Light is one of the most important environmental signals regulating a wide range of physiological and developmental processes in plants, from seed germination to flowering. To perceive changes in the light, plants evolved photoreceptors specialized in absorbing light of different wavelengths. Phytochromes are the red/far-red light-absorbing photoreceptors of plants. Phytochromes (phyA-phyE) control responses throughout the plant life like seed germination, seedling de-etiolation, shade avoidance and transition of flowering. PhyA and phyB are the most prominent phytochromes to mediate photo-morphogenesis under normal conditions and phyB has major role to control light responses in mature, de-etiolated plants. To date, little is known about phyB mediated signalling cascade, however, clear evidences show that a specific set of genes are regulated by phyB-signalling. Light induces nuclear import of phy (A-E) and formation of phytochrome-containing nuclear protein complexes termed speckles or nuclear bodies (NBs). Although the precise function of NB formation is unknown, it is tempting to speculate that NBs are closely associated with phyB signalling. The project aims to unravel the link between phyB-NB formation and phyB signalling. I would like to purify and determine the components of phyB containing subnuclear complexes from Arabidopsis thaliana using tandem affinity purification (TAP) method and mass spectrometry. After determination of NB complexes, the biological function of identified protein components would be examined on multi-level from plant physiology to molecular biology. As we expect, we can uncover new factors and downstream steps of phyB mediated red-light signalling pathway after NB formation. Determination of phyB-signalling complex could also help us for better understanding the cross-talk between other signalling pathways.
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