Key Laboratory of National Forestry and Grassland Administration/Beijing for Bamboo & Rattan Science and Technology, Institute of Gene Science and Industrialization for Bamboo and Rattan Resources, International Center for Bamboo and Rattan, Beijing, 100102, China.
BMC Genomics. 2021 Dec 2;22(1):867. doi: 10.1186/s12864-021-08192-y.
Xylan is one of the most abundant hemicelluloses and can crosslink cellulose and lignin to increase the stability of cell walls. A number of genes encoding glycosyltransferases play vital roles in xylan biosynthesis in plants, such as those of the GT43 family. However, little is known about glycosyltransferases in bamboo, especially woody bamboo which is a good substitute for timber.
A total of 17 GT43 genes (PeGT43-1 ~ PeGT43-17) were identified in the genome of moso bamboo (Phyllostachys edulis), which belong to three subfamilies with specific motifs. The phylogenetic and collinearity analyses showed that PeGT43s may have undergone gene duplication, as a result of collinearity found in 12 pairs of PeGT43s, and between 17 PeGT43s and 10 OsGT43s. A set of cis-acting elements such as hormones, abiotic stress response and MYB binding elements were found in the promoter of PeGT43s. PeGT43s were expressed differently in 26 tissues, among which the highest expression level was found in the shoots, especially in the rapid elongation zone and nodes. The genes coexpressed with PeGT43s were annotated as associated with polysaccharide metabolism and cell wall biosynthesis. qRT-PCR results showed that the coexpressed genes had similar expression patterns with a significant increase in 4.0 m shoots and a peak in 6.0 m shoots during fast growth. In addition, the xylan content and structural polysaccharide staining intensity in bamboo shoots showed a strong positive correlation with the expression of PeGT43s. Yeast one-hybrid assays demonstrated that PeMYB35 could recognize the 5' UTR/promoter of PeGT43-5 by binding to the SMRE cis-elements.
PeGT43s were found to be adapted to the requirement of xylan biosynthesis during rapid cell elongation and cell wall accumulation, as evidenced by the expression profile of PeGT43s and the rate of xylan accumulation in bamboo shoots. Yeast one-hybrid analysis suggested that PeMYB35 might be involved in xylan biosynthesis by regulating the expression of PeGT43-5 by binding to its 5' UTR/promoter. Our study provides a comprehensive understanding of PeGT43s in moso bamboo and lays a foundation for further functional analysis of PeGT43s for xylan biosynthesis during rapid growth.
木聚糖是最丰富的半纤维素之一，可交联纤维素和木质素，增加细胞壁的稳定性。许多编码糖基转移酶的基因在植物的木聚糖生物合成中起着至关重要的作用，如 GT43 家族。然而，竹子中的糖基转移酶知之甚少，尤其是作为木材替代品的木质竹。
从毛竹（Phyllostachys edulis）基因组中鉴定出 17 个 GT43 基因（PeGT43-1~PeGT43-17），它们属于三个亚家族，具有特定的基序。系统发育和共线性分析表明，PeGT43 可能经历了基因复制，因为在 12 对 PeGT43 之间以及 17 个 PeGT43 和 10 个 OsGT43 之间发现了共线性。在 PeGT43 启动子中发现了一组顺式作用元件，如激素、非生物胁迫反应和 MYB 结合元件。PeGT43 在 26 种组织中的表达不同，其中在芽中表达水平最高，尤其是在快速伸长区和节中。与 PeGT43 共表达的基因被注释为与多糖代谢和细胞壁生物合成有关。qRT-PCR 结果表明，共表达基因的表达模式相似，在快速生长过程中 4.0 m 芽中的表达水平显著增加，在 6.0 m 芽中达到峰值。此外，竹笋中木聚糖含量和结构多糖染色强度与 PeGT43 的表达呈强正相关。酵母单杂交实验表明，PeMYB35 可以通过结合 SMRE 顺式元件识别 PeGT43-5 的 5'UTR/启动子。
PeGT43 适应了快速细胞伸长和细胞壁积累过程中木聚糖生物合成的要求，这从 PeGT43 的表达谱和竹笋中木聚糖的积累速度得到了证明。酵母单杂交分析表明，PeMYB35 可能通过结合其 5'UTR/启动子来调节 PeGT43-5 的表达，从而参与木聚糖的生物合成。我们的研究为毛竹中的 PeGT43 提供了全面的了解，并为进一步研究 PeGT43 在快速生长过程中对木聚糖生物合成的功能分析奠定了基础。
