Abstract
The NAC proteins form one of the largest families of plant-specific transcription factors (TFs) and play essential roles in developmental processes and stress responses. In this study, we characterized a NAC domain transcription factor, OoNAC72, from a legume Oxytropis ochrocephala. OoNAC72 was proved to be localized in the nuclei in tobacco lower epidermal cells and had transcriptional activation activity in yeast, confirming its transcription activity. OoNAC72 expression could be induced by drought, salinity and exogenous abscisic acid (ABA) in O. ochrocephala seedlings. Furthermore, over-expression of OoNAC72 driven by CaMV35S promoter in Arabidopsis resulted in ABA hypersensitivity and enhanced tolerance to drought and salt stresses during seed germination and post-germinative growth periods. In addition, over-expression of OoNAC72 enhanced the expression of stress-responsive genes such as RD29A, RD29B, RD26, LEA14, ANACOR19, ZAT10, PP2CA, and NCED3. These results highlight the important regulatory role of OoNAC72 in multiple abiotic stress tolerance, and may provide an underlying reason for the spread of O. ochrocephala.
Highlights
Oxytropis ochrocephala Bunge, one of the toxic Oxytropis locoweeds, distributed widely among Northwest China, where the plant often suffered from stress environment such as drought, high soil salinity and low temperature
Further phylogenetic analysis confirmed that the relatedness of the predicted protein to AtNAC72 was highly homologous with those of Medicago truncatula and Cicer arietinum (Supplementary Figure S2). This O. ochrocephala gene was designated as OoNAC72 (MH142381)
The stomatal apertures index of wild type (WT) plants decreased from 0.47 to 0.25, while the OX1 and OX2 lines dropped from 0.48 and 0.52 to 0.12 and 0.15 (Figure 9F). It indicated that the OoNAC72-OX lines were more rapid and variable in stomatal conductance. These results indicated that overexpression of OoNAC72 gene led to increased abscisic acid (ABA) sensitivity, which resulted in retarded growth of transgenic plants
Summary
Oxytropis ochrocephala Bunge, one of the toxic Oxytropis locoweeds, distributed widely among Northwest China, where the plant often suffered from stress environment such as drought, high soil salinity and low temperature. O. ochrocephala can rapidly replace local forages grass species because of its unpalatability and strong biotic stress tolerance. Grasslands infested by O. ochrocephala lead to tremendous losses to livestock husbandry, as well as great damage to the grassland ecological equilibrium (Zhao et al, 2013; He et al, 2015). Existing research on O. ochrocephala mainly focused on surveys, allelopathy and toxicological studies of distribution (Tulsiani et al, 1988; Zhao et al, 2013), and have not yet investigated its resistance mechanism. Plants must respond to those stresses by regulating the resistance-related genes. Transcription factors play an extremely important role in the process of stresses response
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