hrcQ Gene Determines Xanthomonas oryzae pv. oryzicola to Trigger Hypersensitive Response in Nonhost Tobacco and Pathogenicity in Host Rice
ZHANG Ding-ding1; ZOU Li-fang2; ZHAO Mei-qin1;ZOU Hua-song2;CHEN Gong-you1,2,*
1 Key Laboratory for Monitoring and Management of Plant Diseases and Insects, Ministry of Agriculture/Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China; 2 School of Agriculture and Biology, Shanghai Jiaotong University, Shanghai 200240, China； *Corresponding author, E-mail: email@example.com
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 Nterminal 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 knockingout 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 proteinprotein interaction assay by yeast twohybrid 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.
Nino-Liu D O, Ronald P C, Bogdanove A J. Xanthomonas oryzae pathovars: Model pathogens of a model crop. Mol Plant Pathol, 2006, 7: 303-324.
Buttner D, Bonas U. Regulation and secretion of Xanthomonas virulence factors. Fems Microbiol Rev, 2010, 34: 107-133.
Zou L F, Wang X P, Xiang Y, et al. Elucidation of the hrp clusters of Xanthomonas oryzae pv. oryzicola that control the hypersensitive response in nonhost tobacco and pathogenicity in susceptible host rice. Appl Environ Microbiol, 2006, 72: 6212-6224.
Alegria M C, Docena C, Khater L, et al. New protein-protein interactions identified for the regulatory and structural components and substrates of the type Ⅲ secretion system of the phytopathogen Xanthomonas axonopodis pathovar citri. J Bacteriol, 2004, 186: 6186-6197.
Rossier O, van den Ackerveken G, Bonas U. HrpB2 and HrpF from Xanthomonas are type Ⅲ-secreted proteins and essential for pathogenicity and recognition by the host plant. Mol Microbiol, 2000, 38: 828-838.
Pozidis C, Chalkiadaki A, Gomez-Serrano A, et al. Type Ⅲ protein translocase-HrcN is a peripheral membrane ATPase that is activated by oligomerization. J Biol Chem, 2003, 278: 25816-25824.
Muller S A, Pozidis C, Stone R, et al. Double hexameric ring assembly of the type Ⅲ protein translocase ATPase HrcN. Mol Microbiol, 2006, 61: 119-125.
Fadouloglou V E, Tampakaki A P, Glykos N M, et al. Structure of HrcQB-C, a conserved component of the bacterial type Ⅲ secretion systems. Proc Natl Acad Sci USA, 2004, 101(1): 70-75.
Morita-Ishihara T, Ogawa M, Sagara H, et al. Shigella Spa33 is an essential C-ring component of type Ⅲ secretion machinery. J Biol Chem, 2006, 281(1): 599-607.
Hopkins C M, White F F, Choi S H, et al. Identification of a family of avirulence genes from Xanthomonas oryzae pv. oryzae. Mol Plant Microbe Interact, 1992, 5: 451-459.
De Feyter R, Kado C I, Gabriel D W. Small, stable shuttle vectors for use in Xanthomonas. Gene, 1990, 88: 65-72.
Oku T, Tanaka K, Iwamoto M, et al. Structural conservation of the hrp gene cluster in Xanthomons oryzae pv. oryzae. J Gen Plant Pathol, 2004, 70: 159-167.
Tsuge S, Furutani A, Fukunaka R, et al. Expression of Xanthomonas oryzae pv. oryzae hrp genes in XOM2, a novel synthetic medium. J Gen Plant Pathol, 2002, 68: 363-371.
Wang L H, He Y W, Gao Y F, et al. A bacterial cell-cell communication signal with cross-kingdom structural analogues. Mol Microbiol, 2004, 51: 903-912.
He Y W, Xu M, Lin K, et al. Genome scale analysis of diffusible signal factor regulon in Xanthomonas campestris pv. campestris: Identification of novel cell-cell communication-dependent genes and functions. Mol Microbiol, 2006, 59: 610-622.
Dow J M, Crossman L, Findlay K, et al. Biofilm dispersal in Xanthomonas campestris is controlled by cell-cell signaling and is required for full virulence to plants. Proc Natl Acad Sci USA, 2003, 100: 10995-11000.
Fouhy Y, Lucey J F, Ryan R P, et al. Cell-cell signaling, cyclic di-GMP turnover and regulation of virulence in Xanthomonas campestris. Res Microbiol, 2006, 157: 899-904.
Dow M, McCarthy Y, O′Donovan K, et al. Cyclic di-GMP as a second messenger linking cell-cell signalling to biofilm formation in the plant pathogen Xanthomonas campestris. FEBS J, 2009, 276: 73-73.
Furutani A, Tsuge S, Oku T, et al. Hpa1 secretion via type Ⅲ secretion system in Xanthomonas oryzae pv. oryzae. J Gen Plant Pathol, 2003, 69: 271-275.