Identification and characterization of an indole production-upregulated mutant of rice endophytic Pantoea ananatis YJ76

[Objective] To obtain and identify mutants related to indole regulation will provide functional genes responding for bacterial survival adaptability and in-planta colonization/association, which will be significant to the study of indole regulation pathway. [Methods] A mutant library of YJ76 was constructed by mTn5 transposon mutagenesis method, from which the mutant genes could be identified by using the high-efficiency TAIL PCR (hiTAIL-PCR) technique. [Results] A mutant strain named M04 with significantly increased indole production was selected from the mutant library of YJ76, and the mutation site was identified as a new gene (195 bp), which we named as ipc (indole production control) gene. This mutation enhanced the bacterial resistance to heavy metals, tetracycline and acids, and also enhanced the colonizing/plant growth-promoting ability of the endophyte on rice. [Conclusion] By carrying ipc mutation, the mutant strain increased indole production, resulting in the improved survival adaptability and higher association ability on the host rice.