Members of the Arabidopsis FORKED1-LIKE gene family act to localize PIN1 in developing veins.

The reticulate leaf vein pattern typical of angiosperms is proposed to have been a driving force for their evolutionary success. Vein pattern is established through auxin canalization via the auxin efflux protein PINFORMED1 (PIN1). During formation of vein loops, PIN1 cellular localization is increasingly restricted to either the basal side of cells in the lower domain or to the apical side in the upper domain.

Localization of Arabidopsis FORKED1 to a RABA-positive compartment suggests a role in secretion.

When FORKED1 (FKD1) is mutated, asymmetric localization of PINFORMED1 (PIN1), particularly to the apical side of cells, fails to occur properly in developing veins, resulting in an open vein pattern. FKD1 encodes a protein with a Pleckstrin homology-like (PL) domain, suggesting interaction with phosphoinositides. FKD1 has been previously found to interact with an ADP ribosylation factor GTPase-activating protein (ARF-GAP) important for vein patterning, SCARFACE/VAN3 (SFC).