Study On The Mechanism Of RCA Protein In Resistanceof Oryza Meyeriana To Xanthomonas Oryza Pv.oryzae

Xanthomonas oryza pv.oryzae?Xoo?causes rice bacterial blight?BB?,one of the most destructive bacterial diseases of rice worldwide.Oryza meyeriana is one of the most important wild rice resources all over China and has long been known to possess high BB resistance and so research on BB resistance mechanism of O.meyeriana has great significance for the utilization of this wild rice in rice resistance breedingprograms.1.Resistance identification showed that O.meyeriana was highly resistant to rice BB and the bacteria of Xoo mainly existed in the leaf xylem vessels.A large number of bacteria were found in xylem vessels both in the wild and the cultivated rice,indicating that Xoo can infect the leaves of O.meyeriana and then the BB resistance of this wild rice is not due to its non-host nature but to its own resistance mechanism.2.In the early stage of Xoo inoculation,the decrease in photosynthetic electron transport rate of O.meyeriana was due to the decline in photosynthetic carbon assimilation efficiency that was caused by the reduction in the activation state of its Ribulose-1,5-bisphosphate carboxylase/oxygenase?Rubisco?.The reduction in Rubisco activation state was not resulted from the decrease in the total content of Rubisco activase?RCA?but the transfer of RCA from the chloroplast stroma to the thylakoid membrane after Xoo inoculation.3.Further study showed that the large accumulation of H₂O₂ in the chloroplasts induced RCA transfer from chloroplast stroma to thylakoid membrane in O.meyeriana.This association of RCA to thylakoid membrane involved many factors and might be specific in O.meyeriana.It is speculated that this specific association contributed to the protection of thylakoid membrane and its binding protein fromH₂O₂damage caused by Xoo infection.Based on the mentioned results,we suggested that RCA was involved in the BB resistance of O.meyeriana,which revealed that RCA may have other new functions in addition to its role in activating Rubisco.