Journal Article

Identification of functional regions of the HrpZ sub(Psg) protein from Pseudomonas savastanoi pv. glycinea that induce disease resistance and enhance growth in plants

Zhang, Yang, Gao, Xuewen, Gu, Qin, Wu, Huijun, Zhang, Hongyue

2017

Overview

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 HrpZ sub(PsgS1), a 346-amino-acid harpin protein from P. savastanoi pv. glycinea S1. Results showed that proteins HrpZ sub(74-204) and HrpZ sub(1-194) 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 HrpZ sub(PsgS1), such as HrpZ sub(1-102), HrpZ sub(195-238), HrpZ sub(241-248), HrpZ sub(254-298), and HrpZ sub(290-313), was reduced. The activity of the remaining mutants, other than HrpZ sub(200-346), 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 HrpZ sub( Delta 89-124) and HrpZ sub( Delta 254-298) enhanced growth in rice more than wild-type HrpZ sub(PsgS1). 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 HrpZ sub( Delta 89-124) and HrpZ sub( Delta 254-298) induced higher levels of expression in genes related to HR, pathogen defense, and growth. Therefore, the modified proteins HrpZ sub( Delta 89-124) and HrpZ sub( Delta 254-298 may) have potential for development as protein-type biocontrol agents.

• Subject: Pseudomonas / Pseudomonas savastanoi / Virgaviridae / Xanthomonas oryzae