Over-expression of MAP3K^|^#948;4, an ABA-inducible Raf-like MAP3K that confers salt tolerance in Arabidopsis

Abstract

Mitogen-activated protein kinase (MAPK) cascades play important roles in plant responses to various environmental stimuli, including high salt or drought levels. Arabidopsis MAP3Kδ4 with PAS (period circadian protein, arylhydrocarbon receptor nuclear translocator protein and single-minded protein) domain is one of the Raftype MAPKKKs whose function has not been identified to date. Previous studies have shown that the MAP3Kδ4 overexpressing transformant exhibits vigorous growth. In this study, RT-PCR analysis showed that MAP3Kδ4 transcripts are increased through stress treatments, such as high salt, osmosis, drought and cold and the plant hormone, abscisic acid (ABA). The precipitation of MAP3Kδ4 using its specific antibody showed that ABA treatment markedly induces the activity of this enzyme. Furthermore, the ABA-mediated inhibition of seed germination was relieved in transgenic Arabidopsis over-expressing MAP3Kδ4. These results suggested that MAP3Kδ4 plays an important role in ABA signalling. Transgenic Arabidopsis over-expressing MAP3Kδ4 also exhibited enhanced tolerance to salt stress. The results obtained in this study demonstrated that MAP3Kδ4 was active during ABA-related responses and is involved in both stress tolerance and increased biomass. Therefore, MAP3Kδ4 and its counterpart genes are important with respect to agricultural developments.

A Raf-like protein kinase BHP mediates blue light-dependent stomatal opening

“…1a). However, the physiological functions of the members are largely unknown26. We suspected that some members in the subfamily mediate blue light-dependent stomatal opening.…”

Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE (ANR), a regulator of ABA responses unique to basal land plants and required for desiccation tolerance

“…In addition to the EDR and CTR1 EK kinases, these include two PK kinase paralogs (Raf10 and Raf11) that positively regulate ABA responses in seed development and growth in Arabidopsis (Lee et al, 2015). A third PK kinase (encoded by At4g23050) is ABA activated and confers salt tolerance in Arabidopsis (Shitamichi et al, 2013). The B-group MAP3K family is subdivided into the B1, B2, B3, and B4 subfamilies, of which the B4 subfamily is the most divergent and is not included in our analysis.…”

Arabidopsis thaliana Raf22 protein kinase maintains growth capacity during postgerminative growth arrest under stress

“…A growing body of evidence suggests that Raf‐type MAP3Ks play significant roles in plant growth/development and in stress response signalling. Examples of Raf‐type MAP3Ks with well‐established roles include A. thaliana CONSTITUTIVE TRIPLE RESPONSE1, which functions in the ethylene signal transduction pathway (Kieber, Rothenberg, Roman, Feldmann, & Ecker, ); A. thaliana ENHANCED DISEASE RESISTANCE1, which negatively regulates disease resistance (Frye & Innes, ), stress tolerance, and cell death (Tang, Christiansen, & Innes, ); Oryza sativa (rice) DROUGHT HYPERSENSITIVE MUTANT1, which mediates drought resistance through reactive oxygen species scavenging (Ning, Li, Hicks, & Xiong, ); A. thaliana MAP3Kδ4, which is involved in resistance to salt stress and in ABA signalling (Shitamichi, Matsuoka, Sasayama, Furuya, & Nanmori, ); rice INCREASED LEAF ANGLE1, which regulates mechanical tissue formation in the lamina joint (Ning, Zhang, Wang, Zhou, & Xiong, ); A. thaliana Raf43, which regulates seed germination and seedling growth upon exposure to stresses (Virk et al, ); A. thaliana Raf10 and Raf11, which regulate seed germination and ABA sensitivity (Lee, Lee, Kim, & Kim, ); A. thaliana BLUE LIGHT‐DEPENDENT H+‐ATPASE PHOSPHORYLATION, which mediates stomatal opening in response to blue light (Hayashi, Inoue, Ueno, & Kinoshita, ); and A. thaliana HYDRAULIC CONDUCTIVITY ROOT1, which negatively controls root hydraulic conductivity (Shahzad et al, ). Despite these examples, most Raf kinases remain functionally uncharacterized.…”

“…A growing body of evidence suggests that Raf-type MAP3Ks play significant roles in plant growth/development and in stress response signalling. Examples of Raf-type MAP3Ks with well-established roles include A. thaliana CONSTITUTIVE TRIPLE RESPONSE1, which functions in the ethylene signal transduction pathway (Kieber, Rothenberg, Roman, Feldmann, & Ecker, 1993); A. thaliana ENHANCED DISEASE RESISTANCE1, which negatively regulates disease resistance (Frye & Innes, 1998), stress tolerance, and cell death (Tang, Christiansen, & Innes, 2005); Oryza sativa (rice) DROUGHT HYPERSENSITIVE MUTANT1, which mediates drought resistance through reactive oxygen species scavenging (Ning, Li, Hicks, & Xiong, 2010); A. thaliana MAP3Kδ4, which is involved in resistance to salt stress and in ABA signalling (Shitamichi, Matsuoka, Sasayama, Furuya, & Nanmori, 2013); rice INCREASED LEAF ANGLE1, which regulates mechanical tissue formation in the lamina joint (Ning, Zhang, Wang, Zhou, & Xiong, 2011); A.…”