Abiotic stresses such as high salinity, drought and extreme temperatures greatly restrict plant growth and crop production, reducing the average yields of most major crop plants. Under stressful conditions, transcriptome changes are the earliest responses in plants.
In a recent study, the groups of Prof. CHEN Shou-Yi and Prof. ZHANG Jin-Song from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, found the gene GmWRKY27 interacted with the gene GmMYB 174 to improve the stress tolerance in soybean plants.
Soybean is an important crop and provides a large amount of oil and protein resources to the world. Previously, the groups of Prof. CHEN Shou-Yi and Prof. ZHANG Jin-Song have studied soybean genomic features (Tian et al., 2004; Song et al., 2013a) and identified various transcription factors that function in abiotic stress tolerance and oil accumulation (Wang et al., 2007; Liao et al., 2008a; Liao et al., 2008b; Zhou et al., 2008; Wei et al., 2009; Xie et al., 2009; Hao et al., 2011; Song et al., 2013b).
Scientists in their labs recently further characterized the roles of one of these genes, GmWRKY27, in abiotic stress tolerance using transgenic hairy root assay. GmWRKY27 expression was improved by various abiotic stresses. Overexpression and RNAi analysis demonstrate that GmWRKY27 improved salt and drought tolerance in transgenic soybean hairy roots. Measurement of physiological parameters including reactive oxygen species and proline contents also supported this conclusion.
GmWRKY27 inhibits expression of a downstream gene GmNAC29 by binding to the W-boxes in its promoter region. The GmNAC29 is a negative effector of stress tolerance as revealed from the performance of transgenic hairy roots under stress. GmWRKY27 interacts with GmMYB174, which also suppresses GmNAC29 expression and enhances drought stress tolerance. The GmWRKY27 and GmMYB174 may have evolved to adapt to each other for binding to the neighbouring cis-elements in GmNAC29 promoter to co-reduce the promoter activity and gene expression (Figure 1).
Their study discloses a valuable mechanism in soybean for stress response by two associated transcription factors. Manipulation of these genes should facilitate stress tolerance in soybean and other crops.
This work with Dr. WANG Fang and Dr. CHEN Hao-Wei as the co-first authors has been published online on The Plant Journal (DOI: 10.1111/tpj.12879).
This study was supported by the National Key Basic Research Projects, the National Transgenic Research Projects, National Natural Science Foundation of China and State Key Lab of Plant Genomics.
Figure 1. A model of GmWRKY27-mediated abiotic stress response.
GmWRKY27 gene is induced by various abiotic stresses. GmWRKY27 interacts with GmMYB174 and the two TFs cooperatively inhibit the transcription of GmNAC29 by binding to the core sequences in its promoter. The down-regulation of GmNAC29, which may be involved in ROS production by directly up-regulate the expression of GmSPOD1, leads to reduced intracellular ROS level. GmWRKY27 may also increase proline content by indirectly suppressing the transcription of PDH.
