RNA-Seq Reveals Waterlogging-Triggered Root Plasticity in Mungbean Associated with Ethylene and Jasmonic Acid Signal Integrators for Root Regeneration

Genome-wide identification of CAMTA genes and their expression dependence on light and calcium signaling during seedling growth and development in mung bean

BACKGROUND

Calmodulin-binding transcription activator (CAMTA) is comprised of a group of transcription factors and plays an important role in the Ca2+ signaling pathway, mediating various molecular responses via interactions with other transcription factors and binding to the promoter region of specific genes. Mung beans (Vigna radiata) are one of the most commonly consumed commodities in Asia. To date, CAMTA proteins have not been characterized in this important crop plant.

RESULTS

Eight paralogous VrCAMTA genes were identified and found to be distributed on five of the 11 chromosomes. The proteins possessed CG-1 DNA-binding domains with bipartite NLS signals, ankyrin domains, CaM-binding IQ motifs, and CaM-binding domain (CaMBD). The 2 kb upstream regions of VrCAMTA genes contained sequence motifs of abscisic acid-responsive elements (ABRE) and ethylene-responsive elements (ERE), and binding sites for transcription factors of the bZIP and bHLH domains. Analysis of RNA-seq data from a public repository revealed ubiquitous expression of the VrCAMTA genes, as VrCAMTA1 was expressed at the highest level in seedling leaves, whereas VrCAMTA8 was expressed at the lowest level, which agreed with the RT-qPCR analysis performed on the first true leaves. On day four after leaf emergence, all VrCAMTA genes were upregulated, with VrCAMTA1 exhibiting the highest degree of upregulation. In darkness on day 4, upregulation was not observed in most VrCAMTA genes, except VrCAMTA7, for which a low degree of upregulation was found, whereas no difference was found in VrCAMTA8 expression between light and dark conditions. Treatment with calcium ionophores enhanced VrCAMTA expression under light and/or dark conditions at different times after leaf emergence, suggesting that calcium signaling is involved in the light-induced upregulation of VrCAMTA gene expression.

CONCLUSIONS

The expression dependence of nearly all VrCAMTA genes on light and calcium signaling suggests their possible differential but likely complementary roles during the early stages of mung bean growth and development.

Analysis of Auxin-Encoding Gene Family in Vigna radiata and It's Cross-Species Expression Modulating Waterlogging Tolerance in Wild Vigna umbellata

Mungbean is known to be susceptible to waterlogging (WL) stress. Some of the wild species have the potential to tolerate this through various physiological and molecular mechanisms. Auxin Response Factor (ARF) and Auxin/Indole Acetic Acid (AUX/IAA), an early responsive gene family, has multiple functions in growth, development, and stress tolerance. Here, we report the first comprehensive analysis of the ARF and AUX/IAA gene family in mungbean. A total of 26 ARF and 19 AUX/IAA genes were identified from the mungbean genome. The ARF and AUX/IAA candidates were clearly grouped into two major clades. Further, the subgrouping within the major clades indicated the presence of significant diversity. The gene structure, motif analysis, and protein characterization provided the clue for further fundamental research. Out of the10 selected candidate genes, VrARF-5, VrARF-11, VrARF-25, and VrAUX/IAA-9 were found to significantly multiple-fold gene expression in the hypocotyl region of WL-tolerant wild relatives (PRR 2008-2) provides new insight into a role in the induction of lateral root formation under WL stress. The analysis provides an insight into the structural diversity of ARF and AUX/IAA genes in mungbean. These results increase our understanding of ARF and AUX/IAA genes and therefore offer robust information for functional investigations, which can be taken up in the future and will form a foundation for improving tolerance against waterlogging stress.

Elucidating the molecular responses to waterlogging stress in onion (Allium cepa L.) leaf by comparative transcriptome profiling

Introduction

Waterlogging is a major stress that severely affects onion cultivation worldwide, and developing stress-tolerant varieties could be a valuable measure for overcoming its adverse effects. Gathering information regarding the molecular mechanisms and gene expression patterns of waterlogging-tolerant and sensitive genotypes is an effective method for improving stress tolerance in onions. To date, the waterlogging tolerance-governing molecular mechanism in onions is unknown.

Methods

This study identified the differentially expressed genes (DEGs) through transcriptome analysis in leaf tissue of two onion genotypes (Acc. 1666; tolerant and W-344; sensitive) presenting contrasting responses to waterlogging stress.

Results

Differential gene expression analysis revealed that in Acc. 1666, 1629 and 3271 genes were upregulated and downregulated, respectively. In W-344, 2134 and 1909 genes were upregulated and downregulated, respectively, under waterlogging stress. The proteins coded by these DEGs regulate several key biological processes to overcome waterlogging stress such as phytohormone production, antioxidant enzymes, programmed cell death, and energy production. The clusters of orthologous group pathway analysis revealed that DEGs contributed to the post-translational modification, energy production, and carbohydrate metabolism-related pathways under waterlogging stress. The enzyme assay demonstrated higher activity of antioxidant enzymes in Acc. 1666 than in W-344. The differential expression of waterlogging tolerance related genes, such as those related to antioxidant enzymes, phytohormone biosynthesis, carbohydrate metabolism, and transcriptional factors, suggested that significant fine reprogramming of gene expression occurs in response to waterlogging stress in onion. A few genes such as ADH, PDC, PEP carboxylase, WRKY22, and Respiratory burst oxidase D were exclusively upregulated in Acc. 1666.

