Mobile PEAR transcription factors integrate positional cues to prime cambial growth
Mobile PEAR transcription factors integrate positional cues to prime cambial growth
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DOI：
10.1038/s41586-018-0839-y
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发表时间：
2019-01-24
期刊：
影响因子：
64.8
通讯作者：
Helariutta, Yka
中科院分区：
文献类型：
--
作者：
Miyashima, Shunsuke;Roszak, Pawel;Helariutta, Yka
植物的顶端生长在种子萌发时开始，而径向生长仅在原形成层细胞的个体发育早期启动，随后被维管形成层激活(1)。虽然还不知道植物中径向生长是如何组织和调控的，但这个系统类似于在一些动物系统中观察到的发育能力，在动物系统中，预先存在的发育潜力模式是在很早就建立的(2，3)。在这里，我们表明，在拟南芥中，放射状生长的启动发生在根原形成层组织的早期原生韧皮部筛分细胞群周围。在这个区域，细胞分裂素信号转导促进一对可移动的转录因子-韧皮部早期DOF1(PEAR1)和韧皮部早期DOF2(PEAR2)-及其四个同源物(DOF6、TMO6、OBP2和HCA2)的表达，我们统称为梨蛋白质。梨蛋白质形成一个短距离的浓度梯度，在原生韧皮部筛分元件处达到顶峰，并激活促进径向生长的基因表达。梨树蛋白的表达和功能被HD-ZIP III蛋白、众所周知的极性转录因子(4)以及可移动的miR165和miR166 microRNAs所拮抗。HD-ZIP III蛋白是众所周知的极性转录因子(4)，其表达集中在生长素作用下径向不分裂的原形成层细胞的更内部区域。梨树蛋白质在局部促进其抑制基因HD-ZIP III的转录，从而建立一个负反馈循环，形成一个强大的边界，划定细胞分裂的区域。综上所述，我们的数据证实，在根的前形成层发育过程中，存在一个网络，其中连接PEAR和HD-ZIP III转录因子的模块整合了荷尔蒙结构域和miRNA梯度的空间信息，以提供相邻的分裂区域和更静止的细胞，这为进一步的径向生长奠定了基础。
Apical growth in plants initiates upon seed germination, whereas radial growth is primed only during early ontogenesis in procambium cells and activated later by the vascular cambium(1). Although it is not known how radial growth is organized and regulated in plants, this system resembles the developmental competence observed in some animal systems, in which pre-existing patterns of developmental potential are established early on(2,3). Here we show that in Arabidopsis the initiation of radial growth occurs around early protophloem-sieve-element cell files of the root procambial tissue. In this domain, cytokinin signalling promotes the expression of a pair of mobile transcription factors-PHLOEM EARLY DOF 1 (PEAR1) and PHLOEM EARLY DOF 2 (PEAR2)-and their four homologues (DOF6, TMO6, OBP2 and HCA2), which we collectively name PEAR proteins. The PEAR proteins form a short-range concentration gradient that peaks at protophloem sieve elements, and activates gene expression that promotes radial growth. The expression and function of PEAR proteins are antagonized by the HD-ZIP III proteins, well-known polarity transcription factors(4)-the expression of which is concentrated in the more-internal domain of radially non-dividing procambial cells by the function of auxin, and mobile miR165 and miR166 microRNAs. The PEAR proteins locally promote transcription of their inhibitory HD-ZIP III genes, and thereby establish a negative-feedback loop that forms a robust boundary that demarks the zone of cell division. Taken together, our data establish that during root procambial development there exists a network in which a module that links PEAR and HD-ZIP III transcription factors integrates spatial information of the hormonal domains and miRNA gradients to provide adjacent zones of dividing and more-quiescent cells, which forms a foundation for further radial growth.