Characterization Of Mitogen-activated Protein Kinase Genes HbMPK3and HbMPK6in Innate Immunity Of Hevea Brasiliensis

Hevea brasiliensis is the main source of natural rubber which plays an irreplaceable role in the national economic development. Rubber tree diseases are one of the most important factors that lead to serious yield losses in rubber production. Mitogen-activated protein kinases (MAPKs) are key components in plant innate immune. Some MAPKs can be activated, which induces expression of plant defence genes against pathogen infection. Functional characterization of MAPKs in disease resistance of rubber tree would improve our knowledge for genetic modification of rubber tree.In this study, sequences of MPK3and MPK6of Hevea brasiliensis were obtained ESTs of MPK3and MPK6from RNA-Seq database. Full-length cDNAs of MPK3and MPK6were obtained by RT-PCR and RACE (Rapid-amplification of cDNA ends), and named HbMPK3and HbMPK6. Sequence analysis showed that both of HbMPK3and HbMPK6encoding366amino acids, both containing a conserved STKc TEY_MAPK_plant domain and11Ser/Thr kinase domains, and a conserved TEY three peptides motif in plant MAPK members.The RT-PCR analysis was carried out to detect the responses of HbMPK3and HbMPK6to plant hormones. The results showed that JA (jasmonate), but not SA (salicylic acid), can induce the expression of HbMPK3and HbMPK6, indicating that HbMPK3and HbMPK6were involved in JA-mediated signaling pathways.The expression of HbMPK3and HbMPK6was induced by a peptide of bacterial flagellin flg22which is a typical PAMP (Pathogen-associated molecular patterns) that can trigger PTI (PAMP-triggered immunity) in plant. In order to investigate the function of HbMPK3and HbMPK6in PTI, two genes were transferred into protoplast cells of Arabidopsis Col-0and mpk.3/6mutants to detect the expression of FRK1. Overexpression of HbMPK3enhanced the PTI in Arabidopsis and recovered marker genes (FRK1) PTI expression level in mpk3mutant. However, overexpression of HbMPK6had no obvious effect on PTI and can not recover the PTI level in mpk6mutant.In addition, we already transformed HbMPK3and HbMPK6into Arabidopsis T-DNA insertion mutants mpk3and mpk6respectively. The TO seeds was obtained. Identification of transgenic lines are ongoing. Further funcational analysis of these transgenic plant will be helpful to demonstrate HbMPK3and HbMPK6in plant resistance responses.