Du Yuguang

Cloning and Analysis of BnMPK4, A Novel MAP Kinase Gene Induced by Oligochitosan in Brassica napus

Oligochitosan prepared by enzymatic hydrolysis of chitosan is a potential plant defense elicitor, but how the oligochi-tosan induces the resistance of plants to pathogens is still unclear. So we try to explore the signal transduction pathways of oli-gochitosan inducing defense. We isolated a new cDNA coding for mitogen-activated protein kinase (MAPK), designated BnMPK4 (GenBank: DQ206628), from oilseed (Brassica napus L.) based on our former microarray data. BnMPK4 encodes a 373-amino-acid protein with high sequence similarity to previously reported plant MAPK genes such as AtMPK4 and belongs to the B subgroup of plant MAPK. Bioinformatic analysis showed BnMPK4 contains one phosphorylation motif (TEY) and a con-served CD domain in its C-terminal extension. By using Semi-Quantitative RT-PCR technique we found that BnMPK4 had a con-stitutive expression in seedling leaves and was further up-regulated by treatment with plant hormone jasmonic acid (JA) and fun-gal elicitor oligochitosan but did not respond to salicylic acid (SA) and abscisic acid (ABA). These results suggest a role for BnMPK4 in oligochitosan-induced and JA/ET-regulated defense signalling pathway.

Comparison of Defense Related Enzyme between Oligochitosan Induced Protein Kinase Gene Silenced Transgenic Tobacco and Wild Type Tobacco

Oligochitosan (OC) could regulate plant defense responses in many aspects, but the basis signal transduction pathway is still unclear. In this study, we use transgenic (TG) tobacco as plant material whose OIPK gene was inhibited by antisense transformation, to identify the role oligochitosan induced protein kinase (OIPK) played in OC treated tobacco plants. Pathogen-related (PR) proteins enzymes activity assays and reverse transcriptional polymerase (RT-PCR) were conducted to compare the differences between TG and the corresponding wild type (WT) tobacco plants. Firstly, it was validated that OIPK could induce Phenylalanine ammonialyase (PAL, E.C. 4.3.1.5) and peroxidase (POD, E.C. 1.11.1.7 ) activities in respect to both activation time and activation fold after OC treatment, while OIPK had no influences on polyphenol oxidase (PPO, E.C.I.14.18.1) activity. Secondly, it was found that in TG tobacco, there was nearly just basis pal transcriptional expression after OC treatment, which showed that OIPK could determine pal gene expression in some sense. Thirdly, OIPK could enhance defense related gene transcription chi and glu activation intension and rapidity.