Abstract
The plant-specific NAC transcription factors play important roles in plant response to drought stress. Here, we have compared the expression levels of a subset of GmNAC genes in drought-tolerant DT51 and drought-sensitive MTD720 under both normal and drought stress conditions aimed at identifying correlation between GmNAC expression levels and drought tolerance degree, as well as potential GmNAC candidates for genetic engineering. The expression of 23 selected dehydration-responsive GmNACs was assessed in both stressed and unstressed root tissues of DT51 and MTD720 using real-time quantitative PCR. The results indicated that expression of GmNACs was genotype-dependent. Seven and 13 of 23 tested GmNACs showed higher expression levels in roots of DT51 in comparison with MTD720 under normal and drought stress conditions, respectively, whereas none of them displayed lower transcript levels under any conditions. This finding suggests that the higher drought tolerance of DT51 might be positively correlated with the higher induction of the GmNAC genes during water deficit. The drought-inducible GmNAC011 needs to be mentioned as its transcript accumulation was more than 76-fold higher in drought-stressed DT51 roots relative to MTD720 roots. Additionally, among the GmNAC genes examined, GmNAC085, 092, 095, 101 and 109 were not only drought-inducible but also more highly up-regulated in DT51 roots than in that of MTD720 under both treatment conditions. These data together suggest that GmNAC011, 085, 092, 095, 101 and 109 might be promising candidates for improvement of drought tolerance in soybean by biotechnological approaches.
Highlights
Drought is one of the most devastating abiotic stresses, which negatively impacts plant growth and development [1]
Among 152 GmNACs, which have putative full-length open reading frame, 50 stress-related genes were predicted based on phylogenetic analyses of GmNAC, ANAC and ONAC families [43]. Out of these 50 genes, 38 genes were checked by real-time quantitative PCR (RT-qPCR), and 25 up-regulated and 6 down-regulated genes were identified in roots and/or shoots of 12-day-old soybean seedlings in response to dehydration [43]
To determine whether the differential expression of GmNAC genes would contribute to enhanced drought tolerance we have carried out differential expression analysis of selected genes in a drought-tolerant (DT51) and in a drought-sensitive soybean variety (MTD720)
Summary
Drought is one of the most devastating abiotic stresses, which negatively impacts plant growth and development [1]. In response to water deficit, plants trigger a number of physiological and metabolic processes to promote their survival [2,3]. TFs have been known to play important roles in plant stress responses by regulating various signaling pathways through their binding to the cis-acting element(s) located in promoter region of downstream target genes, thereby activating them, and/or through interaction with other proteins [5]. A significant number of TFs, such as those belonging to AP2/ERF (Apetala 2/ethylene-responsive element binding factor), bZIP (basic-domain leucine zipper), MYB (myeloblastosis), WRKY, and NAC (NAM—no apical meristem, ATAF—Arabidopsis transcription activation factor, and CUC—cup-shaped cotyledon) families, have been reported to be involved in regulation of drought stress responses [6,7,8,9,10].
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