Mauriat Mélanie, Petterle Anna, Bellini Catherine, Moritz Thomas
Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 87, Umeå, Sweden; Institut National de la Recherche Agronomique, UMR 1202 BIOGECO, 69 route d'Arcachon, F-33612, Cestas Cedex, France.
Plant J. 2014 May;78(3):372-84. doi: 10.1111/tpj.12478. Epub 2014 Apr 2.
Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula × tremuloïdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis.
了解不定根形成过程对于增进对植物生理学的基本理解以及多种植物的繁殖都很重要。过表达关键赤霉素（GA）生物合成基因（AtGA20ox1）的杂种山杨（Populus tremula × tremuloïdes）植株生长迅速，但生根效率低下，这限制了它们的克隆繁殖。因此，我们研究了杨树和模式植物拟南芥不定根形成的分子基础。树木插条中不定根（ARs）的产生始于茎基部区域，涉及多种内源性和外源性因素的相互作用。几种激素在这一过程中的作用已得到表征，但GA的影响尚未得到充分研究。在这里，我们表明GA处理对野生型杂种山杨插条产生的ARs数量有负面影响。此外，过表达AtGA20ox1、PttGID1.1或PttGID1.3基因（带有35S启动子）的杂种山杨植株和完整拟南芥幼苗产生的ARs都很少，尽管ARs是从杂种山杨的茎基部区域和拟南芥的下胚轴发育而来的。在拟南芥中，已知生长素和独脚金内酯会影响AR形成。我们的数据表明，GA处理对不定根形成的抑制作用不是由生长素信号通路、独脚金内酯生物合成和信号通路的扰动介导的。相反，GA似乎是通过干扰极性生长素运输来起作用的，特别是在杂种山杨中干扰生长素外流，在拟南芥中干扰外流和内流。
