. Molecular docking analysis of OsPMTR and melatonin revealed pKi and ligand efficiency that were comparable to that of AtCAD2 which indicates strong possible interaction between OsPMTR and melatonin. To further elucidate melatonin signaling, we identified 24 potential interacting partners of OsPMTR using in silico protein-protein interaction, and also identified co-expression network of OsPMTR. OsRGA1, a known downstream signaling protein in G-protein mediated pathway, was identified as one of the interacting partners. We confirmed the interaction of OsPMTR with OsRGA1 through molecular docking. The quantitative expression analysis revealed that OsPMTR, two interacting partners (OsRGA1, OsCOLD1) and four co-expressed genes (OsTGA2.1, OsWRKY90, OsDREB6/OsERF60 and OsTCP5) were significantly induced by exogenous melatonin treatment in rice. This further suggests a potential role of OsPMTR interacting partners and coexpressed genes in OsPMTR signaling pathway. Our study shows that OsPMTR may act as a G-protein coupled receptor (GPCR) which activates the G-protein signaling through the downstream α subunit (OsRGA1) and may transcriptionally regulate many transcription factors and genes related to plant growth, development, biotic and abiotic stress tolerance. Our findings lay the foundation for the future experimental investigation in plant system to bring out the functional role of OsPMTR as a melatonin receptor and its signaling pathway in rice. This will further help develop cheap agonists and orthogonal receptors for management of abiotic stress tolerance and yield of crops. © 2017 Elsevier Inc. All rights reserved.

IbMYB73 targets abscisic acid-responsive IbGER5 to regulate root growth and stress tolerance in sweet potato.

Root development influences plant responses to environmental conditions, and well-developed rooting enhances plant survival under abiotic stress. However, the molecular and genetic mechanisms underlying root development and abiotic stress tolerance in plants remain unclear. In this study, we identified the MYB transcription factor-encoding gene IbMYB73 by cDNA-amplified fragment length polymorphism and RNA-seq analyses. IbMYB73 expression was greatly suppressed under abiotic stress in the roots of the salt-tolerant sweet potato (Ipomoea batatas) line ND98, and its promoter activity in roots was significantly reduced by abscisic acid (ABA), NaCl, and mannitol treatments. Overexpression of IbMYB73 significantly inhibited adventitious root growth and abiotic stress tolerance, whereas IbMYB73-RNAi plants displayed the opposite pattern. IbMYB73 influenced the transcription of genes involved in the ABA pathway. Furthermore, IbMYB73 formed homodimers and activated the transcription of ABA-responsive protein IbGER5 by binding to an MYB binding sites I motif in its promoter. IbGER5 overexpression significantly inhibited adventitious root growth and abiotic stress tolerance concomitantly with a reduction in ABA content, while IbGER5-RNAi plants showed the opposite effect. Collectively, our results demonstrated that the IbMYB73-IbGER5 module regulates ABA-dependent adventitious root growth and abiotic stress tolerance in sweet potato, which provides candidate genes for the development of elite crop varieties with well-developed root-mediated abiotic stress tolerance.

Flavonols affect the interrelated glucosinolate and camalexin biosynthetic pathways in Arabidopsis thaliana.

Flavonols are structurally and functionally diverse biomolecules involved in plant biotic and abiotic stress tolerance, pollen development, and inhibition of auxin transport. However, their effects on global gene expression and signaling pathways are unclear. To explore the roles of flavonol metabolites in signaling, we performed comparative transcriptome and targeted metabolite profiling of seedlings from the flavonol-deficient Arabidopsis loss-of-function mutant flavonol synthase1 (fls1) with and without exogenous supplementation of flavonol derivatives (kaempferol, quercetin, and rutin). RNA-seq results indicated that flavonols modulate various biological and metabolic pathways, with significant alterations in camalexin and aliphatic glucosinolate synthesis. Flavonols negatively regulated camalexin biosynthesis but appeared to promote the accumulation of aliphatic glucosinolates via transcription factor-mediated up-regulation of biosynthesis genes. Interestingly, upstream amino acid biosynthesis genes involved in methionine and tryptophan synthesis were altered under flavonol deficiency and exogenous supplementation. Quercetin treatment significantly up-regulated aliphatic glucosinolate biosynthesis genes compared with kaempferol and rutin. In addition, expression and metabolite analysis of the transparent testa7 mutant, which lacks hydroxylated flavonol derivatives, clarified the role of quercetin in the glucosinolate biosynthesis pathway. This study elucidates the molecular mechanisms by which flavonols interfere with signaling pathways, their molecular targets, and the multiple biological activities of flavonols in plants.