Reactive oxygen species in the regulation of photosynthetic genes by ultraviolet-B radiation (UV-B: 280–320 nm) in green and etiolated buds of pea ( Pisum sativum L.)

Abstract

Reactive oxygen species (ROS) have been shown to be components of the signal transduction pathway(s) leading to the down-regulation of photosynthetic genes in response to UV-B radiation in green organs. Young, etiolated tissue has been found to be more tolerant of damaging UV-B radiation. In this paper the effects of supplementary UV-B radiation on the expression of photosynthetic genes, generation of ROS and activity of antioxidant enzyme systems have been studied in etiolated pea buds and compared with previously published results from green buds. Transcripts for Lhcb, RbcS and rbcL are down-regulated in green buds but transiently up-regulated in etiolated buds. ROS levels increase in response to UV-B radiation in green buds but transiently in etiolated buds. However, ROS levels are generally higher in etiolated than green buds. After 54 h treatment, differences between the initially etiolated and green buds are no longer detectable. UV-B causes similar increases in the activities of ascorbate peroxidase, superoxide dismutase and glutathione reductase in both green and etiolated buds, without measurably affecting transcript levels. The results indicate that UV-B signal pathway(s) involve ROS in both green and etiolated tissue, but differences do exist with respect to the relationships between antioxidant capacity, ROS levels and changes in the level of photosynthetic transcripts.