Alterations of F-actin cytoskeleton during incompatible pollen rejection in Nicotiana alata

JUAN A ROLDÁN; ARIEL GOLDRAIJ

Puerto Madryn, Chubut

Congreso; XLVI Reunión anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Alterations of F-actin cytoskeleton during incompatible pollen rejection in Nicotiana alata Juan A Roldán and Ariel Goldraij CIQUIBIC–CONICET Dpto. Química Biológica, Facultad de Cs. Químicas, Universidad Nacional de Córdoba. The integrity of F-actin cytoskeleton is essential for polar growth in pollen tubes. So far, most studies of F-actin organization in pollen tubes were carried out on in vitro cultured pollen tubes. We studied the in vivo changes of F-actin during rejection of incompatible pollen tubes of Nicotiana alata. Compatible pollen tubes reached the ovary 72 h after pollination while incompatible ones were full stopped at fifth day after pollination, slightly below the middle style. Early after pollination about 70% of both compatible and incompatible pollen tubes showed an organized pattern of F-actin long cables along the main axis of the cell. The remaining tubes exhibited an altered pattern consisting of isolated fragments or punctate foci of F-actin. While these proportions were kept constant in compatible pollinations throughout the style, incompatible pollinations showed a progressive decrease of F-actin integrity of pollen tubes. Five days after pollination, 70% of incompatible pollen tubes showed a disorganized pattern of F-actin. We are studying if alteration of F-actin in incompatible pollen tubes preceeds the S-RNase releasing from vacuole to cytoplasm, the crucial step in Nicotiana pollen rejection. If so, incompatible pollen rejection would occur in two steps: a) F-actin disruption to stop growth and b) pollen RNA degradation and subsequent cell death.