Liu Qian-Yu, Guo Guang-Sheng, Qiu Zhen-Fei, Li Xiao-Dan, Zeng Bing-Shan, Fan Chun-Jie
Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou, 510520, People's Republic of China.
State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, 100091, People's Republic of China.
Protoplasma. 2018 Jul;255(4):1107-1119. doi: 10.1007/s00709-018-1218-0. Epub 2018 Feb 8.
Gibberellins (GAs) play a key role in plant growth and development including cell elongation, cell expansion, and xylem differentiation. Eucalyptus are the world's most widely planted hardwood trees providing fiber and energy. However, the roles of GAs in Eucalyptus remain unclear and their effects on xylem development remain to be determined. In this study, E. grandis plants were treated with 0.10 mg L GA and/or paclobutrazol (PAC, a GA inhibitor). The growth of shoot and root were recorded, transverse sections of roots and stems were stained using toluidine blue, and expression levels of genes related to hormone response and secondary cell wall biosynthesis were analyzed by quantitative real-time PCR. The results showed that GA dramatically promoted the length of shoot and root, but decreased the diameter of root and stem. Exogenous GA application also significantly promoted xylem development in both stem and root. Expression analysis revealed that exogenous GA application altered the transcript levels of genes related to the GA biosynthetic pathway and GA signaling, as well as genes related to auxin, cytokinin, and secondary cell wall. These findings suggest that GAs may interact with other hormones (such as auxin and cytokinin) to regulate the expression of secondary cell wall biosynthesis genes and trigger xylogenesis in Eucalyptus plants.
赤霉素（GAs）在植物生长发育过程中发挥着关键作用，包括细胞伸长、细胞扩张和木质部分化。桉树是世界上种植最广泛的硬木树，可提供纤维和能源。然而，赤霉素在桉树中的作用仍不明确，其对木质部发育的影响尚待确定。在本研究中，用0.10 mg L的赤霉素和/或多效唑（PAC，一种赤霉素抑制剂）处理巨桉植株。记录地上部和根部的生长情况，用甲苯胺蓝对根和茎的横切面进行染色，并通过实时定量PCR分析与激素反应和次生细胞壁生物合成相关基因的表达水平。结果表明，赤霉素显著促进了地上部和根部的长度，但减小了根和茎的直径。外源施加赤霉素也显著促进了茎和根中的木质部发育。表达分析表明，外源施加赤霉素改变了与赤霉素生物合成途径和赤霉素信号传导相关基因的转录水平，以及与生长素、细胞分裂素和次生细胞壁相关基因的转录水平。这些发现表明，赤霉素可能与其他激素（如生长素和细胞分裂素）相互作用，以调节次生细胞壁生物合成基因的表达并触发桉树植株中的木质部形成。
