AUTHOR=Cao Jianbo , Zhang Meng , Xiao Jinghua , Li Xianghua , Yuan Meng , Wang Shiping 

TITLE=Dominant and Recessive Major R Genes Lead to Different Types of Host Cell Death During Resistance to Xanthomonas oryzae in Rice

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01711

DOI=10.3389/fpls.2018.01711

ISSN=1664-462X

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