8.A.175.  The Vasculature Complexity and Connectivity (VCC) Family

Arabidopsis VASCULATURE COMPLEXITY AND CONNECTIVITY (VCC) is a plant-specific transmembrane protein that controls the development of veins in cotyledons. Yanagisawa et al. 2021 showed that the expression and localization of PIN1 (TC# 2.A.69.1.1) is altered in vcc developing cotyledons, and that overexpression of PIN1-GFP partially rescues the vascular defects of vcc mutants. Genetic analyses suggested that VCC and PINOID (PID), a kinase that regulates PIN1 polarity, are both required for PIN1-mediated control of vasculature development. VCC expression is upregulated by auxin, likely as part of a positive feedback loop for the progression of vascular development. VCC and PIN1 localized to the plasma membrane in pre-procambial cells but were actively redirected to vacuoles in procambial cells for degradation. In the vcc mutant, PIN1 failed to properly polarize in pre-procambial cells during the formation of basal strands, and instead, it was prematurely degraded in vacuoles. VCC plays a role in the localization and stability of PIN1, which is crucial for the transition of pre-procambial cells into procambial cells that are involved in the formation of basal lateral strands in embryonic cotyledons (Yanagisawa et al. 2021).