The TALE (Three Amino acid Loop Extension) transcription factor family has been shown to control meristem formation and organogenesis in plants. To understand the functional roles of the TALE family in woody perennials, each of the TALE members of Populus trichocarpa was overexpressed in Arabidopsis as a proxy. Among them, the overexpression of PtrTALE12 (i.e., 35S::PtrTALE12) resulted in a dramatic increase of axillary shoot development with early flowering. Interestingly, expression of WUSCHEL (WUS), a central regulator of both apical and axillary meristem formation, was significantly increased in the 35S::PtrTALE12 Arabidopsis plants. Conversely, WUS expression was downregulated in 35S::PtrTALE12-SRDX (short transcriptional repressor domain) plants. Further analysis found that PtrTALE12, expressed preferentially in meristem tissues, directly regulates WUS expression in transient activation assays using Arabidopsis leaf protoplast. Yeast two-hybrid assays showed that PtrTALE12 interacts with SHOOT MERISTEMLESS (STM); however, the interaction does not affect the WUS expression. In addition, expression of both CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) genes was suppressed accordingly for early flowering 35S::PtrTALE12 Arabidopsis. Indeed, transgenic poplars overexpressing PtrTALE12 as well as Arabidopsis plants overexpressing AtBLH11, a close homolog of PtrTALE12, phenocopied the 35S::PtrTALE12 Arabidopsis (i.e., increased axillary shoot development). Taken together, our results suggest that PtrTALE12 functions as a positive regulator of axillary shoot formation in both Arabidopsis and poplar.

中文翻译：

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胡杨转录因子PtrTALE12的过表达通过调节WUSCHEL表达来增加腋芽的发育。

TALE（三氨基酸环延伸）转录因子家族已被证明可控制植物的分生组织形成和器官发生。为了了解TALE家族在多年生木质植物中的功能作用，毛果杨的每个TALE成员都在拟南芥中过表达。其中，PtrTALE12（即35S :: PtrTALE12）的过度表达导致腋芽发育和早期开花的急剧增加。有趣的是，在35S :: PtrTALE12拟南芥植株中，WUSCHEL（WUS）（一种顶生和腋生分生组织形成的中央调节剂）的表达显着增加。相反，WUS在35S :: PtrTALE12-SRDX（短转录阻遏域）植物中，其表达下调。进一步的分析发现，优先使用分生组织表达的PtrTALE12在使用拟南芥叶片原生质体进行的瞬时激活测定中直接调节WUS表达。酵母两杂交试验表明，PtrTALE12与SHOOT MERISTEMLESS（STM）相互作用。但是，交互作用不会影响WUS表达。此外，早花35S :: PtrTALE12拟南芥相应地抑制了CIRCADIAN CLOCK ASSOCIATED1（CCA1）和晚期加长型油菜小体（LHY）基因的表达。实际上，过表达PtrTALE12的转基因杨树以及拟南芥过表达AtBLH11，一个接近的同源物PtrTALE12，表型模拟的35S :: PtrTALE12拟南芥（即增加副梢发展）。两者合计，我们的结果表明，PtrTALE12充当拟南芥和杨树中腋芽形成的正向调节剂。