Co-expression of AtbHLH17 and AtWRKY28 confers resistance to abiotic stress in Arabidopsis

Abstract

Stress adaptation in plants involves altered expression of many genes through complex signaling pathways. To achieve the optimum expression of downstream functional genes, we expressed AtbHLH17 (AtAIB) and AtWRKY28 TFs which are known to be upregulated under drought and oxidative stress, respectively in Arabidopsis. Multigene expression cassette with these two TFs and reporter gene GUS was developed using modified gateway cloning strategy. The GUS assay and expression analysis of transgenes in transgenic plants confirmed the integration of multigene cassette. The transgenic lines exhibited enhanced tolerance to NaCl, Mannitol and oxidative stress. Under mannitol stress condition significantly higher root growth was observed in transgenics. Growth under stress and recovery growth was substantially superior in transgenics exposed to gradual long term desiccation stress conditions. We demonstrate the expression of several downstream target genes under various stress conditions. A few genes having either WRKY or bHLH cis elements in their promoter regions showed higher transcript levels than wild type. However, the genes which did not have either of the motifs did not differ in their expression levels in stress conditions compared to wild type plants. Hence co-expressing two or more TFs may result in upregulation of many downstream target genes and substantially improve the stress tolerance of the plants.

A systems biology perspective on the role of WRKY transcription factors in drought responses in plants

“…Up-regulation of multiple TFs by water stress may lead to enhanced expression of target genes. Babitha et al (2013) showed that co-expression of AtWRKY28 and AtbHLH17 resulted in increased expression of different target genes in response to various abiotic stresses like drought, salt and oxidative stress in Arabidopsis (Babitha et al 2013). various downstream target genes like RD29A, rd22 and FSD2 were found to have w boxes in their promoter regions whereas KIN1 and ADH1 have G-box elements while P5C5 and LEA14 have both elements.…”

“…However, there is not a simple relationship between the presence or absence of binding sites and expression levels, genes having binding site for both classes of transcription factors do not show higher expression when compared with the ones which have just one of the two binding sites alone. However, it is clear that co-expression of multiple transcription factors leads to up-regulation of more targets (Babitha et al 2013). Hence, cooperative behavior of the different transcription factors appears to result in tighter regulation of the molecular responses to different stress conditions.…”

Emerging tools, concepts and ideas to track the modulator genes underlying plant drought adaptive traits: An overview

“…2,7,11,[65][66][67] It has also been reported recently that ectopic expression of stress specific transcription factors in combination aids in combating multiple abiotic stresses. [68][69][70] Large numbers of review articles have compiled the relevance of multiple upstream regulatory as well as downstream functional genes underlying a wide array of drought tolerance traits in imparting abiotic stress tolerance ( Table 2). There is a well defined and tightly regulated signaling network starting from stress signal perception up to downstream functional gene activation, and the genes which regulate their activity, whichever be the tolerance mechanism.…”

GmWRKY53, a water- and salt-inducible soybean gene for rapid dissection of regulatory elements in BY-2 cell culture

“…Recently, Babitha et al (2012) have shown that co-expression of AtbHLH17 and AtWRKY28 confers resistance to abiotic stress in Arabidopsis. 23 The transgenic lines show enhanced tolerance to multiple abiotic stresses like drought, salt and oxidative stress via regulation of more number of targets.…”

“…Recently, Babitha et al (2012) have shown that co-expression of AtbHLH17 and AtWRKY28 confers resistance to abiotic stress in Arabidopsis. 23 The transgenic lines show enhanced tolerance to multiple abiotic stresses like drought, salt and oxidative stress via regulation of more number of targets. Thus, we hypothesize utilizing the current knowledge reported in this study for GmWRKY53, which is a salt and water-stress inducible gene has full potential for being used as suitable candidate that will provide novel insights toward functionality in response to abiotic stress.…”