FUNCTIONAL ANALYSIS OF HBMLO12 POWDERY MILDEW INFECTION AND STRESS RESPONSE IN RUBBER TREE HEVEA BRASILIENSIS MUELL ARG.
Powdery mildew locus O (Mlo) gene was first found in barley as a specific powdery mildew resistance gene family. In order to classify the functions of mlo gene in disease resistance and stress response process in rubber tree, a mlo gene, namely Hbmlo12 was cloned from leaves of rubber tree clone CATAS7-33-97. Results showed that the ORF of HbMlo12 was 1721 bp in length, encoding a putative protein of 574 amino acids. HbMlo12 was a typical Mlo protein with eight-transmembrane domain. Sequence comparison between HbMlo12 and other Mlo proteins demonstrated that HbMlo12 shared the highest similarity with the Ricinus communis RcMLO-L12 and Arabidopsis thaliana AtMlo12 with 77% and 64% sequence identity, respectively. Phylogenetic analysis revealed that HbMlo12, RcMlo12-R, RcMlo-L3, AtMlo3, AtMlo12, AtMlo6, and AtMlo2 were grouped into cladeV with 100% bootstrap support value. HbMlo12 expression was tissue specific, and it was preferentially expressed in leaf. HbMlo12 expression significantly changed during powdery mildew infection at the Primary disease. Furthermore, the expression of HbMlo12 was significantly induced by various phytohormones (including ethephon, methyl jasmonate, salicylic acid, abscisic acid, and gibberellic acid). Under drought, wounding stress and indole-3-acetic acid and H2O2 treatment, HbMlo12 expression did not significantly change, but exhibited a complex pattern of regulation. This work provide a theoretical of that HbMlo12 might play a role in phytohormone signaling and abiotic stress response processes in rubber tree.
Keywords: Hevea brasiliensis Muell Arg.; HbMlo12; powdery mildew; stress; phytohormone, rubber, disease resistance, gene, expression, phylogenetic analysis