A Small Guanosine Triphosphate Binding Protein Promotes Xylem Development in Poplar.

Rab GTPases are the subfamily of the small guanosine triphosphate (GTP)-binding proteins which participated in the regulation of various biological processes. Recent studies have found that plant Rabs play some specific functions. However, the functions of in xylem development in trees remain unclear. In this study, functional identification of in was performed. Quantitative reverse transcription PCR (qRT-PCR) results showed that was highly accumulated in stems, especially in phloem and xylem tissues. Overexpression of in poplar enhanced programmed cell death (PCD) and increased the growth rate and the secondary cell wall (SCW) thickness. Quantitative analysis of monosaccharide content showed that various monosaccharides were significantly increased in secondary xylem tissues of the overexpressed lines. Flow cytometry analysis revealed that the number of apoptotic cells in lines is more than a wild type (WT), which indicated that may play an important role in PCD. Further studies showed that overexpression of increased the expression level of genes involved in SCW biosynthesis, PCD, and autophagy. Collectively, the results suggest that plays a positive role in promoting the xylem development of poplar.