Expression Analyses of Soybean VOZ Transcription Factors and the Role of GmVOZ1G in Drought and Salt Stress Tolerance

GhVOZ1-AVP1 module positively regulates salt tolerance in upland cotton (Gossypium hirsutum L.)

Vascular Plant One‑zinc Finger (VOZ) transcription factor can respond to a variety of abiotic stresses, however its function in cotton and the molecular mechanisms of response to salt tolerance remained unclear. In this study, we found that GhVOZ1 is highly expressed in stamen and stem of cotton under normal conditions. The expression of GhVOZ1 increased significantly after 3 h of salt treatment in three-leaf staged upland cotton. Overexpressed transgenic lines of GhVOZ1 in Arabidopsis and upland cotton were treated with salt stress and we found that GhVOZ1 could respond positively to salt stress. GhVOZ1 can regulate Arabidopsis Vacuolar Proton Pump Pyrophosphatase (H+-PPase) gene (AVP1) expression through specific binding to GCGTCTAAAGTACGC site on GhAVP1 promoter, which was examined through Dual-luciferase assay and Electrophoretic mobility shift assay (EMSA). AVP1 expression was significantly increased in Arabidopsis with GhVOZ1 overexpression, while GhAVP1 expression was decreased in virus induced gene silenced (VIGS) cotton plants of GhVOZ1. Knockdown of GhAVP1 expression in cotton plants by VIGS showed decreased superoxide dismutase (SOD) and peroxidase (POD) activities, whereas an increased malondialdehyde (MDA) content and ultimately decreased salt tolerance. The GhVOZ1-AVP1 module could maintain sodium ion homeostasis through cell ion transport and positively regulate the salt tolerance in cotton, providing new ideas and insights for the study of salt tolerance.

H2O2-dependent oxidation of the transcription factor GmNTL1 promotes salt tolerance in soybean

Reactive oxygen species (ROS) play an essential role in plant growth and responses to environmental stresses. Plant cells sense and transduce ROS signaling directly via hydrogen peroxide (H2O2)-mediated posttranslational modifications (PTMs) on protein cysteine residues. Here, we show that the H2O2-mediated cysteine oxidation of NAC WITH TRANS-MEMBRANE MOTIF1-LIKE 1 (GmNTL1) in soybean (Glycine max) during salt stress promotes its release from the endoplasmic reticulum (ER) membrane and translocation to the nucleus. We further show that an oxidative posttranslational modification on GmNTL1 residue Cys-247 steers downstream amplification of ROS production by binding to and activating the promoters of RESPIRATORY BURST OXIDASE HOMOLOG B (GmRbohB) genes, thereby creating a feed-forward loop to fine-tune GmNTL1 activity. In addition, oxidation of GmNTL1 Cys-247 directly promotes the expression of CATION H+ EXCHANGER 1 (GmCHX1)/SALT TOLERANCE-ASSOCIATED GENE ON CHROMOSOME 3 (GmSALT3) and Na+/H+ Antiporter 1 (GmNHX1). Accordingly, transgenic overexpression of GmNTL1 in soybean increases the H2O2 levels and K+/Na+ ratio in the cell, promotes salt tolerance, and increases yield under salt stress, while an RNA interference-mediated knockdown of GmNTL1 elicits the opposite effects. Our results reveal that the salt-induced oxidation of GmNTL1 promotes its relocation and transcriptional activity through an H2O2-mediated posttranslational modification on cysteine that improves resilience of soybean against salt stress.

Subcellular Proteomics to Elucidate Soybean Response to Abiotic Stress

Climate change jeopardizes soybean production by declining seed yield and quality. In this review, the morphophysiological alterations of soybean in response to abiotic stress are summarized, followed by illustrations of cellular metabolisms and regulatory mechanisms to organellar stress based on subcellular proteomics. This highlights the communications associated with reactive oxygen species scavenging, molecular chaperones, and phytohormone signals among subcellular compartments. Given the complexity of climate change and the limitations of plants in coping with multiple abiotic stresses, a generic response to environmental constraints is proposed between calcium and abscisic acid signals in subcellular organelles. This review summarizes the findings of subcellular proteomics in stressed soybean and discusses the future prospects of subcellular proteomics for promoting the improvement of climate-tolerant crops.

