These results suggest that autophagy-like cell death is a feature of the dominant MR gene-mediated resistance to Xoo and vacuolar-mediated cell death is a characteristic of the recessive MR gene-mediated resistance. Application of autophagy inhibitor 3-methyladenine partially compromised Xa1-, Xa4-, and Xa21-mediated resistances, as did Na 2HPO 4 alkaline solution to xa5- and xa13-mediated resistances. In contrast, the xa5- and xa13-mediated resistances to Xoo were associated mainly with vacuolar-mediated cell death characterized by tonoplast disruption of the xylem parenchyma cells. We observed that Xa1-, Xa4-, and Xa21-mediated resistances to Xoo were associated mainly with autophagy-like cell death featured by the formation of autophagosome-like bodies in the xylem parenchyma cells. Three dominant MR genes Xa1, Xa4, and Xa21 and two recessive MR genes xa5 and xa13 that encode very different proteins were used in this study. Here, by ultrastructural examination of xylem parenchyma cells, we show that resistances to Xoo conferred by dominant MR genes and recessive MR genes resulted in different types of programmed cell death (PCD). However, how these MR genes mediated-resistances occur at the cytological level is largely unknown. A number of dominant major disease resistance ( MR) genes and recessive MR genes against Xoo have been cloned and molecularly characterized in the last two decades. oryzae ( Xoo) is the most devastating bacterial disease of rice worldwide.

The bacterial blight caused by Xanthomonas oryzae pv. 2Public Laboratory of Electron Microscopy, Huazhong Agricultural University, Wuhan, China.1National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, China.

Jianbo Cao 1,2, Meng Zhang 1, Jinghua Xiao 1, Xianghua Li 1, Meng Yuan 1 and Shiping Wang 1*

Recessive vs dominant traits