Of six TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF)-encoding genes in poplar, PtTDIF1 is predominantly expressed in adventitious roots (ARs), and the other five PtTDIFs are preferentially expressed in lateral roots (LRs). Upon auxin application, expression of all PtTDIFs declined in ARs but transiently increased in LRs. Both exogenous TDIF peptides and overexpression of PtTDIFs in poplar positively regulated the initiation and elongation of LRs, and overexpression of PtTDIFs also increased the number of ARs. As visualized by the auxin-responsive marker DR5:GUS, TDIF had differential impacts on the auxin signaling activity in ARs and LRs, which was corroborated by the free indole-3-acetic acid (IAA) measurements in them. Shoot tips of PtTDIF2- and PtTDIFL2-overexpressing (together as PtTDIFs^OE) trees revealed an enhanced IAA biosynthetic capacity, and removal of the aerial tissues dramatically diminished the root phenotypes of micro-propagated PtTDIFs^OE trees. Furthermore, PtTDIFs^OE poplars displayed an increased sensitivity for exogenous IAA, and N-1-naphthylphthalamic acid (NPA) completely blocked the TDIF-induced AR and LR formation. In PtTDIFs^OE roots, several auxin-related LR initiation markers such as GATA23, LBD16 and LBD29 were transcriptionally upregulated, further supporting that TDIF regulates LR organogenesis by strengthening the spatiotemporal auxin cues and that dynamic interplays between hormones govern root branching and developmental plasticity in tree species.

中文翻译：

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TDIF调节植物生长素的积累并调节植物生长素的敏感性，以增强杨树不定根和侧根的形成。

杨树中的六个气管元素分化抑制因子（TDIF）编码基因中，PtTDIF1主要在不定根（ARs）中表达，其他五个PtTDIFs优先在侧根（LRs）中表达。应用生长素后，AR中所有PtTDIFs的表达均下降，而LRs中的表达均短暂升高。杨树中的外源TDIF肽和PtTDIFs的过表达均积极调节LR的启动和延伸，PtTDIFs的过表达也增加了AR的数量。如生长素反应性标记DR5：GUS所示TDIF对ARs和LRs中的生长素信号传导活性有不同的影响，这通过其中的游离吲哚-3-乙酸（IAA）测量得到证实。的茎尖PtTDIF2-和PtTDIFL2-过表达（一起作为PtTDIFs ^OE）树显示的增强的生物合成IAA容量，并除去空中组织的显着减少微繁殖的根表型PtTDIFs ^OE树。此外，PtTDIFs ^OE杨对外源IAA的敏感性增强，N -1-萘基邻苯二甲酸（NPA）完全阻断了TDIF诱导的AR和LR的形成。在PtTDIFs ^OE中根部，一些与生长素相关的LR起始标记（如GATA23，LBD16和LBD29）在转录上被上调，进一步支持TDIF通过增强时空生长素提示来调节LR器官发生，并且激素之间的动态相互作用控制着树种的根分支和发育可塑性。