Discussion

The molecular information about DEGs identified in the present study would be valuable for improving stress tolerance and for developing waterlogging tolerant onion varieties.

Design, execution, and interpretation of plant RNA-seq analyses

Genomics has transformed our understanding of the genetic architecture of traits and the genetic variation present in plants. Here, we present a review of how RNA-seq can be performed to tackle research challenges addressed by plant sciences. We discuss the importance of experimental design in RNA-seq, including considerations for sampling and replication, to avoid pitfalls and wasted resources. Approaches for processing RNA-seq data include quality control and counting features, and we describe common approaches and variations. Though differential gene expression analysis is the most common analysis of RNA-seq data, we review multiple methods for assessing gene expression, including detecting allele-specific gene expression and building co-expression networks. With the production of more RNA-seq data, strategies for integrating these data into genetic mapping pipelines is of increased interest. Finally, special considerations for RNA-seq analysis and interpretation in plants are needed, due to the high genome complexity common across plants. By incorporating informed decisions throughout an RNA-seq experiment, we can increase the knowledge gained.

Ethylene and Jasmonates Signaling Network Mediating Secondary Metabolites under Abiotic Stress

Plants are sessile organisms that face environmental threats throughout their life cycle, but increasing global warming poses an even more existential threat. Despite these unfavorable circumstances, plants try to adapt by developing a variety of strategies coordinated by plant hormones, resulting in a stress-specific phenotype. In this context, ethylene and jasmonates (JAs) present a fascinating case of synergism and antagonism. Here, Ethylene Insensitive 3/Ethylene Insensitive-Like Protein1 (EIN3/EIL1) and Jasmonate-Zim Domain (JAZs)-MYC2 of the ethylene and JAs signaling pathways, respectively, appear to act as nodes connecting multiple networks to regulate stress responses, including secondary metabolites. Secondary metabolites are multifunctional organic compounds that play crucial roles in stress acclimation of plants. Plants that exhibit high plasticity in their secondary metabolism, which allows them to generate near-infinite chemical diversity through structural and chemical modifications, are likely to have a selective and adaptive advantage, especially in the face of climate change challenges. In contrast, domestication of crop plants has resulted in change or even loss in diversity of phytochemicals, making them significantly more vulnerable to environmental stresses over time. For this reason, there is a need to advance our understanding of the underlying mechanisms by which plant hormones and secondary metabolites respond to abiotic stress. This knowledge may help to improve the adaptability and resilience of plants to changing climatic conditions without compromising yield and productivity. Our aim in this review was to provide a detailed overview of abiotic stress responses mediated by ethylene and JAs and their impact on secondary metabolites.

Transcriptomic and biochemical analyses of drought response mechanism in mung bean (Vignaradiata (L.) Wilczek) leaves

Drought is a major factor that limiting mung bean development. To clarify the molecular mechanism of mung bean in response to drought stress, 2 mung bean groups were established, the experimental group (drought-treated) and the control group (normal water management). With prominent difference of 2 groups in stomatal conductance, relative water content and phenotype, leaf samples were collected at 4 stages, and the physiological index of MDA, POD, chlorophyll, and soluble proteins were estimated. RNA-seq was used to obtain high quality data of samples, and differentially expressed genes were identified by DESeq2. With GO and KEGG analysis, DEGs were enriched into different classifications and pathways. WGCNA was used to detect the relationship between physiological traits and genes, and qPCR was performed to confirm the accuracy of the data. We obtained 169.49 Gb of clean data from 24 samples, and the Q30 of each date all exceeded 94%. In total, 8963 DEGs were identified at 4 stages between the control and treated samples, and the DEGs were involved in most biological processes. 1270 TFs screened from DEGs were clustered into 158 TF families, such as AP2, RLK-Pelle-DLSVA, and NAC TF families. Genes related to physiological traits were closely related to plant hormone signaling, carotenoid biosynthesis, chlorophyll metabolism, and protein processing. This paper provides a large amount of data for drought research in mung bean.

Thirty Years of Mungbean Genome Research: Where Do We Stand and What Have We Learned?

Mungbean is a socioeconomically important legume crop in Asia that is currently in high demand by consumers and industries both as dried beans and in plant-based protein foods. Marker-assisted and genomics-assisted breeding are promising approaches to efficiently and rapidly develop new cultivars with improved yield, quality, and resistance to biotic and abiotic stresses. Although mungbean was at the forefront of research at the dawn of the plant genomics era 30 years ago, the crop is a "slow runner" in genome research due to limited genomic resources, especially DNA markers. Significant progress in mungbean genome research was achieved only within the last 10 years, notably after the release of the VC1973A draft reference genome constructed using next-generation sequencing technology, which enabled fast and efficient DNA marker development, gene mapping, and identification of candidate genes for complex traits. Resistance to biotic stresses has dominated mungbean genome research to date; however, research is on the rise. In this study, we provide an overview of the past progress and current status of mungbean genomics research. We also discuss and evaluate some research results to provide a better understanding of mungbean genomics.