Twenty years of mining salt tolerance genes in soybean

Current combined challenges of rising food demand, climate change and farmland degradation exert enormous pressure on agricultural production. Worldwide soil salinization, in particular, necessitates the development of salt-tolerant crops. Soybean, being a globally important produce, has its genetic resources increasingly examined to facilitate crop improvement based on functional genomics. In response to the multifaceted physiological challenge that salt stress imposes, soybean has evolved an array of defences against salinity. These include maintaining cell homeostasis by ion transportation, osmoregulation, and restoring oxidative balance. Other adaptations include cell wall alterations, transcriptomic reprogramming, and efficient signal transduction for detecting and responding to salt stress. Here, we reviewed functionally verified genes that underly different salt tolerance mechanisms employed by soybean in the past two decades, and discussed the strategy in selecting salt tolerance genes for crop improvement. Future studies could adopt an integrated multi-omic approach in characterizing soybean salt tolerance adaptations and put our existing knowledge into practice via omic-assisted breeding and gene editing. This review serves as a guide and inspiration for crop developers in enhancing soybean tolerance against abiotic stresses, thereby fulfilling the role of science in solving real-life problems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01383-3.

Molecular characterization of Satsuma mandarin (Citrus unshiu Marc.) VASCULAR PLANT ONE-ZINC FINGER2 (CuVOZ2) interacting with CuFT1 and CuFT3

Shortening the juvenility is a burning issue in breeding fruit trees such as Satsuma mandarin (Citrus unshiu Marc.). Decreasing the breeding period requires a comprehensive understanding of the flowering process in woody plants. Throughout the Arabidopsis flowering system, FLOWERING LOCUS T (FT) interacts with other transcription factors (TFs) and functions as a transmissible floral inducer. In a previous study, a VASCULAR PLANT ONE-ZINC FINGER1 (VOZ1)-like TF from the Satsuma mandarin, CuVOZ1, showed protein-protein interaction with two citrus FTs in a yeast two-hybrid (Y2H) system and precocious flowering in Arabidopsis. In this study, another VOZ, CuVOZ2, was isolated from the Satsuma mandarin 'Aoshima' and protein-protein interaction was confirmed between CuVOZ2 and CuFTs. No apical meristem (NAM) and zinc coordination motifs were identified within the N-terminal of CuVOZ2. Docking simulation predicted that interactions between CuVOZ2 and CuFTs might occur in domain B of CuVOZ2, which contains a zinc finger motif. According to docking predictions, the distances between the amino acid residues involved ranged from 1.09 to 4.37 Å, indicating weak Van der Waals forces in the interaction. Cys216, Cys221, Cys235, and His239 in CuVOZ2 were suggested to bond with a Zn2+ in the Zn coordination motif. Ectopic expression of 35SΩ:CuVOZ2 in Arabidopsis affected the flowering time, length of inflorescence and internode, and number of siliques, suggesting that CuVOZ2 might regulate both vegetative and reproductive development, act as a trigger for early flowering, and be involved in the elongation of inflorescence possibly in a slightly different way than CuVOZ1.

Genome-Wide Analysis and Expression Profiles of the VOZ Gene Family in Quinoa (Chenopodium quinoa)

