Mutation in sorghum <i>LOW GERMINATION STIMULANT 1</i> alters strigolactones and causes <i>Striga</i> resistance

Abstract

<i>Striga</i> is a major biotic constraint to sorghum production in semiarid tropical Africa and Asia. Genetic resistance to this parasitic weed is the most economically feasible control measure. Mutant alleles at the <i>LGS1</i> (<i>LOW GERMINATION STIMULANT 1</i>) locus drastically reduce <i>Striga</i> germination stimulant activity. We provide evidence that the responsible gene at <i>LGS1</i> codes for an enzyme annotated as a sulfotransferase and show that functional loss of this gene results in a change of the dominant strigolactone (SL) in root exudates from 5-deoxystrigol, a highly active <i>Striga</i> germination stimulant, to orobanchol, an SL with opposite stereochemistry. Orobanchol, although not previously reported in sorghum, functions in the multiple SL roles required for normal growth and environmental responsiveness but does not stimulate germination of <i>Striga</i> This work describes the identification of a gene regulating <i>Striga</i> resistance and the underlying protective chemistry resulting from mutation.