Stockhaus J., Schlue U., Koczor M., Chitty J. A., Taylor W. C., Westhoff P.
Institut fur Entwicklungsbiologie und Molekularbiologie der Pflanzen, Heinrich-Heine-Universitat Dusseldorf, Universitatsstrasse 1, 40225 Dusseldorf, Germany.
Plant Cell. 1997 Apr;9(4):479-489. doi: 10.1105/tpc.9.4.479.
The function of the C4 mechanism of photosynthesis depends on the strict compartmentation of the enzymes involved. Here, we investigate the regulatory mechanisms that ensure the mesophyll-specific expression of the C4 isoform of phosphoenolpyruvate carboxylase. We show that 2 kb of the 5[prime] flanking region of the Flaveria trinervia C4 PpcA1 gene is sufficient to direct mesophyll-specific expression of the [beta]-glucuronidase reporter gene in transgenic F. bidentis (C4) plants. In young leaves of seedlings, the activity of this promoter is dependent on the developmental stage of the mesophyll cells. It is induced in a basipetal fashion (leaf tip to base) during leaf development. The promoter region of the orthologous nonphotosynthetic Ppc gene of F. pringlei (C3) induces reporter gene expression mainly in the vascular tissue of leaves and stems as well as in mesophyll cells of transgenic F. bidentis plants. Our experiments demonstrate that during the evolution of the C4 Flaveria species, cis-acting elements of the C4 Ppc gene must have been altered to achieve mesophyll-specific expression.
光合作用的C4机制的功能取决于所涉及酶的严格区室化。在此，我们研究了确保磷酸烯醇式丙酮酸羧化酶C4同工型在叶肉细胞中特异性表达的调控机制。我们发现，三脉黄菊C4 PpcA1基因5′侧翼区域的2 kb片段足以指导β-葡萄糖醛酸酶报告基因在转基因二齿黄菊（C4）植物中进行叶肉特异性表达。在幼苗的幼叶中，该启动子的活性取决于叶肉细胞的发育阶段。在叶片发育过程中，它以向基方式（从叶尖到叶基部）被诱导。普氏黄菊（C3）直系同源非光合Ppc基因的启动子区域主要在转基因二齿黄菊植物叶片和茎的维管组织以及叶肉细胞中诱导报告基因表达。我们的实验表明，在C4黄菊属物种的进化过程中，C4 Ppc基因的顺式作用元件必定发生了改变以实现叶肉特异性表达。
