Open AccessIdentification of Novel Type III Secretion Effectors in Xanthomonas oryzae pv. oryzae
Author(s) -
Ayako Furutani,
Minako Takaoka,
Harumi Sanada,
Yukari Noguchi,
Takashi Oku,
Kazunori Tsuno,
Hirokazu Ochiai,
Seiji Tsuge
Publication year - 2009
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi-22-1-0096
Subject(s) - xanthomonas oryzae , xanthomonas oryzae pv. oryzae , effector , identification (biology) , secretion , biology , xanthomonas , microbiology and biotechnology , botany , bacteria , pathogen , genetics , immunology , biochemistry
Many gram-negative bacteria secrete so-called effector proteins via a type III secretion (T3S) system. Through genome screening for genes encoding potential T3S effectors, 60 candidates were selected from rice pathogen Xanthomonas oryzae pv. oryzae MAFF311018 using these criteria: i) homologs of known T3S effectors in plant-pathogenic bacteria, ii) genes with expression regulated by hrp regulatory protein HrpX, or iii) proteins with N-terminal amino acid patterns associated with T3S substrates of Pseudomonas syringae. Of effector candidates tested with the Bordetella pertussis calmodulin-dependent adenylate cyclase reporter for translocation into plant cells, 16 proteins were translocated in a T3S system-dependent manner. Of these 16 proteins, nine were homologs of known effectors in other plant-pathogenic bacteria and seven were not. Most of the effectors were widely conserved in Xanthomonas spp.; however, some were specific to X. oryzae. Interestingly, all these effectors were expressed in an HrpX-dependent manner, suggesting coregulation of effectors and the T3S system. In X. campestris pv. vesicatoria, HpaB and HpaC (HpaP in X. oryzae pv. oryzae) have a central role in recruiting T3S substrates to the secretion apparatus. Secretion of all but one effector was reduced in both HpaB – and HpaP – mutant strains, indicating that HpaB and HpaP are widely involved in efficient secretion of the effectors.