The GDP-mannose transporter gene (DoGMT) from Dendrobium officinale is critical for mannan biosynthesis in plant growth and development

Abstract Dendrobium officinale is a precious traditional Chinese medicinal herb because it is abundant in mannose-containing polysaccharides (MCPs). GDP-mannose transporter (GMT), which translocates GDP-mannose into the Golgi lumen, is indispensable for the biosynthesis of MCPs. In this study, we found that the dominant polysaccharides in D. officinale were MCPs in a range of varieties and different physiological phases. After a positive correlation between the accumulation of mannose and the transcript levels of candidate GMT genes was found, three GMT genes ( DoGMT1-3 ) were identified in D. officinale . DoGMT1 , DoGMT2 and DoGMT3 exhibited the highest transcript level in stem that an organ for MCPs storage. All three DoGMT proteins were targeted to Golgi apparatus, and had a GDP binding domain (GXL/VNK) that was homologous to a specially characterized GMT protein GONST1 in Arabidopsis thaliana . Moreover, DoGMT1 , DoGMT2 and DoGMT3 complemented a GDP-mannose transport-defective yeast mutant ( vrg4-2 ), meanwhile they also demonstrated a higher GDP-mannose uptake activity. Therefore, we conclude that DoGMT1 , DoGMT2 and DoGMT3 are able to transport GDP-mannose while the expression patterns of these genes correspond to the accumulation of MCPs in D. officinale . These findings support the importance of GMT genes from D. officinale in the biosynthesis of MCPs.