Structural elucidation of hemicelluloses from oil-tea camellia fruit shell.

Oil-tea camellia fruit shell (CFS) is a very abundant waste lignocellulosic resource. The current treatments of CFS, i.e. composting and burning, pose a severe threat on environment. Up to 50 % of the dry mass of CFS is composed of hemicelluloses. However, chemical structures of the hemicelluloses in CFS have not been extensively studied, which limits their high-value utilization. In this study, different types of hemicelluloses were isolated from CFS through alkali fractionation with the assistance of Ba(OH)2 and H3BO3. Xylan, galacto-glucomannan and xyloglucan were found to be the major hemicelluloses in CFS. Through methylation, HSQC and HMBC analyses, we have found that the xylan in CFS is composed of →4)-ß-D-Xylp-(1→ and →3,4)-ß-D-Xylp-(1→ linked by (1→4)-ß glycosidic bond as the main chain; the side chains are α-L-Fucp-(1→, →5)-α-L-Araf-(1→, ß-D-Xylp-(1→, α-L-Rhap-(1→ and 4-O-Me-α-D-GlcpA-(1→, connected to the main chain through (1→3) glycosidic bond. The main chain of galacto-glucomannan in CFS consists of →6)-ß-D-Glcp-(1→, →4)-ß-D-Glcp-(1→, →4,6)-ß-D-Glcp-(1→ and →4)-ß-D-Manp-(1→; the side chains are ß-D-Glcp-(1→, →2)-ß-D-Galp-(1→, ß-D-Manp-(1→ and →6)-ß-D-Galp-(1→ connected to the main chain through (1→6) glycosidic bonds. Moreover, galactose residues are connected by α-L-Fucp-(1→. The main chain of xyloglucan is composed of →4)-ß-D-Glcp-(1→, →4,6)-ß-D-Glcp-(1→ and →6)-ß-D-Glcp-(1→; the side groups, i.e. ß-D-Xylp-(1→ and →4)-ß-D-Xylp-(1→, are connected to the main chain by (1→6) glycosidic bond; →2)-ß-D-Galp-(1→ and α-L-Fucp-(1→ can also connect to →4)-ß-D-Xylp-(1→ forming di- or trisaccharide side chains.

Identification and expression analysis of PUB genes in tea plant exposed to anthracnose pathogen and drought stresses.

The plant U-box (PUB) gene family, one of the major ubiquitin ligase families in plants, plays important roles in multiple cellular processes including environmental stress responses and resistance. The function of U-box genes has been well characterized in Arabidopsis and other plants. However, little is known about the tea plant (Camellia sinensis) PUB genes. Here, 89 U-box proteins were identified from the chromosome-scale referenced genome of tea plant. According to the domain organization and phylogenetic analysis, the tea plant PUB family were classified into ten classes, named Class I to X, respectively. Using previously released stress-related RNA-seq data in tea plant, we identified 34 stress-inducible CsPUB genes. Specifically, eight CsPUB genes were expressed differentially under both anthracnose pathogen and drought stresses. Moreover, six of the eight CsPUBs were upregulated in response to these two stresses. Expression profiling performed by qRT-PCR was consistent with the RNA-seq analysis, and stress-related cis-acting elements were identified in the promoter regions of the six upregulated CsPUB genes. These results strongly implied the putative functions of U-box ligase genes in response to biotic and abiotic stresses in tea plant.