Photomorphogenesis: Light receptor kinases in plants!

Because plants use light energy in photosynthesis, they are extremely sensitive to their light environment. Light affects plants throughout their life cycle, during processes such as seed germination, seedling and vegetative development and the transition to flowering [1]. Plants are sensitive to the quality, quantity, duration and direction of light [1], and to achieve this sensitivity they are armed with a battery of photoreceptors. For example, photoreceptors that detect UV-B light — not yet molecularly characterized — are important for seedling development in response to low doses of UV-B light [2]. Two classes of photoreceptors detect UV-A and blue light: cryptochromes (CRY1 and CRY2) and a photoreceptor known by its gene name as ‘non-phototropic hypocotyl 1’ (NPH1). The former play major roles during seedling development and the transition to flowering, whereas the latter is required for directional growth towards a light source (phototropism) [3,4]. Phytochromes are a class of red/farred photoreceptors — five types, phytochromes A to E, have been defined in Arabidopsis — that affect all aspects of plant development; they also play accessory roles in UV-B and blue-light sensing [2,5].