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Cloning and Expression Analysis of Two Sitosterol Glycosyltransferase Genes in Populus tomentosa
Li Siyan1, Guo Bin2, An Xinmin1*
1National Engineering Laboratory for Tree Breeding, NDRC, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, MOE, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China; 2Shanxi Academy of Forestry, Taiyuan 030012, China
Abstract: Sitosterol glycosyltransferase (SGT) is a glycosyltransferase that catalyzes the glycosylation of plant sitosterol with membranes. The sitosterol-glucoside (SG) can act as a primer for cellulose synthesis under the action of cellulose synthase (CesA) and forms glucan chains using UDP-glucose as a substrate. In order to study the function of PtSGT gene in Populus tomentosa， PCR primers were designed according to the homologous genes PtrSGT1 and PtrSGT3 of Populus trichocarpa. The cDNA sequences of PtSGT1 and PtSGT3 CDS were cloned from cDNAs of P. tomentosa seedlings， and their lengths were 1 851 bp and 1 911 bp， encoding 616 and 636 amino acids， respectively. Structural analysis showed that the homologous genes PtrSGT1 and PtrSGT3 of P. trichocarpa contained 14 exons and 13 introns， with significant differences in structure and length， and were located on chromosomes 14 and 2， respectively. Amino acid sequence homology analysis and phylogenetic analysis showed that PtSGT1 and PtSGT3 have high homology with P. trichocarpa and Populus euphratica. The results of Real-time PCR showed that all genes in the PtSGT gene family were expressed in roots， stems and leaves， with a constitutive expression pattern overall. The relative expression of PtSGT3 was higher than other 3 members in poplar tissues， the highest expression in stems. It was speculated that PtSGT3 played an important role in the synthesis of sitosterolglucoside. The results of this experiment laid a foundation for further analysis of the functions of these two genes in cellulose synthesis of P. tomentosa.
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