Cloning and Analysis ofMAPK7Gene Family and Their Promoters from Brassica napus

Mitogen-activated protein kinase (MAPK) is a large family of serine/threonine protein kinase, containing 11 conserved subdomains. MAPK pathways play a central role in transferring information from diverse receptors/sensors to a wide range of cellular responses in plants. Signaling through MAP kinase cascade can lead to cellular responses including cell division, development, hormone, physiology, as well as the response to a broad variety of biotic and abiotic stresses. In this study, the full-length cDNA of MAPK7 gene family was isolated from Brassica napus. There were three members in this gene family, including BnMAPK7-1, BnMAPK7-2, and BnMAPK7-3. Standard mRNA lengths of these genes were 1593, 1434, and 1547 bp. Phylogenetic tree showed that BnMAPK7 gene family was all originated from Brassica rapa, and BnMAPK7-1/-2 were generated from ancestral gene of Bra03723, while BnMAPK7-3 was evolved from ancestral gene of Bra03724. We also cloned promoters of BnMAPK7-1/-2, which contain some light responsive elements, hormone responsive elements and stress response elements. Quantitative real-time PCR (qRT-PCR) showed that BnMAPK7 gene family expressed in all organs tested, and could be induced by phytohormones (MeJA, ABA, and SA), signaling molecules (H2O2), stress (heat) and injury (wounding and Sclerotinia sclerotiorum). This study preliminarily proved that the BnMAPK7 gene family plays certain roles in plant stress responses. In addition, the recombinant BnMAPK7-1/-3 proteins were successfully expressed in Escherichia coli, but the main form of proteins was inclusion body, this result would contribute to further discuss in the future.