BIIDXI, a DUF642 cell wall protein, is involved in hypocotyl growth via auxin efflux

Auxin is involved in hypocotyl elongation in response to different environmental factors. BIIDXI is a cell wall DUF642 protein that participates in the regulation of the degree of pectin-methylesterification of the cell wall in different tissues, including hypocotyls. Under continuous light, bdx-1 seedlings presented longer hypocotyls than those of WT, while BIIDXI-overexpressed hypocotyls were auxin resistant. Auxin accumulation was observed in epidermal cells from bdx-1 hypocotyls, and the distribution pattern of PIN1 proteins differed. Moreover, the gravitropic response of bdx-1, a process that is highly dependent on auxin flux, was increased. In this study, we determined that BIIDXI is involved in hypocotyl elongation through the regulation of auxin flux.