Early responses to dehydration in contrasting wild Arachis species

Abstract

Wild peanut relatives (Arachis spp.) are genetically diverse and were selected throughout evolution to a range of environments constituting, therefore, an important source of allelic diversity for abiotic stress tolerance. In particular, A. duranensis and A. stenosperma, the parents of the reference Arachis A-genome genetic map, show contrasting transpiration behavior under limited water conditions. This study aimed to build a comprehensive gene expression profile of these two wild species under dehydration stress caused by the withdrawal of hydroponic nutrient solution. For this purpose, roots of both genotypes were collected at seven time-points during the early stages of dehydration and used to construct cDNA paired-end libraries. Physiological analyses indicated initial differences in gas exchange parameters between the drought-tolerant genotype of A. duranensis and the drought-sensitive genotype of A. stenosperma. High-quality Illumina reads were mapped against the A. duranensis reference genome and resulted in the identification of 1,235 and 799 Differentially Expressed Genes (DEGs) that responded to the stress treatment in roots of A. duranensis and A. stenosperma, respectively. Further analysis, including functional annotation and identification of biological pathways represented by these DEGs confirmed the distinct gene expression behavior of the two contrasting Arachis species genotypes under dehydration stress. Some species-exclusive and common DEGs were then selected for qRT-PCR analysis, which corroborated the in silico expression profiling. These included genes coding for regulators and effectors involved in drought tolerance responses, such as activation of osmosensing molecular cascades, control of hormone and osmolyte content, and protection of macromolecules. This dataset of transcripts induced during the dehydration process in two wild Arachis genotypes constitute new tools for the understanding of the distinct gene regulation processes in these closely related species but with contrasting drought responsiveness. In addition, our findings provide insights into the nature of drought tolerance in wild germoplasm, which might be explored as novel sources of diversity and useful wild alleles to develop climate-resilient crop varieties.

Characterization of raffinose metabolism genes uncovers a wild Arachis galactinol synthase conferring tolerance to abiotic stresses

“…Besides being the ortholog of AtGolS2 in A. duranensis, the AdGolS3 gene was selected for further functional analysis since it exhibited differential expression behavior between the drought-tolerant A. duranensis and the drought-sensitive A. stenosperma, in both severe and moderate water-limited conditions. Moreover, our previous qRT-PCR expression analysis 21 showed that AdGolS3 had a higher magnitude of expression in the tolerant A. duranensis throughout the dehydration treatment. Together, these findings indicate AdGolS3 as a putative regulator gene of the RFO pathway in the A. duranensis drought tolerance mechanisms that could be involved in the early and differential responses to severe and moderate processes of water loss.…”

“…The expression patterns of the 28 A. duranensis RFO metabolism genes in response to two types of drought imposition (dehydration and dry-down) were analyzed using our previous transcriptome data obtained from the drought-tolerant accession K7988 of A. duranensis and the drought-sensitive accession V10309 of A. stenosperma 21 . This analysis revealed that the expression of most of the genes involved in RFO metabolism were modulated in response to water deficit, with distinct patterns and expression levels depending on the type of stress imposed and, to a lesser extent, on the Arachis genotype (Fig.…”

“…Wild and cultivated Arachis genotypes exhibit contrasting transpiration behaviors under water-limited conditions, with variable levels of water stress tolerance among the wild species 43 . Accordingly, the accessions K7988 of A. duranensis and V10309 of A. stenosperma have been selected as the drought-tolerant and the drought-sensitive genotypes, respectively, in our functional genomics studies 18 , 20 , 21 , 23 , 24 . Here, the comprehensive expression analysis conducted in these genotypes revealed that most of the 28 A. duranensis genes involved in RFO metabolism, and their orthologs in A. stenosperma , are responsive to drought imposition.…”

“…Illumina RNA-seq data previously obtained by our group were used to determine the in silico expression profiles of GolS, RS, STS, AGAL and BFLUCT genes in Arachis spp. This data comprises: (1) Transcripts expressed in roots of A. duranensis and A. stenosperma plants submitted to dehydration treatment, by the withdrawal of hydroponic nutrient solution from 25 to 150 min 21 and pooled in equal amounts, a treatment which we previously showed to induce major alterations in the transcriptome of these species. (2) Transcripts expressed in A. duranensis and A. stenosperma plants subjected to a decreased in soil availability with withholding of irrigation for four days, a treatment which induced proteomic and transcriptomic alterations 24 .…”

Comparative Transcriptome Analysis Reveals Molecular Defensive Mechanism of Arachis hypogaea in Response to Salt Stress

“…Transcriptomic approach is an effective tool which provides a global information towards the gene expression patterns of a plant organism under any conditions, such as drought, light, temperature, aflatoxin, and salinity stress. Numerous studies about transcriptomic characteristics of peanut have been conducted to evaluate the expression pattern of induc-ible genes under abiotic and biotic stress conditions [25,[34][35][36][37][38][39]. Transcriptome data are valuable resources for exploring plants under stress conditions.…”