MICROINJECTION OF POLLEN-SPECIFIC ACTIN-DEPOLYMERIZING FACTOR, ZMADF1, REORIENTATES F-ACTIN STRANDS IN TRADESCANTIA STAMEN HAIR-CELLS

Maize actin depolymerizing factor (ADF) binds both monomeric and filam entous actin and increases actin dynamics in vitro. To test its effect s in vivo, recombinant pollen ADF1 was expressed in bacteria and micro injected into Tradescantia stamen hair cells. Initially, all cytoplasm ic streaming ceased and the central, longitudinal transvacuolar strand s were disrupted. After 20-45 min, streaming resumed but in the form o f conspicuous transverse pathways of movement in the cortex. Staining the actin filaments by a second injection of fluorescein-conjugated ph alloidin showed that the longitudinal actin cables seen in controls ha d been replaced by a thickening of the transverse cortical arrays, who se orientation matched the new pattern of streaming. Microinjection of rhodamine-tubulin confirmed that the microtubules also formed a trans verse cortical array and it is suggested that the spatial cues for re- modelling the actin after ADF1. injection may be provided by the micro tubular system.