Divergent evolutionary patterns of the MAPK cascade genes in Brassica rapa and plant phylogenetics

Peng Wu,Ying Li,Xilin Hou,Wenli Wang

doi:10.1038/hortres.2017.79

Abstract

Mitogen-activated protein kinase (MAPK) cascade signal transduction modules play crucial roles in regulating many biological processes in plants. These cascades are composed of three classes of hierarchically organized protein kinases, MAPKKKs, MAPKKs and MAPKs. Here, we analyzed gene retention, phylogenetic, evolution and expression patterns of MAPK cascade genes in Brassica rapa. We further found that the MAPK branches, classes III and IV, appeared after the split of bryophytes and green algae after analyzing the MAPK cascade genes in 8 species, and their rapid expansion led to the great size of the families of MAPKs. In contrast, the ancestral class I subfamily of MAPKK gene families have been highly conserved from algae to angiosperms. For the MAPKKK family, the MEKK and Raf subfamily share a common evolutionary origin, and Raf plays a major role in the expansion of the MAPKKK gene family. The cis-elements and interaction network analyses showed the important function of MAPK cascade genes in development and stress responses in B. rapa. This study provides a solid foundation for molecular evolution analyses of MAPK cascade genes.

Highlights

Based on their exposure to environmental stress, plants have constructed complex signaling networks to adapt to different stress conditions.[1]
Comparison of nucleotide distances showed that BrMAPKs and BrMAPKKKs diverged approximately 8.5 MYA, earlier than BrMAPKKs that separated at 12.5 MYA
After comparing the MAPK kinases (MAPKKs) genes in V. vinifera and B. rapa, we found that B. rapa had a relatively large number of MAPKK genes compared to V. vinifera

Summary

Introduction

Based on their exposure to environmental stress, plants have constructed complex signaling networks to adapt to different stress conditions.[1]. MAPKKs, in turn, are activated by MAPKKKs when serine and threonine residues in the S/TXXXXXS/T motif are phosphorylated.[3,4,5,6,7,8,9]. MAPK pathways are relatively wellcharacterized cascades.[10] In plants, genome-wide analyses of MAPK cascades (MAPKKK—MAPKK-MAPK) have been reported in several species.[11,12,13,14,15,16,17,18] In Arabidopsis, 23 MAPKs, 10 MAPKKs, and 80 putative MAPKKKs have been identified. MAPK and MAPKK genes in plants are each divided into four distinct classes (classes A, B, C, and D), whereas MAPKKK genes are classified into the following three subfamilies: (1) MEKK, (2) Raf and (3) ZIK

Methods

Findings

Discussion

Conclusion