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The sweet sorghum SbWRKY50 is negatively involved in salt response by regulating ion homeostasis

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The WRKY transcription factor family is involved in responding to biotic and abiotic stresses. Its members contain a typical WRKY domain and can regulate plant physiological responses by binding to W-boxes in the promoter regions of downstream target genes. We identified the sweet sorghum SbWRKY50 (Sb09g005700) gene, which encodes a typical class II of the WRKY family protein that localizes to the nucleus and has transcriptional activation activity. The expression of SbWRKY50 in sweet sorghum was reduced by salt stress, and its ectopic expression reduced the salt tolerance of Arabidopsis thaliana plants. Compared with the wild type, the germination rate, root length, biomass and potassium ion content of SbWRKY50 over-expression plants decreased significantly under salt-stress conditions, while the hydrogen peroxide, superoxide anion and sodium ion contents increased. Real-time PCR results showed that the expression levels of AtSOS1, AtHKT1 and genes related to osmotic and oxidative stresses in over-expression strains decreased under salt-stress conditions. Luciferase complementation imaging and yeast one-hybrid assays confirmed that SbWRKY50 could directly bind to the upstream promoter of the SOS1 gene in A. thaliana. However, in sweet sorghum, SbWRKY50 could directly bind to the upstream promoters of SOS1 and HKT1. These results suggest that the new WRKY transcription factor SbWRKY50 participates in plant salt response by controlling ion homeostasis. However, the regulatory mechanisms are different in sweet sorghum and Arabidopsis, which may explain their different salt tolerance levels. The data provide information that can be applied to genetically modifying salt tolerance in different crop varieties.

Key message

(1) Sweet sorghum SbWRKY50 is negatively involved in salt response.

(2) Over-expression of SbWRKY50 in A. thaliana affects plant growth, ROS and the ion contents.

(3) SbWRKY50 could directly bind to the upstream promoter of the SOS1 gene in A. thaliana and the promoter of SOS1 and HKT1 in sweet sorghum.

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We are grateful for financial support from the National Natural Science Research Foundation of China (31871538), the National Key R&D Program of China (2018YFD1000700, 2018YFD1000704), the Major Program of Shandong Provincial Natural Science Foundation (2017C03), the Opening Foundation of Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology (SDKL2018008-3). We thank Lesley Benyon, PhD, from Liwen Bianji, Edanz Group China (www.liwenbianji.cn/ac), for editing the English text of a draft of this manuscript.

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Yushuang Song, Jinlu Li and Yi Sui imitated the manuscript. Yushuang Song and Jinlu Li performed experiments; Yushuang Song, Guoliang Han, Yi Zhang and Shangjing Guo collected data and carried out all analyses; Na Sui and Yi Sui conceptualized the idea and revised the manuscript. All authors read and approved the final manuscript.

Correspondence to Na Sui.

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Song, Y., Li, J., Sui, Y. et al. The sweet sorghum SbWRKY50 is negatively involved in salt response by regulating ion homeostasis. Plant Mol Biol (2020). https://doi.org/10.1007/s11103-020-00966-4

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  • Sweet sorghum
  • SbWRKY50
  • Salt stress
  • SOS1
  • Ion homeostasis