Different Cell Wall-Degradation Ability Leads to Tissue-Specificity between pv and pv.

pv. () and pv. () lead to the devastating rice bacterial diseases and have a very close genetic relationship. There are tissue-specificity differences between and , i.e., only proliferating in xylem vessels and spreading in intercellular space of mesophyll cell. But there is little known about the determinants of tissue-specificity between and . Here we show that can spread in the intercellular spaces of mesophyll cells to form streak lesions. But is restricted to growth in the intercellular spaces of mesophyll cells on the inoculation sites. In vivo, largely breaks the surface and inner structures of cell wall in mesophyll cells in comparison with . In vitro, strongly damages the cellulose filter paper in comparison with . These results suggest that the stronger cell wall-degradation ability of than that of may be directly determining the tissue-specificity.