| dc.description.abstract | The branching or tillering of crops is an important agronomic trait with a major
impact on yield. Maintaining an appropriate number of branches allows the plant to use
limited light resources and to produce biomass or yield more effectively. The branching
process includes the initiation of the axillary meristem leading to bud formation and the
further outgrowth of the axillary buds. Phytohormones, including cytokinins and auxin,
are known to play major roles in regulating axillary bud outgrowth.
Light signals, including light quantity and light quality, are among the most
important factors regulating plant growth and are perceived by the action of specialized
photoreceptors, including phytochromes. Phytochromes sense red (R) and far-red (FR)
light and allow some plants to perceive and respond to competing neighbors by evoking
the shade avoidance syndrome (SAS). One component of the SAS is inhibition of
branching. Phytochrome B (phyB) is especially important in sensing shade signals and
loss of phyB function results in a constitutive shade avoidance phenotype, including
reduced branching. While it has been anecdotally reported that phyB-deficient
Arabidopsis branches less than wild type, a detailed study of the defects in the process is
lacking. In this research, the interactions between light signals, phytochromes and phytohormones in the regulation of branching were assessed using an integrated
physiological, molecular and genetic approach. | en |
