Abstract
Hypersensitive response (HR) cell death that is one of the plant immune responses is induced by the effector protein secreted into plant cells through the Hrp secretion system (Type III secretion system, T3SS). Acidovorax avenae N1141 avirulent strain induces plant immune responses in rice. To clarify the induction mechanism of HR cell death in Oryza sativa (rice), we analyzed genome sequence of N1141 strain and found 30 kbp hrp gene cluster encoding T3SS. Since the deletion mutant of T3SS in N1141 strain (N1141Δhrc) did not induce HR cell death, effectors secreted through T3SS would cause HR cell death in rice. Therefore we next attempted to identify the effectors using proteomics. Several proteins were specifically accumulated in N1141Δhrc strain when accumulated proteins in N1141 and N1141Δhrc strains were compared. Among the identified protein, disruption mutation in Ahp1 gene resulted in no HR cell death in cultured rice cells. Further transformation of Ahp1 in rice cells caused induction of HR cell death, suggesting that Ahp1 is a candidate of effector involved in induction of HR cell death.
