Strigolactone inhibition of shoot branching
Abstract
A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactones
are compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds and
stimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of pea
are strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants.
Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibition
signal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis.
In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots and
act at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching in
plants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizal
symbiosis and parasitic weed interaction.