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Regulation Of Light- And Circadian-Associated Plant Developmental Processes

Impacts addressed:

The life cycle of higher plants consists of two major phases the vegetative phase and the reproductive (flowering) phase. In general plants store matter and energy in the form of carbohydrate reserves during the vegetative phase and then mobilize these reserves in the development of flowers fruit and seeds during the reproductive phase which is often triggered by various light- and circadian-related factors. As a consequence of this the timing of the transition to flowering can significantly affect the biomass yields of vegetative structures (leaves stems and roots) and reproductive structures. Hence the ability to control the timing of plant flowering could have important applications in agriculture horticulture and forestry. Researchers at the University of California have isolated an Arabidopsis gene known as CCA1 that encodes a regulatory transcription factor involved in light- and circadian-regulated gene expression. The UC researchers have shown that CCA1 plays an important role in plant development notably that overexpression of the gene in transgenic plants causes delayed flowering. These plants also display reduced sensitivity to photoperiod for their growth and development and have elongated stems. Transgenic plants incorporating CCA1 might have a number of advantages over wild-type plants such as a lengthened harvesting season for vegetables and fruits or lengthened vegetative phases with higher yields for vegetables such as spinach and cabbage. Further light requirements might be rendered less stringent to extend the growing range of photoperiodic plants. The UC researchers have also isolated a protein kinase regulatory subunit called CKB2 which stimulates the transcriptional activity of CCA1 proteins. CKB2 does so both by inducing protein-binding and by protein-activation (via phosphorylation) thus strongly modulating CCA1-mediated transcription. Thus CKB2 provides an alternative to CCA1 for genetic engineering of plants to control light- and circadian-associated plant developmental processes.

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