Patterning of the inflorescence – What is the biological process that gives rise to it?
Two factors: branchiness and determinacy underlie all major inflorescence types
- The gene LEAFY (LFY) inhibits branchiness (the “one stalk gene”). [N.B. LFY = FLO in Antirrhinum]. (If LFY is strongly expressed it produces one stalk, down-regulation of LFY gives branching.)
- The gene TERMINAL FLOWER1 (TFL1) promotes indeterminacy (the “ever growing gene”). [N.B. TFL1 = CEN in Antirrhinum, SP in tomato]. When TFL1 is strongly over-expressed in transgenic lines of tobacco, the inflorescence grows and grows (forever?)
*Remember genes are named for the knock-out mutants. The Terminal Flower mutant results in determinate growth of inflorescence.
Differential expression of LFY and TFL1 sufficient to explain much of all major patterns of inflorescence architecture through control of determinacy and branching. In a notable paper a mathematical model was developed to examine the role of LFY and TFL1. A wide variety of inflorescences could be theoretically explained by regulation of these two genes. For example, down-regulation of TFL1 caused increase in inflorescence determination while down regulation of LFY caused an increase in branching. Combination of different activities of LFY and TFL1 would result in a diversity of patterns.