Formin Mediated Actin Cytoskeleton Organization

---Not Only for Tip-growth

The actin cytoskeleton is an important regulator of cell expansion and morphogenesis in plants. Formins have been found to exist in many eukaryotic organisms including animals, fungi and plants, and are involved in many fundamental cellular processes including cytokinesis, cell motility and polarity by regulation of actin dynamics. Previous studies of actin in plants mainly focused on tip growth of pollen tubes and root hairs. My recent work identified a Class II formin BUI1 (BENT UPPERMOST INTERNODE1) in rice and found that BUI1 could modulate actin dynamics and cell polar expansion.

BUI1 encodes the class II formin FH5. Mutation of BUI1 results in severely disruption of the actin cytoskeleton and consequently inhibition of cell expansion. In collaboration with Dr. HUANG Shanjin’ group from the Institute of Botany, CAS, we dissected the biochemical functions of BUI1 and found that BUI1 could efficiently promote actin filament assembly and actin bundling. Thus, our study identified a rice formin protein BUI1 that regulates de novo actin nucleation and spatial organization of the actin filaments, which are important for proper cell expansion and rice morphogenesis. The identification of BUI1 also reveals a new regulatory mechanism underlying the development of rice internodes.

Link: Plant Cell 2011 23: 661-680. First Published on February 9, 2011; doi:10.1105/tpc.110.081802

BENDED UPPERMOST INTERNODE1 Encodes a Class II Formin Critical For Actin Dynamics and Rice Development

(A) Wild type (Zhejing 22) (left) and bui1 (right) plants.

(B) Panicle exsertion of wild type (the left one) and bui1 (the right three).

(C) and (D) Longitudinal sections of the uppermost internodes of the wild type (C) and bui1 (D) at heading stage.

(E) and (F) F-actin organization in the root elongation region cells of the wild type (E) and bui1 (F).

(G) and (H) BUI1 promotes profilin/Oregon-green-actin polymerization.