Amelioration of ultraviolet-B-induced down-regulation of mRNA levels for chloroplast proteins, by high irradiance, is mediated by photosynthesis

• Published in: Journal of plant physiology 1996, Vol.148 (1-2), p.100-106
• Main Authors: MACKERNESS, S. A.-H, BUTT, P. J, JORDAN, B. R, THOMAS, B
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Fundamental and applied biological sciences. Psychology; Pisum sativum
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/S0176-1617(96)80300-2

The mechanism by which increasing photosynthetically active radiation (PAR) reduces the sensitivity of RNA transcripts to UV-B radiation was studied in pea (Pisum sativum L.). mRNA transcript levels for rbc S, rbc L, cab and psb A were measured over an 8 d experimental period in pea plants supplemented with UV-B radiation under a range of conditions. Under low light (150 mu mol m super(-2)s super(-1)), UV-B resulted in a significant decline in the levels of transcripts for all four genes which was prevented by increasing the background irradiance to 350 mu mol m super(-2)s super(-1) (high light) with white light from fluorescent lamps. Increasing CO sub(2) levels to give photosynthesis rates equivalent to the high light treatment partially protected rbc L and cab transcripts and fully protected rbc L transcripts but did not prevent visible injury. Increasing light with low pressure sodium lamps, which increase photosynthesis but are not effective for activation of the DNA repair enzyme, photolyase, gave results which were not significantly different from white fluorescent high light treatments. Protection by high light was lost in the presence of the photosynthesis inhibitors CCCP and DCMU. The UV-B induced increase in the expression of chalcone synthase (chs) genes was delayed by the treatments which increased photosynthesis rates and conferred protection. The results indicate that photosynthesis plays a key role in the amelioration of UV-B induced decline in mRNA levels for proteins. The minimal role of DNA repair by photolyase indicates that reduction in photosynthesis gene transcripts in response to UV-B represents a specific regulation rather than being a consequence of DNA damage.