SCAB3 Is Required for Reorganization of Actin Filaments during Light Quality Changes

The STOMATAL CLOSURE-RELATED ACTIN BINDING PROTEIN (SCAB) family is plant-specific, and its members all contain a novel actin binding domain. Here, we report that SCAB3, a homolog of SCAB1, binds, stabilizes and bundles actin filaments. The SCAB3 promoter contains a cis-element which could be bound by the FHY3/FAR1 transcription factors. Consistently, the expression of SCAB3 is induced when plants were transferred from white light to far red light (T-Far Red) conditions. The scab3 mutants show defects in the control of hypocotyl elongation under T-Far Red condition, which may result from an impaired reorganization of actin filaments. Together, our results suggest that SCAB3 plays an important role in plant growth under changes of light conditions possibly by regulating actin filament dynamics.