Vascular plant one zinc-finger (VOZ) proteins are a plant-specific transcription factor family and play important roles in plant development and stress responses. However, little is known about the VOZ genes in quinoa. In the present study, a genome-wide investigation of the VOZ gene family in quinoa was performed, including gene structures, conserved motifs, phylogeny, and expression profiles. A total of four quinoa VOZ genes distributed on three chromosomes were identified. Based on phylogenetic analysis, CqVOZ1 and CqVOZ3 belong to subfamily II, and CqVOZ2 and CqVOZ4 belong to subfamily III. Furthermore, the VOZ transcription factors of quinoa and sugarbeet were more closely related than other species. Except for CqVOZ3, all the other three CqVOZs have four exons and four introns. Analysis of conserved motifs indicated that each CqVOZ member contained seven common motifs. Multiple sequence alignment showed that the CqVOZ genes were highly conserved with consensus sequences, which might be plausibly significant for the preservation of structural integrity of the family proteins. Tissue expression analysis revealed that four CqVOZ genes were highly expressed in inflorescence and relatively low in leaves and stems, suggesting that these genes had obvious tissue expression specificity. The expression profiles of the quinoa CqVOZs under various abiotic stresses demonstrated that these genes were differentially induced by cold stress, salt stress, and drought stress. The transcript level of CqVOZ1 and CqVOZ4 were down-regulated by salt stress and drought stress, while CqVOZ2 and CqVOZ3 were up-regulated by cold, salt, and drought stress, which could be used as abiotic stress resistance candidate genes. This study systematically identifies the CqVOZ genes at the genome-wide level, contributing to a better understanding of the quinoa VOZ transcription factor family and laying a foundation for further exploring the molecular mechanism of development and stress resistance of quinoa.

Physiological and comparative transcriptome analyses reveal the mechanisms underlying waterlogging tolerance in a rapeseed anthocyanin-more mutant

Background

Rapeseed (Brassica napus) is the second largest oil crop worldwide. It is widely used in food, energy production and the chemical industry, as well as being an ornamental. Consequently, it has a large economic value and developmental potential. Waterlogging is an important abiotic stress that restricts plant growth and development. However, little is known about the molecular mechanisms underlying waterlogging tolerance in B. napus.

Results

In the present study, the physiological changes and transcriptomes of germination-stage rapeseed in response to waterlogging stress were investigated in the B. napus cultivar ‘Zhongshuang 11’ (ZS11) and its anthocyanin-more (am) mutant, which was identified in our previous study. The mutant showed stronger waterlogging tolerance compared with ZS11, and waterlogging stress significantly increased anthocyanin, soluble sugar and malondialdehyde contents and decreased chlorophyll contents in the mutant after 12 days of waterlogging. An RNA-seq analysis identified 1370 and 2336 differently expressed genes (DEGs) responding to waterlogging stress in ZS11 and am, respectively. An enrichment analysis revealed that the DEGs in ZS11 were predominately involved in carbohydrate metabolism, whereas those in the am mutant were particularly enriched in plant hormone signal transduction and response to endogenous stimulation. In total, 299 DEGs were identified as anthocyanin biosynthesis-related structural genes (24) and regulatory genes encoding transcription factors (275), which may explain the increased anthocyanin content in the am mutant. A total of 110 genes clustered in the plant hormone signal transduction pathway were also identified as DEGs, including 70 involved in auxin and ethylene signal transduction that were significantly changed in the mutant. Furthermore, the expression levels of 16 DEGs with putative roles in anthocyanin accumulation and biotic/abiotic stress responses were validated by quantitative real-time PCR as being consistent with the transcriptome profiles.

Conclusion

This study provides new insights into the molecular mechanisms of increased anthocyanin contents in rapeseed in response to waterlogging stress, which should be useful for reducing the damage caused by waterlogging stress and for further breeding new rapeseed varieties with high waterlogging tolerance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02155-5.

Identification of Known and Novel Arundo donax L. MicroRNAs and Their Targets Using High-Throughput Sequencing and Degradome Analysis

MicroRNAs (miRNAs) are a class of non-coding molecules involved in the regulation of a variety of biological processes. They have been identified and characterized in several plant species, but only limited data are available for Arundo donax L., one of the most promising bioenergy crops. Here we identified, for the first time, A. donax conserved and novel miRNAs together with their targets, through a combined analysis of high-throughput sequencing of small RNAs, transcriptome and degradome data. A total of 134 conserved miRNAs, belonging to 45 families, and 27 novel miRNA candidates were identified, along with the corresponding primary and precursor miRNA sequences. A total of 96 targets, 69 for known miRNAs and 27 for novel miRNA candidates, were also identified by degradome analysis and selected slice sites were validated by 5′-RACE. The identified set of conserved and novel candidate miRNAs, together with their targets, extends our knowledge about miRNAs in monocots and pave the way to further investigations on miRNAs-mediated regulatory processes in A. donax, Poaceae and other bioenergy crops.

