Early ROS accumulation in chloroplasts of Nicotiana glutinosa infected by Cucumber mosaic virus

Abstract

Reactive oxygen species (ROS) are considered to play an important role on the plant disease resistance. The accumulation of ROS was detected in chloroplasts (not in soluble fractions) from Nicotiana glutinosa leaves inoculated with Cucumber mosaic virus (CMV) in the early stage of infection (3 days post-inoculation (dpi)); though the accumulation of CMV was lower than that at 9 dpi. During the late stage of infection (9 dpi, disease development), ROS accumulation was detected both in cytoplasm and chloroplasts. At 3 dpi, a significant decrease of the activity of chloroplastic ascorbic acid peroxidase (APX) was observed involved in its elimination that correlated with ROS and TBARS accumulation. The decreased activity of chloroplastic APX was considered as a quick response for N. glutinosa to CMV. At the same time, the activity of cytoplasmic APX only slightly decreased. ROS as signaling molecules of infected cells originated from the chloroplast but not the cytoplasm. The damage of membrane by lipid peroxidation increased as ROS generation and the photosynthetic efficiency continues to decline in systemically-infected leaves. It suggested that an alteration of the chloroplastic structure and function was produced in early responses to CMV.