Transcriptional Profiling of Rice Leaves Undergoing a Hypersensitive Response Like Reaction Induced by Xanthomonas oryzae pv. oryzae Cellulase

A secreted cellulase of Xanthomonas oryzae pv. oryzae induces innate immune responses in rice including a hypersensitive response (HR) like reaction. Microarray analysis was conducted using RNA isolated 12 h following ClsA treatment of leaves. BLAST searches were performed for the 267 (152 up- and 115 downregulated) differentially expressed (>= 2-fold) genes. A number of defense and stress-response functions are upregulated while a number of functions involved in metabolism and transport are downregulated following induction of HR. A significant proportion of the differentially expressed genes (41/267) are predicted to encode transcription factors. Co-infiltration of X. oryzae pv. oryzae suppresses ClsA-induced expression of two transcription factors, OsAP2/ethylene response factor (ERF) and OsRERJ1, that are predicted to be involved in the jasmonic-acid-mediated defense pathway. Transient transfer of OsAP2/ERF via Agrobacterium results in the induction of callose deposition, programmed cell death, and resistance against subsequent X. oryzae pv. oryzae infection.