ABSTRACT
Photosynthesis is a key component of plant biology. It is an essential driver of primary carbohydrate biosynthesis and other aspects of metabolism such as the assimilation of nitrogen into organic compounds within the chloroplast (Blankenship 2002; Forde and Lea 2007). Photosynthesis is a sophisticated process involving complex bioenergetics and a wide range of different molecules, such as proteins, lipids, and light absorbing chromophores. Photosynthesis is therefore sensitive to regulation and perturbation by biotic and abiotic stimuli. One major abiotic environmental stimulus is UVB radiation (280–315 nm), which is a typical component of the light environment. UVB wavelengths are frequently absorbed by component molecules of photosynthesis (Strid et al. 1990, 1994; Jordan 1996), and such wavelengths have the potential to initiate loss of function and a cascade of damaging consequences, such as the production of reactive oxygen species (ROS) (Mackerness et al. 1999b). UVB is readily absorbed by DNA, causing damaging lesions (Jordan 1996; Taylor et al. 1996). In addition, UVB regulates non-specific changes to gene expression and also acts through a specific photoreceptor molecule that can alter gene expression (see below). In terms of photosynthesis itself, there is a requirement for substantial gene expression activity to establish the complex biostructure of the chloroplast (with its contrasting soluble and membrane components) and to maintain component parts by constant turnover, for example, D1 and D2 polypeptide production. Overall, there is substantial potential for UVB-mediated changes to the photosynthetic process.
