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The SlWRKY81 transcription factor inhibits stomatal closure by attenuating nitric oxide accumulation in the guard cells of tomato under drought
Author(s) -
Ahammed Golam Jalal,
Li Xin,
Mao Qi,
Wan Hongjian,
Zhou Guozhi,
Cheng Yuan
Publication year - 2021
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/ppl.13243
Subject(s) - guard cell , wrky protein domain , nitrate reductase , downregulation and upregulation , nitric oxide , stomatal conductance , drought tolerance , microbiology and biotechnology , gene silencing , biology , transcription factor , photosynthesis , chemistry , botany , gene expression , gene , biochemistry , enzyme , transcriptome , endocrinology
The WRKY transcription factors (TFs) play multifaceted roles in plant growth, development, and stress response. Previously, we found that SlWRKY81 negatively regulates tomato tolerance to drought; however, the mechanisms of stomatal regulation in response to drought remain largely unclear. Here, we showed that drought‐induced upregulation in the SlWRKY81 transcripts induced photoinhibition and reduced the net photosynthetic rate in tomato leaves. However, silencing SlWRKY81 alleviated those inhibitions and minimized the drought‐induced damage. A time‐course of water loss showed that SlWRKY81 silencing significantly and consistently reduced leaf water loss, suggesting a role for SlWRKY81 in stomatal movement. Further analysis using light microscopy revealed that SlWRKY81 silencing significantly decreased stomatal aperture and increased the ratio of length to width of stomata under drought. Both biochemical assay and confocal laser scanning microscopy demonstrated that drought‐induced upregulation in SlWRKY81 expression inhibited the nitric oxide (NO) accumulation in the guard cells, which was attributed to the simultaneous declines in the activity of nitrate reductase (NR) and NR expression in tomato leaves. The inspection of 3‐kb sequences upstream of the predicted transcriptional start site of the NR identified three copies of the core W‐box (TTGACC/T) sequence in the promoter region, indicating possible targets of SlWRKY81. Taken together, these data suggest that SlWRKY81 potentially represses NR transcription and thus reduces NO accumulation to attenuate stomatal closure and subsequent drought tolerance. These findings provide an improved understanding of the mechanism of WRKY‐induced regulation of stomatal closure, which can be exploited in the future to enhance drought tolerance in crops.