Ohmiya Akemi, Hirashima Masumi, Yagi Masafumi, Tanase Koji, Yamamizo Chihiro
National Institute of Floricultural Science, National Agriculture and Food Research Organization, Fujimoto 2-1, Tsukuba, Ibaraki 305-8519, Japan.
PLoS One. 2014 Dec 3;9(12):e113738. doi: 10.1371/journal.pone.0113738. eCollection 2014.
Plants have an ability to prevent chlorophyll accumulation, which would mask the bright flower color, in their petals. In contrast, leaves contain substantial amounts of chlorophyll, as it is essential for photosynthesis. The mechanisms of organ-specific chlorophyll accumulation are unknown. To identify factors that determine the chlorophyll content in petals, we compared the expression of genes related to chlorophyll metabolism in different stages of non-green (red and white) petals (very low chlorophyll content), pale-green petals (low chlorophyll content), and leaves (high chlorophyll content) of carnation (Dianthus caryophyllus L.). The expression of many genes encoding chlorophyll biosynthesis enzymes, in particular Mg-chelatase, was lower in non-green petals than in leaves. Non-green petals also showed higher expression of genes involved in chlorophyll degradation, including STAY-GREEN gene and pheophytinase. These data suggest that the absence of chlorophylls in carnation petals may be caused by the low rate of chlorophyll biosynthesis and high rate of degradation. Similar results were obtained by the analysis of Arabidopsis microarray data. In carnation, most genes related to chlorophyll biosynthesis were expressed at similar levels in pale-green petals and leaves, whereas the expression of chlorophyll catabolic genes was higher in pale-green petals than in leaves. Therefore, we hypothesize that the difference in chlorophyll content between non-green and pale-green petals is due to different levels of chlorophyll biosynthesis. Our study provides a basis for future molecular and genetic studies on organ-specific chlorophyll accumulation.
植物具有防止叶绿素在花瓣中积累的能力，因为叶绿素积累会掩盖鲜艳的花色。相比之下，叶片含有大量叶绿素，因为叶绿素对光合作用至关重要。器官特异性叶绿素积累的机制尚不清楚。为了确定决定花瓣中叶绿素含量的因素，我们比较了香石竹（石竹）不同阶段非绿色（红色和白色）花瓣（叶绿素含量极低）、淡绿色花瓣（叶绿素含量低）和叶片（叶绿素含量高）中与叶绿素代谢相关基因的表达。许多编码叶绿素生物合成酶的基因，特别是镁螯合酶，在非绿色花瓣中的表达低于叶片。非绿色花瓣中参与叶绿素降解的基因，包括保持绿色基因和脱镁叶绿素酶，也表现出较高的表达。这些数据表明，香石竹花瓣中叶绿素的缺乏可能是由于叶绿素生物合成速率低和降解速率高所致。对拟南芥微阵列数据的分析也得到了类似的结果。在香石竹中，大多数与叶绿素生物合成相关的基因在淡绿色花瓣和叶片中的表达水平相似，而叶绿素分解代谢基因在淡绿色花瓣中的表达高于叶片。因此，我们推测非绿色花瓣和淡绿色花瓣之间叶绿素含量的差异是由于叶绿素生物合成水平不同所致。我们的研究为未来关于器官特异性叶绿素积累的分子和遗传研究提供了基础。
