PHOTOSENSORY PERCEPTION AND SIGNAL-TRANSDUCTION IN HIGHER-PLANTS - MOLECULAR-GENETIC ANALYSIS

Light plays a crucial role throughout the life cycle of higher plants modulating various aspects of their growth and development, such as se ed germination, leaf differentiation, flowering, and senescence. Plant s have thus evolved extremely sensitive mechanisms to continually dete ct the changing ambient light conditions and transduce the information to the gene expression machinery. The elucidation of this complex inf ormation sensing and transduction machinery is fundamental to our unde rstanding of the molecular mechanisms involved in light-regulated plan t development. The last decade has witnessed an immense upsurge in inf ormation in this regard and the mechanism of photosensory perception a nd phototransduction is turning out to be quite intricate, involving a n array of cellular effecters and biochemical messengers. The analysis of photomorphogenic mutants, predominantly of Arabidopsis, has reveal ed interesting facts, not only about the intricacies of light signalin g circuitry, but also about the multiplicity of the photoreceptors and their specialized or overlapping photosensory functions. In addition, these studies have also highlighted, and in some cases even redefined , the role of conventional plant growth regulators in modulating photo morphogenic development. Employing standard recombinant DNA techniques , substantial information has also become available about the regulato ry cis-acting DNA sequences that make a gene amenable to light control and the trans-acting protein factors that can potentially interact wi th these cis-acting sequences on receiving the signal from the upstrea m transduction components. The information available to date on these emerging trends in photomorphogenesis research has been summarized and critically evaluated in this review.