%D 2009 %0 MEDLINE %T Identification of novel type III secretion effectors in Xanthomonas oryzae pv . oryzae . %J Mol Plant Microbe Interact %V 22 %P 96-106 %A Furutani A %A Takaoka M %A Sanada H %A Noguchi Y %A Oku T %A Tsuno K %A Ochiai H %A Tsuge S %M pub19061406 %X 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 .