Agrocampus-Ouest, Institut de Recherche en Horticulture et Semences (INRA, Agrocampus-Ouest, Université d'Angers), SFR 149 QUASAV, F-49045 Angers, France.
J Plant Physiol. 2012 Sep 1;169(13):1271-80. doi: 10.1016/j.jplph.2012.04.014. Epub 2012 Jun 28.
Light is a critical determinant of plant shape by controlling branching patterns and bud burst in many species. To gain insight into how light induces bud burst, we investigated whether its inductive effect in rose was related to gibberellin (GA) biosynthesis. In axillary buds of beheaded plants subject to light, the expression of two GA biosynthesis genes (RoGA20ox and RoGA3ox) was promptly and strongly induced, while that of a GA-catabolism genes (RoGA2ox) was reduced. By contrast, lower expression levels of these two GA biosynthesis genes were found in darkness, and correlated with a total inhibition of bud burst. This effect was dependent on both light intensity and quality. In in vitro cultured buds, the inductive effect of light on the growth of preformed leaves and SAM organogenic activity was inhibited by ancymidol and paclobutrazol, two effectors of GA biosynthesis. This effect was concentration-dependent, and negated by GA(3). However, GA(3) alone could not rescue bud burst in the dark. GA biosynthesis was also required for the expression and activity of a vacuolar invertase, and therefore for light-induced sugar metabolism within buds. These findings are evidence that GA biosynthesis contributes to the light effect on bud burst and lay the foundations of a better understanding of its exact role in plant branching.
光是许多物种中控制分枝模式和芽萌发的植物形态的关键决定因素。为了深入了解光如何诱导芽萌发，我们研究了其在玫瑰中的诱导效应是否与赤霉素（GA）生物合成有关。在去头植物的腋芽中，光照会迅速且强烈地诱导两种 GA 生物合成基因（RoGA20ox 和 RoGA3ox）的表达，而 GA 分解代谢基因（RoGA2ox）的表达则减少。相比之下，在黑暗中，这两种 GA 生物合成基因的表达水平较低，与芽萌发的完全抑制有关。这种效应依赖于光照强度和质量。在体外培养的芽中，光照对预形成叶片生长和 SAM 器官发生活性的诱导效应被 ancymidol 和 paclobutrazol 抑制，这两种都是 GA 生物合成的效应物。这种效应呈浓度依赖性，可被 GA(3) 消除。然而，GA(3) 本身不能在黑暗中拯救芽萌发。GA 生物合成对于液泡转化酶的表达和活性也是必需的，因此对于光诱导芽内的糖代谢是必需的。这些发现证明了 GA 生物合成有助于光对芽萌发的影响，并为深入了解其在植物分枝中的确切作用奠定了基础。
