Devic M, Albert S, Delseny M
Laboratoire de Physiologie et Biologie Moleculaire Vegetales, University of Perpignan, France.
Plant J. 1996 Feb;9(2):205-15. doi: 10.1046/j.1365-313x.1996.09020205.x.
In order to assess the importance of morphogenesis on the induction of promoter markers for storage and Lea programmes, advantage was taken of the emb mutations producing embryos arrested at a wide range of developmental stages in Arabidopsis. These embryos are viable during their stage of developmental arrest and continue to divide further, but apparently without further differentiation into the main organs and tissues of the normal embryos. Eight independent emb mutants arrested in their development prior to the cotyledon stage were selected. These emb embryos lack the normal morphology of the wild-type embryos when the synthesis of storage and Lea proteins are normally initiated. The 2S1-uidA chimeric gene, representative of the maturation programme and the Em 1-uidA chimeric gene, representative of the desiccation programme were introduced by crosses into the emb background. In the eight emb lines, the expression of the GUS reporter gene directed by the 2S1 and Em 1 promoters was observed in the aborted seeds irrespective of their stage of developmental arrest. The time of induction of the expression of both promoters was the same in the arrested embryos as compared with the normal embryos within the same silique. Thus, the activation of these two promoters is triggered by the same signal and can occur in the absence of morphogenesis. However, in the absence of normal organ formation, the expression of the reporter gene under the control of the 2S1 and Em1 promoters was evident throughout the whole seed tissues. In normal seed development, the hormone abscisic acid (ABA) activates the promoters of the 2S1 and Em 1 genes. One of the important members of the signal transduction pathway of ABA is the ABI3 protein. It has been shown previously that this protein is a prerequisite for the induction of Em 1 by ABA in seeds. A good correlation with the expression of the ABI3 promoter and the 2S1 and Em 1 promoters was found in emb seeds tissues. This observation suggests that the promoters of the 2S1 and the Em 1 genes are expressed in the mutant seeds not at a basal level, but are probably induced by ABA, as in normal seed development.
为了评估形态发生对储存和Lea程序启动子标记诱导的重要性，利用了emb突变体，这些突变体产生的胚胎在拟南芥的广泛发育阶段停滞。这些胚胎在发育停滞阶段是有活力的，并继续进一步分裂，但显然没有进一步分化成正常胚胎的主要器官和组织。选择了八个在子叶阶段之前发育停滞的独立emb突变体。当储存蛋白和Lea蛋白的合成正常启动时，这些emb胚胎缺乏野生型胚胎的正常形态。代表成熟程序的2S1-uidA嵌合基因和代表干燥程序的Em1-uidA嵌合基因通过杂交被导入emb背景中。在这八个emb株系中，无论发育停滞阶段如何，在败育种子中都观察到由2S1和Em1启动子指导的GUS报告基因的表达。与同一角果中的正常胚胎相比，停滞胚胎中两个启动子表达的诱导时间是相同的。因此，这两个启动子的激活由相同信号触发，并且可以在没有形态发生的情况下发生。然而，在没有正常器官形成的情况下，在2S1和Em1启动子控制下的报告基因在整个种子组织中都有明显表达。在正常种子发育中，激素脱落酸（ABA）激活2S1和Em1基因的启动子。ABA信号转导途径的重要成员之一是ABI3蛋白。先前已经表明，这种蛋白是种子中ABA诱导Em1的先决条件。在emb种子组织中发现ABI3启动子与2S1和Em1启动子的表达有很好的相关性。这一观察结果表明，2S1和Em1基因的启动子在突变种子中不是以基础水平表达，而是可能像在正常种子发育中一样由ABA诱导。
