Plant responses to ultraviolet-B (UV-B:280-320nm) stress: What are the key regulators?
2000
Mackerness, S.A.H.
Depletion of the stratospheric ozone layer is leading to an increase in ultraviolet-B (UV-B: 280-320 nm) radiation reaching the earth's surface. This has raised interest in the possible consequence of increased UV-B levels on plant growth and development and the mechanisms underlying these responses. Although the effects of UV-B are now well characterised at the physiological level, little is known about the cellular and molecular mechanisms involved. Recent studies have shown that UV-B affects a number of important physiological processes, such as photosynthesis, through effects on gene expression. In addition, induction of a number of defense mechanisms, such as production of UV-B screening pigments, increase in antioxidant enzymes and induction of pathogenesis-related proteins, are also mediated at the level of gene expression. The signal transduction pathways by which UV-B regulates gene expression are at present poorly understood. The studies carried out to date, however, indicated a pivotal role for reactive oxygen species as key second messengers acting up-steam of a number of pathways involving the plant hormones salicylic acid, jasmonic acid and ethylene. The transduction pathways identified to date and the role of intermediates in regulating tolerance to UV-B damage are discussed in this review.
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