January 9-13, 2010
Town & Country Convention Center
San Diego, CA
Srirama R. Krishnareddy1 , Jorge J. Casal2 , Scott A. Finlayson1
The branching habit of plants is a key determinant of overall plant form and function with great relevance to modern agriculture. Shade signals (red light:far red light [R:FR]) transduced by phytochromes are major regulators of axillary bud outgrowth, and through this mechanism control branching in both natural and agricultural environments. Our recent work in Arabidopsis demonstrates that light signals perceived by phytochromes control the timing of the release of bud outgrowth, the subsequent rate of bud elongation and the coordination of bud outgrowth between buds at different positions. Furthermore, analysis of candidate gene mRNA abundances indicates that light signals regulate the expression of the branching integrators BRC1 and BRC2, which are associated with distinct gene networks and branching processes. To investigate the regulation of branching by R:FR in more detail, we have developed a system using supplemental FR LEDs to tightly control the outgrowth of Arabidopsis axillary buds. Depending on the position of the bud in the rosette, outgrowth is either repressed or rapidly promoted by high R:FR. AtH1 microarray transcriptome analysis was conducted using axillary buds showing repression or promotion of outgrowth in response to high R:FR. Changes in gene expression revealed patterns associated with light signal transduction and processes related to the activation of bud outgrowth and provide much needed data to allow the testing of additional hypotheses related to the phenomenon.