Abstract: 【Objective】Previous studies revealed that the expression of pathogenesis-related protein OsPR1A was regulated by the upstream resistance gene Xa21. The rapid induction of OsPR1A protein at early stage after inoculation was crucial in Xa21-mediated rice bacterial blight resistance. The expression of OsPR1A was induced by Xanthomonas oryzae pv. oryzae (Xoo). OsPR1A was well known as a marker gene to demonstrate the reaction between rice and pathogen, however, no direct evidence was obtained for the biological function of OsPR1A. In this paper, transgenic plants overexpression OsPR1A were obtained and the phenotype and agronomic traits were investigated. The relationship between OsPR1A expression and resistance were surveyed to further explore the function of OsPR1A in the process of rice resistance to bacterial blight.【Method】The construct of OsPR1a-OX was transferred to rice recipient 4021 via Agrobacterium-mediated protocol. Positive homozygous transgenic lines were identified by PCR and western blot (WB) respectively. At the mature stage, the phenotype and agronomic traits of OsPR1A overexpression rice plants were investigated, including plant height, spike length, tiller number, seed setting rate and grain size. Rice seedlings of TP309, 4021 and OsPR1A overexpression plants grown for two weeks were inoculated with Xoo at 31℃. The length of lesions was measured at 0, 2, 4, 6, 8, 10, and 12 days post-inoculation (dpi) respectively. At 0, 4 and 6 dpi, the rice leaves of TP309, 4021 and OsPR1A overexpression plants were collected to extract total protein, and the expression profiling of OsPR1A were surveyed by WB.【Result】The OsPR1a-OX transformation vector was constructed and transformed into recipient 4021. Two homozygous OsPR1A overexpression lines (#704 and #709) were identified. At the mature stage, the phenotype and agronomic traits of the OsPR1A overexpression plants were investigated. Compared with the control 4021, #704 and #709 lines showed lower plant height, shorter spike length, fewer tiller number, lower seed-setting rate. The grain size in transgenic rice plants were larger, which might be related to the lower seed-setting rate. At 31℃, the lesion length of OsPR1A overexpression plants was significantly shorter than that of the control 4021 (P<0.05). At 0, 4, and 6 dpi, the abundance of OsPR1A expression of overexpression plants was higher than that of 4021 and TP309, and the high level of OsPR1A protein might contribute to the resistance of Xoo.【Conclusion】OsPR1A overexpression transgenic plants were obtained by the Agrobacterium-mediated method. Overexpression of OsPR1A affected the normal development of rice plants and also enhanced the resistance to bacterial blight mediated by Xa21.

Key words: rice, Xa21, bacterial blight, OsPR1A, vector construction, western blot