Chlorophyll changes and photosynthetic genes expression in UV-B radiation treatments in Brassica napus

The depletion of stratospheric ozone layer causes increase in ultra violet radiation incidence on earth. Basically, plant species show different response to UV radiation. This research was carried out because of the importance of photosynthetic gene expression and simultaneous study of relative chlorophyll loss rate under UV-B radiation condition. Seed of Brassica napus cv. Bristol was planted in light filler and vernalized at 4 c, then transferred into the research greenhouse. The study was carried out in a completely randomize design with 4 UV-B treatments and 4 replicates. Leaf samples were taken at the maximum vegetative growth stage (beginning of flowering). RNA was extracted and blotted onto nylon membrane. Northern hybridization was then done by using radioactive probes of photosynthetic gene clones RBCS, Lhc2, cab and antioxidant gene (Thio) and gene expression pattern was investigated. Also, chlorophyll a and b content and cellular oxidative index (TBARM) were measured under UV-B radiation. Chlorophyll a content showed linear decrease with increase in UV-B intensity. Whereas, chlorophyll b was more stable especially at more intensified UV-B (every two-day) treatment. This was relevant to consistency of Lhc2 expression under UV-B radiation. The decrease of RBCS gene expression was more than that of Lhc2 and cab. It shows the higher sensitivity of this gene to increased reactive oxygen species. The amount of TBARM and gene expression of Thio showed considerable increase with increase in UV-B radiation period.