Université d'Angers, UMR1345 Institut de Recherche en Horticulture et Semences, SFR 4207 QUASAV, PRES L'UNAM, F-49045, Angers, France; INRA, UMR1345 Institut de Recherche en Horticulture et Semences, F-49071, Beaucouzé, France.
Plant Cell Environ. 2014 Mar;37(3):742-57. doi: 10.1111/pce.12191. Epub 2013 Sep 23.
Light and temperature are two environmental factors that deeply affect bud outgrowth. However, little is known about their impact on the bud burst gradient along a stem and their interactions with the molecular mechanisms of bud burst control. We investigated this question in two acrotonic rose cultivars. We demonstrated that the darkening of distal buds or exposure to cold (5 °C) prior to transfer to mild temperatures (20 °C) both repress acrotony, allowing the burst of quiescent medial and proximal buds. We sequenced the strigolactone pathway MAX-homologous genes in rose and studied their expression in buds and internodes along the stem. Only expressions of RwMAX1, RwMAX2 and RwMAX4 were detected. Darkening of the distal part of the shoot triggered a strong increase of RwMAX2 expression in darkened buds and bark-phloem samples, whereas it suppressed the acropetal gradient of the expression of RwMAX1 observed in stems fully exposed to light. Cold treatment induced an acropetal gradient of expression of RwMAX1 in internodes and of RwMAX2 in buds along the stem. Our results suggest that the bud burst gradient along the stem cannot be explained by a gradient of expression of RwMAX genes but rather by their local level of expression at each individual position.
光是两个环境因素，深刻地影响芽生长。然而，它们对芽裂梯度的影响及其与芽裂控制的分子机制之间的相互作用知之甚少。我们在两个桃金娘品种中研究了这个问题。我们证明，在转移到温和温度（20°C）之前，远端芽的变暗或暴露于低温（5°C）都会抑制桃金娘酸，从而允许静止的中芽和近端芽破裂。我们对玫瑰中的独脚金内酯途径 MAX 同源基因进行了测序，并研究了它们在芽和节间沿茎的表达。仅检测到 RwMAX1、RwMAX2 和 RwMAX4 的表达。在光照下，茎的远端部分变暗会导致 RwMAX2 在变暗的芽和树皮韧皮部样本中的表达强烈增加，而抑制了 RwMAX1 在茎中观察到的向顶梯度表达。低温处理诱导 RwMAX1 在节间和 RwMAX2 在芽中的向顶梯度表达。我们的结果表明，芽裂梯度沿茎不能用 RwMAX 基因的表达梯度来解释，而是由它们在每个单独位置的局部表达水平来解释。
