Plant Biotechnology Research Center, SJTU-Cornell Institute of Sustainable Agriculture and Biotechnology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
Plant Biotechnology Research Center, SJTU-Cornell Institute of Sustainable Agriculture and Biotechnology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
Plant Sci. 2019 Sep;286:7-16. doi: 10.1016/j.plantsci.2019.05.020. Epub 2019 Jun 1.
Cotton fibers are developed epidermal cells of the seed coat and contain large amounts of cellulose and minor lignin-like components. Lignin in the cell walls of cotton fibers effectively provides mechanical strength and is also presumed to restrict fiber elongation and secondary cell wall synthesis. To analyze the effect of lignin and lignin-like phenolics on fiber quality and the transcriptional regulation of lignin synthesis in cotton fibers, we characterized the function of a bHLH transcription factor, GhbHLH18, during fiber elongation stage. GhbHLH18 knock-down plants have longer and stronger fibers, and accumulate less lignin-like phenolics in mature cotton fibers than control plants. By mining public transcriptomic data for developing fibers, we discovered that GhbHLH18 is coexpressed with most lignin synthesis pathway genes. Furthermore, we showed that GhbHLH18 strongly binds to the E-box in the promoter region of GhPER8 and activates its expression. Transient over expression of GhPER8 protein in tobacco leaves significantly decreased the content of coniferyl alcohol and sinapic alcohol-the substrate respectively for G-lignin and S-lignin biosynthesis. These results suggest that GhbHLH18 is negatively associated with fiber quality by activating peroxidase-mediated lignin metabolism, thus the paper represents an alternative strategy to improve fiber quality.
棉花纤维是种皮的表皮细胞发育而来的，含有大量的纤维素和少量木质素样成分。细胞壁中的木质素有效地提供了机械强度，同时也被认为限制了纤维的伸长和次生细胞壁的合成。为了分析木质素和木质素样酚类物质对纤维质量的影响以及木质素合成的转录调控，我们在纤维伸长阶段对一个 bHLH 转录因子 GhbHLH18 的功能进行了表征。GhbHLH18 敲低植物的纤维较长且强度较大，成熟棉花纤维中的木质素样酚类物质积累较少。通过挖掘公开的纤维发育转录组数据，我们发现 GhbHLH18 与大多数木质素合成途径基因共表达。此外，我们还表明 GhbHLH18 可以强烈结合 GhPER8 启动子区域的 E-box 并激活其表达。在烟草叶片中瞬时过表达 GhPER8 蛋白显著降低了松柏醇和芥子醇的含量，分别是 G-木质素和 S-木质素生物合成的底物。这些结果表明，GhbHLH18 通过激活过氧化物酶介导的木质素代谢与纤维质量呈负相关，因此该论文代表了一种改善纤维质量的替代策略。
