Comparative proteomic analysis of thick-walled ray formation of Haloxylon ammodendron in the Gurbantunggut Desert, China
Abstract Background The thick-walled ray cells have been reported in Haloxylon ammodendron for the first time. This study measured the wall thickness of ray cells and performed a proteomic analysis of ray cell wall formation in the xylem of H. ammodendron using isobaric tags for relative and absolute quantitation. Results The wall thickness of ray cells in Jinghe (2.85 ± 0.42 µm) was significantly lower than that in Shihezi (3.08 ± 0.44 µm) (P < 0.01). In Shihezi, which has a thicker wall of ray cells than that in Jinghe, 795 differentially expressed proteins were upregulated. Phenylpropanoid biosynthesis, photosynthesis, glycolysis/gluconeogenesis, carbon metabolism, starch and sucrose metabolism, metabolic pathways, etc. promote ray cell wall biosynthesis of the xylem of H. ammodendron by providing substrates or energy. During the process of cell wall biosynthesis in the xylem of H. ammodendron, the nonspecific lipid-transfer protein and beta expansin EXPB2.1 (Mirabilis jalapa] first loosens the cell wall, followed by extension and expansion, and the xyloglucan endotransglycosylase/hydrolase 1 cleaves and links the xyloglucan chains. Then, photosystem I P700 apoprotein A1, reversibly glycosylated polypeptide 1 and GDP-mannose-3′, 5′-epimerase, etc., are involved in cellulose, hemicellulose and pectin biosynthesis of the cell wall by providing components or energy. Finally, the proteins in phenylpropanoid biosynthesis promote the lignification of the ray cell wall and complete the biosynthetic process of the cell wall. Conclusions Phenylpropanoid biosynthesis, photosynthesis, glycolysis/gluconeogenesis, carbon metabolism, starch and sucrose metabolism, metabolic pathways, etc. promote ray cell wall biosynthesis of the xylem of H. ammodendron by providing substrates or energy. The results are important for improving the wood mechanical properties of timber plantations.
