荞麦糊粉层和子叶中贮藏蛋白质积累过程的超微结构

THE ULTRASTRUCTURES OF STORAGE PROTEIN ACCUMULATION IN ALEURONE LAYER AND COTYLEDONS OF FAGOPYRUM ESCULENTUM

应用透射电镜技术对荞麦(Fagopyrum eaculentum)子叶和糊粉层细胞中贮藏蛋白质的积累过程进行了研究。荞麦开花后15天,胚乳最外层细胞的液泡中开始积累蛋白质。开花后25天,最外层胚乳细胞中积累较多的糊粉粒(直径1—2μm)形成糊粉层。开花后20天,子叶细胞中蛋白质开始在液泡和细胞质中积累,同时液泡通过膜的向内生长和缢裂两种方式形成体积较小的液泡。开花后25天,成熟的子叶细胞中含有丰富的蛋白质,贮藏蛋白质主要积累在液泡中形成体积较大的蛋白质贮藏液泡(PSVs,protein storage vacuoles,直径1—3μm)。在养麦子叶积累蛋白质的各个阶段,细胞质中都有一些来源于高尔基体、含蛋白质的电子不透明小泡(直径0.1—0.7μm)存在,观察到有些小泡正进入液泡,推断这种来自于高尔基体膜囊的小泡不仅有将蛋白质运输到液泡形成PSVs的作用,也可能是荞麦成熟子叶积累贮藏蛋白质的一种结构。

The ultrastructures of storage protein accumulation in cotyledons and aleurone layer in buckwheat (Fagopyrum esculentum Monch) were investigated by electron microscopy. (1) On 15 days after an-thesis (DAA), there are many dictyosomes and vacuoles accumulating protein in cytoplasm of the outer layer endosperm cells. These cells containing abundant aleurone grains (1 - 2 μm in diameter) from vacuoles accumulated storage protein form aleurone layer where division of aleurone grain is also observed on 25 DAA. (2) On 20 DAA, protein begins to accumulate in vacuoles of cotyledon cells. At the early stage of protein deposition, vacuoles are becoming smaller ones by ingrowth of tonoplast or by pinch - off. A multitude of ribosomes, many dictyosomes and electron- dense vesicles (0. 1 - 0. 7 μm in diameter) coated with membrane are observed in cytoplasm of cotyledon cells at every stage of protein accumulation. Originated from the separation of saccules containing protein at the fringe of dictyosome, these vesicles (0.1-0.2 μm in diameter) probably increase their volume by fusion each other. They play the leading role in transporting storage protein into vacuoles that become PSVs in cotyledon cells of buckwheat. On 25 DAA, there are many PSVs (1-3 μm in diameter) and some vesicles (0.1-0.7 μm) filled with protein in mature cotyledon cells. These vesicles may be also play a part in accumulating storage protein in mature buckwheat seed.