Molecular cloning and characterization of a Mlo gene in rubber tree (Hevea brasiliensis)

Mlo gene encodes a plant-specific seven-transmembrane domain protein involved in a variety of cellular processes. In this study, a novel Mlo gene from rubber tree (Hevea brasiliensis), designated HbMlo1, was cloned by RT-PCR in rubber tree. The ORF of HbMlo1 was 1551bp in length, encoding a putative protein of 516 amino acids. HbMlo1 was a typical Mlo protein with seven-transmembrane domain. Sequence comparison between HbMlo1 and other Mlo proteins demonstrated that HbMlo1 shared the highest similarity with the Cucumis melo CmMlo1 and Arabidopsis thaliana AtMlo1 with 75.1% and 71.3% sequence identity, respectively. Phylogenetic analysis revealed that HbMlo1, CmMlo1, AtMlo1, AtMlo13, and AtMlo15 formed into the phylogenetic clade II with 100% bootstrap support value. HbMlo1 transcript exhibited tissue specificity, and it was preferentially expressed in leaf. Furthermore, the amount of HbMlo1 transcript was significantly induced by various phytohormones (including ethephon, methyl jasmonate, salicylic acid, abscisic acid, indole-3-acetic acid, and gibberellic acid), H2O2, and wounding treatments. Under drought stress, HbMlo1 exhibited a complex pattern of regulation. However, HbMlo1 expression did not significantly change during powdery mildew infection. These results suggested that HbMlo1 might play a role in phytohormone signaling and abiotic stress response processes in rubber tree.