Genome-Wide Identification of the AP2/ERF Gene Family and Functional Analysis of GmAP2/ERF144 for Drought Tolerance in Soybean

Drought is a major environmental constraint that causes substantial reductions in plant growth and yield. Expression of stress-related genes is largely regulated by transcription factors (TFs), including in soybean [Glycine max (L.) Merr.]. In this study, 301 GmAP2/ERF genes that encode TFs were identified in the soybean genome. The TFs were divided into five categories according to their homology. Results of previous studies were then used to select the target gene GmAP2/ERF144 from among those up-regulated by drought and salt stress in the transcriptome. According to respective tissue expression analysis and subcellular determination, the gene was highly expressed in leaves and encoded a nuclear-localized protein. To validate the function of GmAP2/ERF144, the gene was overexpressed in soybean using Agrobacterium-mediated transformation. Compared with wild-type soybean, drought resistance of overexpression lines increased significantly. Under drought treatment, leaf relative water content was significantly higher in overexpressed lines than in the wild-type genotype, whereas malondialdehyde content and electrical conductivity were significantly lower than those in the wild type. Thus, drought resistance of transgenic soybean increased with overexpression of GmAP2/ERF144. To understand overall function of the gene, network analysis was used to predict the genes that interacted with GmAP2/ERF144. Reverse-transcription quantitative PCR showed that expression of those interacting genes in two transgenic lines was 3 to 30 times higher than that in the wild type. Therefore, GmAP2/ERF144 likely interacted with those genes; however, that conclusion needs to be verified in further specific experiments.

Characterization of Vascular plant One-Zinc finger (VOZ) in soybean (Glycine max and Glycine soja) and their expression analyses under drought condition

Vascular plant one-zinc-finger (VOZ) transcription factors regulate plant growth and development under drought conditions. Six VOZ transcription factors encoding genes exist in soybean genome (both in Glycine max and Glycine soja). Herein, GmVOZs and GsVOZs were identified through in silico analysis and characterized with different bioinformatics tools and expression analysis. Phylogenetic analysis classified VOZ genes in four groups. Sequence logos analysis among G. max and G. soja amino acid residues revealed higher conservation. Presence of stress related cis-elements in the upstream regions of GmVOZs and GsVOZs highlights their role in tolerance against abiotic stresses. The collinearity analysis identified 14 paralogous/orthologous gene pairs within and between G. max and G. soja. The Ka/Ks values showed that soybean VOZ genes underwent selection pressure with limited functional deviation arising from whole genome and segmental duplication. The GmVOZs and GsVOZs were found to express in roots and leaves at seedling stage. The qRT-PCR revealed that GmVOZs and GsVOZs transcripts can be regulated by abiotic stresses such as polyethylene glycol (PEG). The findings of this study will provide a reference to decipher physiological and molecular functions of VOZ genes in soybean.

Genome-Wide Identification and Characterization of TALE Superfamily Genes in Soybean (Glycine max L.)

