High levels of auxin signalling define the stem-cell organizer of the vascular cambium
High levels of auxin signalling define the stem-cell organizer of the vascular cambium
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DOI：
10.1038/s41586-018-0837-0
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发表时间：
2019-01-24
期刊：
影响因子：
64.8
通讯作者：
Mahonen, Ari Pekka
中科院分区：
文献类型：
--
作者：
Smetana, Ondrej;Makila, Riikka;Mahonen, Ari Pekka
木材是木质部组织的一种，起源于维管形成层的细胞增殖。木质部产生于形成层内部，韧皮部产生于形成层外部（1）。植物的形态建成通常由组织细胞协调，组织细胞指导邻近的干细胞进行程序性细胞分裂和分化。维管形成层干细胞的位置以及组织者概念是否适用于形成层目前尚不清楚（2）。在这里，使用谱系追踪和分子遗传学研究在拟南芥的根，我们表明，细胞与木质部的身份直接相邻的维管形成层细胞分裂和干细胞的功能。因此，这些木质部同一性细胞构成组织者。植物激素生长素的局部最大值和随后的III类HOMEODOMAIN-LEUCINE ZIPPER（HD-ZIP III）转录因子的表达促进了木质部的特性和组织细胞的细胞静止。此外，组织者以非细胞自主的方式维持韧皮部的身份。与组织细胞的这种双重功能一致，木质部和韧皮部起源于每个放射状细胞列中的单个双面干细胞，这证实了单列维管形成层的经典理论（3）。显示高水平异位激活生长素信号的克隆分化为木质部导管;这些克隆诱导细胞分裂和形成层和韧皮部标记在相邻细胞中的表达，这表明局部生长素信号最大值足以指定干细胞组织者。虽然维管形成层在植物分生组织中具有独特的功能，但该组织的干细胞组织者与根和茎分生组织者具有共同的特征。
Wood, a type of xylem tissue, originates from cell proliferation of the vascular cambium. Xylem is produced inside, and phloem outside, of the cambium(1). Morphogenesis in plants is typically coordinated by organizer cells that direct the adjacent stem cells to undergo programmed cell division and differentiation. The location of the vascular cambium stem cells and whether the organizer concept applies to the cambium are currently unknown(2). Here, using lineage-tracing and molecular genetic studies in the roots of Arabidopsis thaliana, we show that cells with a xylem identity direct adjacent vascular cambial cells to divide and function as stem cells. Thus, these xylem-identity cells constitute an organizer. A local maximum of the phytohormone auxin, and consequent expression of CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors, promotes xylem identity and cellular quiescence of the organizer cells. Additionally, the organizer maintains phloem identity in a non-cell-autonomous fashion. Consistent with this dual function of the organizer cells, xylem and phloem originate from a single, bifacial stem cell in each radial cell file, which confirms the classical theory of a uniseriate vascular cambium(3). Clones that display high levels of ectopically activated auxin signalling differentiate as xylem vessels; these clones induce cell divisions and the expression of cambial and phloem markers in the adjacent cells, which suggests that a local auxin-signalling maximum is sufficient to specify a stem-cell organizer. Although vascular cambium has a unique function among plant meristems, the stem-cell organizer of this tissue shares features with the organizers of root and shoot meristems.