Os07g0596300

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Annotated Information

Function

Formin Homology 5(FH5), a type II formin-like protein encoded by Rice Morphology Determinant (RMD), functions as an actin-nucleating protein that regulates rice plant morphology by modulating the microtubule- and microfilament-based cytoskeletal systems. Biochemical assays demonstrated that recombinant FH5 protein can nucleate actin polymerization from monomeric G-actin or actin/profilin complexes, cap the barbed end of actin filaments, and bundle actin filaments in vitro. Moreover, FH5 can directly bind to and bundle microtubules through its FH2 domain in vitro. The rice formin protein FH5 plays a critical role in determining plant morphology by regulating actin dynamics and proper spatial organization of microtubules and microfilaments.

Expression

FH5/RMD encodes a formin-like protein consisting of an N-terminal phosphatase tensin (PTEN)-like domain, an FH1 domain, and an FH2 domain. FH5/RMD is ubiquitously expressed in rice tissues, and its protein localization to the chloroplast surface is mediated by the PTEN domain. Formins are known to be morphoregulatory proteins that direct the assembly of unbranched actin filaments in eukaryotes such as fungi, animals, and plants (Paul and Pollard, 2009). Most formins have two highly conserved domains, the Pro-rich domain(i.e., formin homology 1 [FH1]) and the formin homology domain(i.e., FH2).Plant formins are grouped into two subfamilies, type I and type II. Type I formins contain an N-terminal transmembrane domain,which is believed to be involved in the association of formin proteins with the plasma membrane, whereas this feature is absent from type II formins (Cvrckova´ et al., 2004). Some plant type II formins have an N-terminal phosphatase tensin (PTEN)- like domain, which was suggested to play a role in mediating localization of the protein to the apical side of the cells in the moss Physcomitrella patens (Vidali et al., 2009).

Mutation

The rmd mutants display a bending growth pattern in seedlings, are stunted as adult plants, and have aberrant inflorescence (panicle) and seed shape. Cytological analysis showed that rmd mutants have severe cell elongation defects and abnormal microtubule and microfilament arrays.

Compared with wild-type plants, rmd mutants exhibited changed architecture in both vegetative and reproductive phases.

rmd Mutants Display Severe Defects in Cell Elongation

and Impaired in Microfilament Organization

,Display Defective Microtubule Organization

Labs working on this gene

School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, China Michigan State University–Department of Energy Plant Research Laboratory, Michigan State University, East Lansing,Michigan 48824 Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824

References

Zheng Zhang, Yi Zhang, Hexin Tan, Ying Wang, Gang Li,Wanqi Liang, Zheng Yuan, Jianping Hu, Haiyun Ren,and Dabing Zhanga.(2011)RICE MORPHOLOGY DETERMINANT Encodes the Type II Formin FH5 and Regulates Rice Morphogenesis.The Plant Cell.