hrcQ gene determines Xanthomonas oryzae pv. oryzicola to trigger hypersensitive response in nonhost tobacco and pathogenicity in host rice.

hrcQ gene of Xanthomonas oryzae pv.oryzicola(Xoc) is highly conserved in the animal and plant pathogens.It has been postulated that the differentiation at the N-terminal of HrcQ proteins in different plant pathogenic bacteria is related to the secretion of specific effectors through type Ⅲ secretion system(T3SS).However,it is unclear whether HrcQ affects the formation of T3SS and the secretion of T3SS effectors.To understand the effect of HrcQ on the formation of T3SS and the secretion of T3SS effectors,hrcQ mutant of Xoc was generated by knocking-out mutagenesis through allelic exchange.Pathogenicity assays verified that the hrcQ mutant lost the ability to trigger hypersensitive response(HR) in nonhost tobacco and pathogenicity in host rice.The expression of hrcQ was induced when the pathogen interacted with rice cells.The protein-protein interaction assay by yeast two-hybrid system showed that HrcQ could interact with Hpa1,HrcN,HrpB5 and HrpB2.Immunobloting assay confirmed that HrcQ was not secreted through T3SS,whereas the mutation of hrcQ led to no secretion of Hpa1 and HrpB2 through T3SS.These results suggest that HrcQ is the core component of T3SS helping Hpa1 and HrpB2 secret through T3SS to determine HR in tobacco and pathogenicity in rice.All the above also provides a basis for further understanding of the secretion mechanisms by X.oryzae pv.oryzicola T3SS.