Abstract
Autophagy plays an important role in maintenance of cellular homeostasis and nutrient translocation under
normal condition and is up-regulated under abiotic and biotic stress for degradation of damaged or
dysfunctional cell constituents in plants. Several lines of evidence indicated that treatments of salt and heat
stress on plants induce ROS production leading to activation of autophagy for removal of potentially highly
toxic denatured proteins in mesophyll cells. In this study, we examined whether autophagy is involved in
protection of photosynthesis activity of soybean leaf under chilling by monitoring a photosynthesis parameter
and ROS production. Photosynthesis System II activity (Fv/Fm) and SPAD values significantly decreased
under chilling and light irradiation whereas those values were affected marginally under chilling and dark.
Significant reactive oxygen species (ROS) production were detected by diaminobenzidine (DAB) and
nitroblue tetrazolium chloride (NBT) staining in soybean leaf under chilling and light irradiation but not under
chilling and dark, indicating that excess ROS production including H2O2 and O2
- damaged photosynthesis
activities in soybean leaf. Reduction of Fv/Fm levels in chilling and light irradiation-treated soybean leaf were
enhanced in the presence of an autophagy inhibitor 3-metyladenine, but alleviated in the presence of an
autophagy activator, acetyl carnitine, compared with that in the absence of those reagents. These results
indicated that autophagy is involved in maintenance of photosynthesis activities in soybean leaf damaged by
ROS produced under chilling and light irradiation.
