Rab-dependent vesicular traffic affects female gametophyte development in Arabidopsis

Rojek J., Tucker M.R., Pinto S.C., Rychłowski M., Lichocka M., Soukupova H., Nowakowska J., Bohdanowicz J., Surmacz G., Gutkowska M.

Keywords: Arabidopsis, auxin transport, female gametophyte, funiculus, ovule, PIN1, PIN3, Rab, rab geranylgeranyl transferase
Abstract: Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less atten-tion in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely dis-rupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased trans-port of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1ovules. These observations suggest that communication between the sporophyte and the developing female gameto-phyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.
DOI: 10.1093/jxb/eraa430
IEB authors: Hana Soukupová