The three-amino-acid-loop-extension (TALE) superfamily genes broadly existed in plants, which played important roles in plant growth, development and abiotic stress responses. In this study, we identified 68 Glycine max TALE (GmTALE) superfamily members. Phylogenetic analysis divided the GmTALE superfamily into the BEL1-like (BLH/BELL homeodomain) and the KNOX (KNOTTED-like homeodomain) subfamilies. Moreover, the KNOX subfamily could be further categorized into three clades (KNOX Class I, KNOX Class II and KNOX Class III). The GmTALE genes showed similarities in the gene structures in the same subfamily or clade, whose coding proteins exhibited analogous motif and conserved domain compositions. Besides, synteny analyses and evolutionary constraint evaluations of the TALE members among soybean and different species provided more clues for GmTALE superfamily evolution. The cis-element analyses in gene promoter regions and relevant gene expression profiling revealed different regulating roles of GmTALE genes during soybean plant development, saline and dehydration stresses. Genome-wide characterization, evolution, and expression profile analyses of GmTALE genes can pave the way for future gene functional research and facilitate their roles for applications in genetic improvement on soybean in saline and dehydration stresses.

Ion homeostasis for salinity tolerance in plants: a molecular approach

Soil salinity is one of the major environmental stresses faced by the plants. Sodium chloride is the most important salt responsible for inducing salt stress by disrupting the osmotic potential. Due to various innate mechanisms, plants adapt to the sodic niche around them. Genes and transcription factors regulating ion transport and exclusion such as salt overly sensitive (SOS), Na⁺ /H⁺ exchangers (NHXs), high sodium affinity transporter (HKT) and plasma membrane protein (PMP) are activated during salinity stress and help in alleviating cells of ion toxicity. For salt tolerance in plants signal transduction and gene expression is regulated via transcription factors such as NAM (no apical meristem), ATAF (Arabidopsis transcription activation factor), CUC (cup-shaped cotyledon), Apetala 2/ethylene responsive factor (AP2/ERF), W-box binding factor (WRKY) and basic leucine zipper domain (bZIP). Cross-talk between all these transcription factors and genes aid in developing the tolerance mechanisms adopted by plants against salt stress. These genes and transcription factors regulate the movement of ions out of the cells by opening various membrane ion channels. Mutants or knockouts of all these genes are known to be less salt-tolerant compared to wild-types. Using novel molecular techniques such as analysis of genome, transcriptome, ionome and metabolome of a plant, can help in expanding the understanding of salt tolerance mechanism in plants. In this review, we discuss the genes responsible for imparting salt tolerance under salinity stress through transport dynamics of ion balance and need to integrate high-throughput molecular biology techniques to delineate the issue.

Evolution and Stress Responses of CLO Genes and Potential Function of the GhCLO06 Gene in Salt Resistance of Cotton

The caleosin (CLO) protein family displays calcium-binding properties and plays an important role in the abiotic stress response. Here, a total of 107 CLO genes were identified in 15 plant species, while no CLO genes were detected in two green algal species. Evolutionary analysis revealed that the CLO gene family may have evolved mainly in terrestrial plants and that biological functional differentiation between species and functional expansion within species have occurred. Of these, 56 CLO genes were identified in four cotton species. Collinearity analysis showed that CLO gene family expansion mainly occurred through segmental duplication and whole-genome duplication in cotton. Sequence alignment and phylogenetic analysis showed that the CLO proteins of the four cotton species were mainly divided into two types: H-caleosins (class I) and L-caleosins (class II). Cis-acting element analysis and quantitative RT-PCR (qRT-PCR) suggested that GhCLOs might be regulated by abscisic acid (ABA) and methyl jasmonate (MeJA). Moreover, transcriptome data and qRT-PCR results revealed that GhCLO genes responded to salt and drought stresses. Under salt stress, gene-silenced plants (TRV: GhCLO06) showed obvious yellowing and wilting, higher malondialdehyde (MDA) content accumulation, and significantly lower activities of superoxide dismutase (SOD) and peroxidase (POD), indicating that GhCLO06 plays a positive regulatory role in cotton salt tolerance. In gene-silenced plants (TRV: GhCLO06), ABA-related genes (GhABF2, GhABI5, and GhNAC4) were significantly upregulated after salt stress, suggesting that the regulation of salt tolerance may be related to the ABA signaling pathway. This research provides an important reference for further understanding and analyzing the molecular regulatory mechanism of CLOs for salt tolerance.