AN ANION CHANNEL IN ARABIDOPSIS HYPOCOTYLS ACTIVATED BY BLUE-LIGHT

A rapid, transient depolarization of the plasma membrane in seedling s tems is one of the earliest effects of blue light detected in plants, it appears to play a role in transducing blue light into inhibition of hypocotyl (stem) elongation, and perhaps other responses. The possibi lity that activation of a Cl- conductance is part of the depolarizatio n mechanism was raised previously and addressed here, By patch clampin g hypocotyl cells isolated from dark-grown (etiolated) Arabidopsis see dlings, blue light was found to activate an anion channel residing at the plasma membrane. An anion-channel blocker commonly known as NPPB [ 5-nitro-2-(3-phenylpropylamino)-benzoic acid] potently and reversibly blocked this anion channel, NPPB also blocked the blue-light-induced d epolarization in vivo and decreased the inhibitory effect of blue ligh t on hypocotyl elongation, These results indicate that activation of t his anion channel plays a role in transducing blue light into growth i nhibition.