Expression and Localization of Arachis Hypogaea 9-Cis Epoxycarotenoid Dioxygenase 1 (AhNCED1) of Peanut Under Water Stress

Expression of AhDREB1, an AP2/ERF Transcription Factor Gene from Peanut, Is Affected by Histone Acetylation and Increases Abscisic Acid Sensitivity and Tolerance to Osmotic Stress in Arabidopsis

Drought stress negatively affects plant growth and development. An increasing number of reports have revealed the involvement of APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription factors (TFs) in biotic and abiotic stress regulation in plants. However, research on these TFs in the peanut plant (Arachis hypogaea) has been limited. Here, we isolated a full-length coding sequence (CDS) of the AP2/ERF family gene AhDREB1 from the peanut plant and showed that its expression was induced by Polyethylene Glycol (PEG) 6000 and exogenous abscisic acid (ABA) treatment. When overexpressed in Arabidopsis, AhDREB1 increased both ABA levels and ABA sensitivity, affected the ABA signaling pathway and increased the expression of downstream drought stress-related genes RD29A, P5CS1, P5CS2 and NCED1. These results demonstrate that AhDREB1 can improve tolerance to drought via the ABA-dependent pathway in Arabidopsis. In the peanut plant, the specific histone deacetylases (HDACs) inhibitor trichostatin A (TSA) promotes AhDREB1 transcription and the enrichment level of H3ac was increased in regions of the AhDREB1 gene during TSA and PEG treatment. In summary, histone acetylation can affect the expression of AhDREB1 under osmotic stress conditions, thereby improving plant drought resistance.

Transcriptomic analysis and discovery of genes in the response of Arachis hypogaea to drought stress

The peanut (Arachis hypogaea) is an important crop species that is threatened by drought stress. The genome sequences of peanut, which was officially released in 2016, may help explain the molecular mechanisms that underlie drought tolerance in this species. We report here a gene expression profiling of A. hypogaea to gain a global view of its drought resistance. Using whole-transcriptome sequencing, we analysed differential gene expression in response to drought stress in the drought-resistant peanut cultivar J11. Pooled samples obtained at 6, 12, 18, 24, and 48 h were compared with control samples at 0 h. In total, 51,554 genes were found, including 49,289 known genes and 2265 unknown genes. We identified 224 differentially expressed transcription factors, 296,335 SNPs and 28,391 InDELs. In addition, we detected significant differences in the gene expression profiles of the treatment and control groups. After comparing the two groups, 4648 genes were identified. An in-depth analysis of the data revealed that a large number of genes were associated with drought stress, including transcription factors and genes involved in photosynthesis-antenna proteins, carbon metabolism and the citrate cycle. The results of this study provide insights into the diverse mechanisms that underlie the successful establishment of drought resistance in the peanut, thereby facilitating the identification of important genes in the peanut related to drought management. Transcriptome analysis based on RNA-Seq is a powerful approach for gene discovery and molecular marker development for this species.

Analysis of phylogenetic and functional diverge in plant nine-cis epoxycarotenoid dioxygenase gene family

During different environmental stress conditions, plant growth is regulated by the hormone abscisic acid (an apocarotenoid). In the biosynthesis of abscisic acid, the oxidative cleavage of cis-epoxycarotenoid catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED) is the crucial step. The NCED genes were isolated in numerous plant species and those genes were phylogenetically investigated to understand the evolution of NCED genes in various plant lineages comprising lycophyte, gymnosperm, dicot and monocot. A total of 93 genes were obtained from 48 plant species to statistically estimate their sequence conservation and functional divergence. Selaginella moellendorffii appeared to be evolutionarily distinct from those of the angiosperms, insisting the substantial influence of natural selection pressure on NCED genes. Further, using exon-intron structure analysis, the gene structures of NCED were found to be conserved across some species. In addition, the substitution rate ratio of non-synonymous (Ka) versus synonymous (Ks) mutations using the Bayesian inference approach, depicted the critical amino acid residues for functional divergence. A significant functional divergence was found between some subgroups through the co-efficient of type-I functional divergence. Our results suggest that the evolution of NCED genes occurred by duplication, diversification and exon intron loss events. The site-specific profile and functional diverge analysis revealed NCED genes might facilitate the tissue-specific functional divergence in NCED sub-families, that could combat different environmental stress conditions aiding plant survival.