Expression of wild soybean WRKY20 in Arabidopsis enhances drought tolerance and regulates ABA signalling

Abstract

The WRKY-type transcription factors are involved in plant development and stress responses, but how the regulation of stress tolerance is related to plant development is largely unknown. GsWRKY20 was initially identified as a stress response gene using large-scale Glycine soja microarrays. Quantitative reverse transcription-PCR (qRT-PCR) showed that the expression of this gene was induced by abscisic acid (ABA), salt, cold, and drought. Overexpression of GsWRKY20 in Arabidopsis resulted in a decreased sensitivity to ABA during seed germination and early seedling growth. However, compared with the wild type, GsWRKY20 overexpression lines were more sensitive to ABA in stomatal closure, and exhibited a greater tolerance to drought stress, a decreased water loss rate, and a decreased stomatal density. Moreover, microarray and qRT-PCR assays showed that GsWRKY20 mediated ABA signalling by promoting the expression of negative regulators of ABA signalling, such as AtWRKY40, ABI1, and ABI2, while repressing the expression of the positive regulators of ABA, for example ABI5, ABI4, and ABF4. Interestingly, GsWRKY20 also positively regulates the expression of a group of wax biosynthetic genes. Further, evidence is provided to support that GsWRKY20 overexpression lines have more epicuticular wax crystals and a much thicker cuticle, which contribute to less chlorophyll leaching compared with the wild type. Taken together, the findings reveal an important role for GsWRKY20 in enhancing drought tolerance and regulating ABA signalling.

The rice transcription factor OsWRKY47 is a positive regulator of the response to water deficit stress

“…On the other hand, the expression of the barley HvWRKY38 in Paspalum notatum Flugge increased the drought tolerance of the transgenic plants (Xiong et al 2010). Similar results were obtained when the Glycine Soja GsWRKY20 was expressed in Arabidopsis (Luo et al 2013) and the maize ZmWRKY58 was overexpressed in transgenic rice (Cai et al 2014). In rice, the overexpression of OsWRKY7 (Ramamoorthy et al 2008), OsWRKY05, OsWRKY43, OsWRKY1, OsWRKT2 (Berri et al 2009) and OsWRKY11 ) was shown to improved drought tolerance.…”

Genome-wide analysis of WRKY gene family in the sesame genome and identification of the WRKY genes involved in responses to abiotic stresses

“…The functions of the 10 AtWRKY gene orthologs have been determined and all are involved in responses to abiotic stresses in Arabidopsis. AtWRKY13 and AtWRKY20 regulate tolerance to drought stress [54,55] and their sesame orthologs, SiWRKY6 and SiWRKY40, are also highly expressed in response to drought. Therefore, we conclude that the SiWRKY orthologs of AtWRKY genes also play key roles in the tolerance of abiotic stresses in sesame.…”

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

“…In many cases, comparative genomics leads to new findings in agriculturally and economically important crops (Marchive et al 2007;Mare et al 2004;Petitot et al 2013;Shekhawat et al 2011). Recently, Luo et al (2013) have described that in wild soybean, Glycine soja, GswRKY20 promotes the expression of negative regulators of ABA signaling while repressing positive regulators. when overexpressed, GsWRKY20-overexpressing plants show higher tolerance to drought with a significant decline in water loss and stomatal density (Luo et al 2013).…”

“…Recently, Luo et al (2013) have described that in wild soybean, Glycine soja, GswRKY20 promotes the expression of negative regulators of ABA signaling while repressing positive regulators. when overexpressed, GsWRKY20-overexpressing plants show higher tolerance to drought with a significant decline in water loss and stomatal density (Luo et al 2013). This study shows that GswRKY20 plays an important role in ABA-mediated stomatal closure, which ultimately leads to increased resistance to drought.…”