Differential regulation of auxin and cytokinin during the secondary vascular tissue regeneration in Populus trees
Differential regulation of auxin and cytokinin during the secondary vascular tissue regeneration in Populus trees
复制标题
杨树次生维管组织再生过程中生长素和细胞分裂素的差异调节
DOI：
10.1111/nph.16019
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发表时间：
2019-08-02
期刊：
影响因子：
9.4
通讯作者：
He, Xin-Qiang
中科院分区：
文献类型：
--
作者：
Chen, Jia-Jia;Wang, Ling-Yan;He, Xin-Qiang
植物创伤后的组织再生是植物发育可塑性的重要表现。以往的研究描述了树木大规模树皮环剥后次生维管组织（SVT）再生的形态学和分子变化。然而，植物激素如何调节SVT再生仍然是未知的。本研究以杂交白杨（Populus tremula x Populus tremuloides）无性系T89为试材，建立了一个新的离体SVT再生体系。通过外源激素的施用和不同转基因植株的利用，研究了植物激素对SVT再生的影响。血管组织特异性标志物和激素反应因子也在SVT再生过程中进行了检查。利用这个离体再生系统，我们证明了生长素和细胞分裂素差异调节韧皮部和形成层再生。而生长素是足以诱导再生韧皮部之前，连续形成层恢复，细胞分裂素只促进新的韧皮部，而不是形成层的形成。细胞分裂素对韧皮部再生的积极作用在细胞分裂素过量表达的树中得到进一步证实。DR5报告基因转基因株系的分析进一步表明，细胞分裂素阻断了形成层形成所需的生长素梯度的重建。对生长素和细胞分裂素信号基因的研究表明，这两种激素相互作用调节SVT再生。总之，体外SVT再生系统允许我们利用各种分子和遗传工具来研究SVT再生。我们的研究结果证实，生长素和细胞分裂素的互补结构域所需的韧皮部和形成层重建。
Tissue regeneration upon wounding in plants highlights the developmental plasticity of plants. Previous studies have described the morphological and molecular changes of secondary vascular tissue (SVT) regeneration after large-scale bark girdling in trees. However, how phytohormones regulate SVT regeneration is still unknown. Here, we established a novel in vitro SVT regeneration system in the hybrid aspen (Populus tremula x Populus tremuloides) clone T89 to bypass the limitation of using field-grown trees. The effects of phytohormones on SVT regeneration were investigated by applying exogenous hormones and utilizing various transgenic trees. Vascular tissue-specific markers and hormonal response factors were also examined during SVT regeneration. Using this in vitro regeneration system, we demonstrated that auxin and cytokinin differentially regulate phloem and cambium regeneration. Whereas auxin is sufficient to induce regeneration of phloem prior to continuous cambium restoration, cytokinin only promotes the formation of new phloem, not cambium. The positive role of cytokinin on phloem regeneration was further confirmed in cytokinin overexpression trees. Analysis of a DR5 reporter transgenic line further suggested that cytokinin blocks the re-establishment of auxin gradients, which is required for the cambium formation. Investigation on the auxin and cytokinin signalling genes indicated these two hormones interact to regulate SVT regeneration. Taken together, the in vitro SVT regeneration system allows us to make use of various molecular and genetic tools to investigate SVT regeneration. Our results confirmed that complementary auxin and cytokinin domains are required for phloem and cambium reconstruction.