Identification and Characterization of Tomato SWI3-Like Proteins: Overexpression of SlSWIC Increases the Leaf Size in Transgenic Arabidopsis

As the subunits of the SWI/SNF (mating-type switching (SWI) and sucrose nonfermenting (SNF)) chromatin-remodeling complexes (CRCs), Swi3-like proteins are crucial to chromatin remodeling in yeast and human. Growing evidence indicate that AtSWI3s are also essential for development and response to hormones in Arabidopsis. Nevertheless, the biological functions of Swi3-like proteins in tomato (Solanum lycopersicum) have not been investigated. Here we identified four Swi3-like proteins from tomato, namely SlSWI3A, SlSWI3B, SlSWI3C, and SlSWI3D. Subcellular localization analysis revealed that all SlSWI3s are localized in the nucleus. The expression patterns showed that all SlSWI3s are ubiquitously expressed in all tissues and organs, and SlSWI3A and SlSWI3B can be induced by cold treatment. In addition, we found that SlSWI3B can form homodimers with itself and heterodimers with SlSWI3A and SlSWI3C. SlSWI3B can also interact with SlRIN and SlCHR8, two proteins involved in tomato reproductive development. Overexpression of SlSWI3C increased the leaf size in transgenic Arabidopsis with increased expression of GROWTH REGULATING FACTORs, such as GRF3, GRF5, and GRF6. Taken together, our results indicate that SlSWI3s may play important roles in tomato growth and development.