Here, we investigated the role of auxin distribution in controlling Arabidopsis thaliana late stamen development. We analysed auxin distribution in anthers by monitoring DR5 activity: at different flower developmental stages; inhibiting auxin transport; in the rpk2-3 and ems1 mutants devoid of middle layer (ML) or tapetum, respectively; and in the auxin biosynthesis yuc6 and perception afb1-3 mutants. We ran a phenotypic, DR5::GUS and gene expression analysis of yuc6rpk2 and afb1rpk2 double mutants, and of 1-N-naphthylphthalamic acid (NPA)-treated flower buds. We show that an auxin maximum, caused by transport from the tapetum, is established in the ML at the inception of late stamen development. rpk2-3 mutant stamens lacking the ML have an altered auxin distribution with excessive accumulation in adjacent tissues, causing non-functional pollen grains, indehiscent anthers and reduced filament length; the expression of genes controlling stamen development is also altered in rpk2-3 as well as in NPA-treated flower buds. By decreasing auxin biosynthesis or perception in the rpk2-3 background, we eliminated these developmental and gene expression anomalies. We propose that the auxin maximum in the ML plays a key role in late stamen development, as it ensures correct and coordinated pollen maturation, anther dehiscence and filament elongation.
Arabidopsis Arabidopsis Proteins