An atypical chemotactic receptor gene of Xanthomonas oryzae pv.oryzae is associ-ated with bacterial swimming and early infection
After annotating the genome of Xanthomonas oryzae pv.oryzae strain PXO99A-GX,we found an a-typical chemoreceptor gene PXO_01024,which encodes a protein with two transmembrane domains(TMD)and a methyl-accepting domain(MA)but without the ligand-binding domain(LBD).To understand the biological function of PXO_01024,we constructed the PXO_01024 deletion mutant DM01024 and its complemented strain CDM01024 by homologous double exchange method.Deletion of PXO_01024 resulted in the reduced formation of biofilm and almost loss of bacterial swimming,while in CDM01024 the swimming motility and biofilm forma-tion ability were restored to wild-type levels.The virulence of DM01024 was not significantly different from that of the wild-type strain when inoculation of wounded host plants was performed.However,when unwounded plants were inoculated with the spraying inoculation method,the disease index caused by DM01024 was signifi-cantly reduced compared with that caused by the wild-type strain and complemented strain CDM01024,indica-ting that PXO_01024 played a role in early infection of Xoo.The chemotaxis of these strains was subsequently detected by capillary method,and the results showed that DM01024 showed significantly reduced chemotaxis to methionine,alanine,leucine,glycine,asparagine,phenylalanine,isoleucine,glucose,maltose,xylose,fructose,succinic acid,and tartaric acid compared with the wild-type strain.This study demonstrated that the atypical chemo-tactic receptor gene PXO 01024 is associated with chemotaxis,swimming motility,and early infection of Xoo.
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