Molecular characterization of NbCHMP1 encoding a homolog of human CHMP1 in Nicotiana benthamiana

In humans, CHMP1 encodes a protein of dual function that plays a role in both modification of chromatin structure and endosomal vesicle trafficking. Recently, it was found that sal1, a CHMP1 homolog in maize, is important for the development of the aleurone cell layers in maize endosperm. In this study, we investigated the structure and function of a Nicotiana benthamiana CHMP1 homolog designated NbCHMP1. NbCHMP1 encodes a small protein with a bipartite nuclear localization signal at its N-terminus, and good homology with the corresponding genes from diverse plants and animals. NbCHMP1 mRNA was present at comparable levels in stems, roots, flowers, and leaves. A GFP fusion of the full length NbCHMP1 protein was localized to the cytosol in distinct structures, while a GFP fusion of its N-terminal 80 aa was targeted to the nucleus, suggesting dual-targeting of NbCHMP1 in plants. Overexpression of NbCHMP1 in yeast did not affect its growth and the expressed protein was present in the cytosol in particulate form. Virus-induced gene silencing of NbCHMP1 resulted in subtle alterations of leaf morphology and color, without significantly affecting plant viability or development. Thus the CHMP1 homolog apparently does not play an essential role in the development of the vegetative tissues of N. benthamiana, in contrast to the essential role of sal1 in formation of the aleurone cell layers during maize endosperm development.