RNA recognition motifs as important regulators of gene expression are highly conserved in animals and plants. The FCA floral promotion gene in Arabidopsis encodes a protein, containing two RNA recognition motifs (RRM) and a WW protein interaction domain. Here we isolated FCA cDNA from rice. FCA in rice (rFCA) was homologous to FCA-gamma of Arabidopsis and contained conserved domains. To investigate the function of RRM domain, fragment RRM1 and RRM2 of rFCA were introduced into rice subspecies Oryza sativa L. subsp. Indica var. 9311 and another rice subspecies Oryza sativa L. subsp. Japonica var. zhonghua11 transformation. Two transgenic lines exhibited similar phenotypes, flowering time delay, seed size and cell volume of transgenic plants was increased. These results showed that constitutive expression of RRMs could regulate cellular size. The patterns of overexpression of two RRM domains and their similar morphologies indicate they may play a same role.

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