Identification and functional characterization of Glycosyl Hydrolase family 1 (GH1) genes acting on monolignol substrates in poplar and loblolly pine
Open Access
- Author:
- Sengupta, Anushree
- Graduate Program:
- Integrative Biosciences
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 07, 2011
- Committee Members:
- John Edward Carlson, Thesis Advisor/Co-Advisor
- Keywords:
- Lignin
lignin biosynthesis
glycosyl hydrolase family 1 (GH1)
&beta-glucosidase - Abstract:
- ß-glucosidases (BGLUs) are members of the Glycosyl hydrolase family 1 (GH1) group of enzymes that play important roles in several physiological processes in plants. Coniferin ß -glucosidase (CBG) identified by Dharmawardhana et al. (1995) in Pinus contorta was the first BGLU identified to specifically act on monolignol substrates. It removes a glucoside from the glucosylated form of coniferyl alcohol, coniferin, prior to its polymerization into lignin. Our goal is to try to identify the ß-glucosidase genes in poplar and pine that are specific to lignin monomers. We used the pine CBG cDNA sequence as BLAST query against all plant nodes in Phytozome (JGI) to identify other CBG genes and constructed a NJ tree with the sequences obtained manual sequence curation and 1000 bootstrap replicates with the aligned sequences. We retrieved 40 GH1 family genes from the Poplar genome and by phylogenetic analysis identified 6 Poplar genes that cluster with CBG and other lignin monomer specific genes, which includes two forms of the CBG gene in Pinus contorta and four forms of the gene in Pinus taeda identified previously in our lab (Song Liu, unpublished data). We analyzed the expression of the 6 genes identified to be putative lignification genes in the leaves, xylem and phloem samples collected during different time points in Populus balsamifera, a poplar species closely related to P. trichocarpa. Expression analysis of samples of xylem, phloem and leaves collected during April, June and September show a decrease in expression of the genes in from April to September in xylem and phloem. The expression is also higher in the vascular tissues where lignin is present than in the leaves.