Cytokinin signaling localized in phloem noncell-autonomously regulates cambial activity during secondary growth of Populus stems
Cytokinin signaling localized in phloem noncell-autonomously regulates cambial activity during secondary growth of Populus stems
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位于韧皮部的细胞分裂素信号非细胞自主调节杨茎二次生长过程中的形成层活性
DOI：
10.1111/nph.17255
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发表时间：
2021-03-08
期刊：
影响因子：
9.4
通讯作者：
Luo, Keming
中科院分区：
文献类型：
--
作者：
Fu, Xiaokang;Su, Huili;Luo, Keming
通过调节细胞分裂素的含量，揭示了细胞分裂素对次生维管发育的调节作用。然而，目前尚不清楚发育中的次生韧皮部中富集的细胞分裂素如何调节杨树形成层活性。在这里，我们通过免疫组织化学成像观察了细胞分裂素在白杨茎次生韧皮部中的梯度分布，并确定了位于韧皮部的细胞分裂素信号传导在木材形成过程中的作用。我们产生了含有细胞分裂素氧化酶/脱氢酶（CKX）2的转基因白杨，编码细胞分裂素降解酶的基因，由韧皮部特异性CLE 41 b启动子驱动，表明细胞分裂素梯度模式的破坏限制了形成层的活性。RNA干扰为基础的敲低组氨酸激酶（HK）基因编码的细胞分裂素受体特异性次生韧皮部显着损害形成层细胞的分裂活动，而韧皮部特异性表达的B型反应调节因子（RR）转录因子刺激形成层增殖，提供证据的非细胞自主调节的局部细胞分裂素信号传导的形成层活动。此外，形成层特异性的HKs敲除也导致形成层活动受限，而细胞分裂素积累的减少则加剧了这种缺陷。我们的研究结果表明，次生韧皮部局部的细胞分裂素信号非细胞自主地调节形成层的活动，并与其在形成层中的局部信号相互协调。
The regulation of cytokinin on secondary vascular development has been uncovered by modulating cytokinin content. However, it remains unclear how cytokinin enriched in developing secondary phloem regulates cambium activity in poplar.Here, we visualized the gradient distribution of cytokinin with a peak in the secondary phloem of poplar stem via immunohistochemical imaging, and determined the role of phloem-located cytokinin signaling during wood formation.We generated transgenic poplar harboring cytokinin oxidase/dehydrogenase (CKX)2, a gene encoding a cytokinin degrading enzyme, driven by the phloem-specific CLE41b promoter, indicating that the disruption of the cytokinin gradient pattern restricts the cambial activity. The RNA interference-based knockdown of the histidine kinase (HK) genes encoding cytokinin receptors specifically in secondary phloem significantly compromised the division activity of cambial cells, whereas the phloem-specific expression of a type-B response regulator (RR) transcription factor stimulated cambial proliferation, providing evidence for the noncell-autonomous regulation of local cytokinin signaling on the cambial activity. Moreover, the cambium-specific knockdown of HKs also led to restricted cambial activity, and the defects were aggravated by the reduced cytokinin accumulation.Our results showed that local cytokinin signaling in secondary phloem regulates cambial activity noncell-autonomously, and coordinately with its local signaling in cambium.