Abstract
BackgroundThe NAC (NAM, ATAF and CUC) transcriptional factors constitute a large family with more than 150 members in rice and some of them have been demonstrated to play crucial roles in plant abiotic stress response. Here, we report the characterization of a rice stress-responsive NAC gene, ONAC095, and the exploration of its function in drought and cold stress tolerance.ResultsExpression of ONAC095 was up-regulated by drought stress and abscisic acid (ABA) but down-regulated by cold stress. ONAC095 protein had transactivation activity and the C2 domain in C-terminal was found to be critical for transactivation activity. Transgenic rice lines with overexpression of ONAC095 (ONAC095-OE) and dominant chimeric repressor-mediated suppression of ONAC095 (ONAC095-SRDX) were generated. The ONAC095-OE plants showed comparable phenotype to wild type under drought and cold stress conditions. However, the ONAC095-SRDX plants displayed an improved drought tolerance but exhibited an attenuated cold tolerance. The ONAC095-SRDX plants had decreased water loss rate, increased proline and soluble sugar contents, and up-regulated expression of drought-responsive genes under drought condition, whereas the ONAC095-SRDX plants accumulated excess reactive oxygen species, increased malondialdehyde content and down-regulated expression of cold-responsive genes under cold condition. Furthermore, ONAC095-SRDX plants showed an increased ABA sensitivity, contained an elevated ABA level, and displayed altered expression of ABA biosynthetic and metabolic genes as well as some ABA signaling-related genes.ConclusionFunctional analyses through dominant chimeric repressor-mediated suppression of ONAC095 demonstrate that ONAC095 plays opposite roles in drought and cold stress tolerance, acting as a negative regulator of drought response but as a positive regulator of cold response in rice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0897-y) contains supplementary material, which is available to authorized users.
Highlights
The NAC (NAM, ATAF and CUC) transcriptional factors constitute a large family with more than 150 members in rice and some of them have been demonstrated to play crucial roles in plant abiotic stress response
Bioinformatics analysis indicated that several stress-responsive cis-elements including 1 GCC box, 4 MYC recognition sites, 6 MYB recognition sites and 12 W-boxes are present in the promoter region (1.5 Kb upstream of the start codon) of the ONAC095 gene (Fig. 1b)
Considering that ONAC022 is closely related to ONAC095 [42], we examined whether altered expression of ONAC095 in transgenic plants affected the expression of ONAC022. quantitative real time-PCR (qRT-PCR) data showed that the expression level of ONAC022 in ONAC095-OE and ONAC095-SRDX plants was comparable to that in WT (Fig. 3d), indicating that altered expression of ONAC095 does not affect the expression of ONAC022 in transgenic rice
Summary
The NAC (NAM, ATAF and CUC) transcriptional factors constitute a large family with more than 150 members in rice and some of them have been demonstrated to play crucial roles in plant abiotic stress response. We report the characterization of a rice stress-responsive NAC gene, ONAC095, and the exploration of its function in drought and cold stress tolerance. Environmental constraints such as drought, salt and extreme temperatures often affect adversely plant growth and development, which lead to great loss of productivity worldwide [1]. A total of 5866 genes (2145 up-regulated and 3721 down-regulated), accounting for ~18 % of the annotated genes in rice genome, were differentially expressed during drought stress in rice [11] Such large proportion of differentially expressed genes during a specific abiotic stress response requires a synergistic action of different types of transcription factors (TFs) in both temporal and spatial manners. It was suggested that some of the functionally characterized TF genes may have great potentials in improvement of abiotic stress tolerance in crop plants [18]
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