文摘
Harpin HrpZ from the plant-pathogen Pseudomonas spp. elicits the hypersensitive response (HR), pathogen defense responses, and enhances growth in plants. To identify regions of HrpZ related to these bioactivities, we constructed 11 mutants of HrpZPsgS1, a 346-amino-acid harpin protein from P. savastanoi pv. glycinea S1. Results showed that proteins HrpZ74–204 and HrpZ1–194 could not induce macroscopic HR but could elicit microscopic HR in tobacco. The HR elicitation activity of mutant proteins with other C-terminal deletions in HrpZPsgS1, such as HrpZ1–102, HrpZ△195–238, HrpZ△241–248, HrpZ△254–298, and HrpZ△290–313, was reduced. The activity of the remaining mutants, other than HrpZ200–346, which lacks part of the N-terminus, was similar to wild-type. These results indicate that the C-terminus is indispensable for HR elicitation, and that parts of the N-terminus play a regulatory role. Also, mutants HrpZΔ89–124 and HrpZΔ254–298 enhanced growth in rice more than wild-type HrpZPsgS1. These mutants were also more effective at inducing resistance to Xanthomonas oryzae pv. oryzae in rice and to Tobacco Mosaic Virus (TMV) in tobacco. qRT-PCR assays showed that HrpZΔ89–124 and HrpZΔ254–298 induced higher levels of expression in genes related to HR, pathogen defense, and growth. Therefore, the modified proteins HrpZΔ89–124 and HrpZΔ254–298 may have potential for development as protein-type biocontrol agents.