Differential expression of MEKK subfamily genes in Capsicum annuum L. in response to abscisic acid and drought stress

Abstract

Mitogen-activated protein kinase kinase kinases (MAPKKKs or MEKKs) are crucial components of the MAPK signaling cascades, which play central roles in the signaling transduction pathways for plant growth, development, and response to abiotic stresses such as drought. The MAPKKK gene families in pepper have not been functionally characterized yet. Here, from the pepper genome, we predicted 27 putative MAPKKK genes belonging to the MEKK subfamily (namedCaMEKK1-27), based onin silicoanalysis. Phylogenetic analysis revealed that 14CaMEKKgenes were clustered into A5 of the five groups (A1-A5), of which 9 genes are primarily on chromosomes 2 and 7, and are located close to each other. These nine genes showed transcriptional regulation by treatment with abscisic acid (ABA) and drought stress in quantitative reverse-transcription PCR analysis. Among the ABA- and/or drought-inducedCaMEKKgenes, in a previous study, we isolatedCaAIMK1(Capsicum annuumABA Induced MAP Kinase 1), which plays a positive role in drought resistance via an ABA-dependent pathway. Our expression analysis and functional characterization of the MEKK subfamily genes will provide a better understanding of the functional roles of pepper MAPK cascades in ABA-mediated drought responses.