Functional analysis of rubber tree receptor-like cytoplasmic kinase HbBIK1 in plant root development and immune response

Nature rubber from rubber tree is one of the most important raw materials for industry. However, rubber trees have been seriously affected by fungal diseases, resulting in large yield loss of nature rubber. Therefore, it is important to identify the disease resistance-related genes for genetically engineered breeding of disease resistance in rubber tree. In this study, the homologous gene of Arabidopsis thaliana receptor-like kinase AtBIK1, HbBIK1, was selected from rubber tree. The full length of HbBIK1 gene was 1260 bp of 419 aa with an intracellular kinase motif. HbBIK1 expression was induced by Oidium heveae Steinmann infection, indicating that HbBIK1 might be involved in response to O. heveae Steinmann infection. The expression level of HbBIK1 was also induced by jasmonic acid (JA) treatment, but not by salicylic acid (SA) and ethylene (ET) treatments. In addition, HbBIK1 was specifically localized on plasma membrane of rubber tree mesophyll protoplasts. Transgenic HbBIK1 lines using AtBIK1 native promoter could rescue not only root length but also disease sensitivity to Alternaria brassicicola in A. thaliana bik1 mutant, indicating the functional similarity between AtBIK1 and HbBIK1. These results showed that HbBIK1 might involve in plant disease resistance and could be used as a candidate disease-related gene for defense genetic breeding in rubber tree.