Genome-Wide Survey and Expression Profile Analysis of the Mitogen-Activated Protein Kinase (MAPK) Gene Family in <i>Brassica rapa</i>

Abstract

<div><p>Mitogen-activated protein kinase (MAPK) cascades are fundamental signal transduction modules in plants, controlling cell division, development, hormone signaling, and biotic and abiotic stress responses. Although MAPKs have been investigated in several plant species, a comprehensive analysis of the <i>MAPK</i> gene family has hitherto not been performed in <i>Brassica rapa</i>. In this study, we identified 32 MAPKs in the <i>B</i>. <i>rapa</i> genome by conducting BLASTP and syntenic block analyses, and screening for the essential signature motif (TDY or TEY) of plant MAPK proteins. Of the 32 <i>BraMAPK</i> genes retrieved from the <i>Brassica</i> Database, 13 exhibited exon splicing errors, excessive splicing of the 5' sequence, excessive retention of the 5' sequence, and sequencing errors of the 3' end. Phylogenetic trees of the 32 corrected MAPKs from <i>B</i>. <i>rapa</i> and of MAPKs from other plants generated by the neighbor-joining and maximum likelihood methods suggested that BraMAPKs could be divided into four groups (groups A, B, C, and D). Gene number expansion was observed for <i>BraMAPK</i> genes in groups A and D, which may have been caused by the tandem duplication and genome triplication of the ancestral genome of the <i>Brassica</i> progenitor. Except for five members of the <i>BraMAPK10</i> subfamily, the identified <i>BraMAPKs</i> were expressed in most of the tissues examined, including callus, root, stem, leaf, flower, and silique. Quantitative real-time PCR demonstrated that at least six and five <i>BraMAPKs</i> were induced or repressed by various abiotic stresses and hormone treatments, respectively, suggesting their potential roles in the abiotic stress response and various hormone signal transduction pathways in <i>B</i>. <i>rapa</i>. This study provides valuable insight into the putative physiological and biochemical functions of <i>MAPK</i> genes in <i>B</i>. <i>rapa</i>.</p></div

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