Root system depth is shaped by EXOCYST70A3 via modulation of auxin transport (Cell)

The angle at which roots grow into the soil is modulated by the interaction between genetics and environment, and involves the gravity perception and response pathways including auxin transporters. Ogura et al. did a GWAS analysis of the gravitropic response of different Arabidopsis accessions in the presence of the auxin-transport inhibitor NPA, and identified allelic variation in EXOCYST70A3, encoding an exocytosis factor, as involved in root response to NPA. Specifically, perturbation of EXO70A3 expression regulates PIN4 levels and patterns in root columella cells, hence auxin distribution. In plants grown in pots, allelic variation or altered expression of EXO70A3 affected root system architecture. Furthermore, one of the naturally occurring haplotypes contributed to higher seed set under drought conditions. As part of a larger effort, this gene can contribute to efforts to engineer deep, carbon-storing roots to slow the rate of anthropomorphic climate change. (Summary by Mary Williams) Cell 10.1016/j.cell.2019.06.021