Anisotropic diffuse growth in Arabidopsis stigma papillae

In angiosperms, the stigma is the first point of contact between the pollen (male) and pistil (female) during pollination. The stigma facilitates pollen capture and adhesion, compatibility responses, pollen germination, and pollen tube guidance to the transmitting tract. In Arabidopsis thaliana, the stigma is composed of single-celled stigma papillae that initiate from the apex of the carpels. Despite their critical function in plant reproduction, little is known about the cell and molecular mechanisms that govern stigma papillae growth and development. Using morphometric analysis of stigma papillae growth during different stages of floral development, we show that Arabidopsis stigma papillae grow via an anisotropic diffuse growth mechanism. Consistent with this conclusion, vegetative anisotropic growth mutants with defective microtubule and cellulose microfibril organization also have compromised stigma papillae growth.