. Incorporation of RNA precursor into the cell of Gyrodinium sp

Abstract

Gyrodinium sp., one kind of marine dinoflagellate which has been classified to belong to a new kingdom-Mesocaryote, was dealt with the existence of RNA and it mechanism of incorporation of 5-(superscript 3)H-uridine using electron microscopic autoradiography. Most of the silver grains distributed in the cytoplasm and some of them scattered in the chromosomes and nuclear envelope. In the cytoplasm, chloroplast is the most distinct organelle where numerous silver grains concentrated. The tritiated RNA precursor also labelled the mitochondrion, especially the stratified concentric mitochondrion. RNA synthesis is considered to take place at these regions. Ribosomes in three different sizes were found in the chloroplast, mitochondrion and cytoplasm matrix. Chloroplast and mitochondrion of Gyrodinium sp. are capable of protein synthesis and self-duplicating. Chloroplast, and. mitochondrional RNA coded from their own DNA as a template may be synthesized in. situ. But the amount of DNA in these organelles is much less than that of nuclear DNA, these organelles may not have so much genetic information to meet the requirement of protein synthesis for the whole cell. They may aggregate around the nucleus and receive genetic informations dispatched from the nuclear DNA at a certain cell stage.Gyrodinium sp.是海洋渦鞭毛藻(Dinoflagellate)之一種，屬於中核生物(Mesocaryote)，本報告在討論此生物RNA之存在部位及其合成機構，將Gyrodinium sp.在含有(上標 3)H-uridine之培養基下暴露一段時間，用電子顯微鏡自動放射圖法(Autoradiograph)研究之結果，發現大部份之銀粒子集中在細胞質，有一些分散在染色體及細胞核膜(Nuclear envelope)上。在細胞質內，葉綠體是銀粒子最多且最明顯之器官(Organelle)，銀粒子也存在於同心圓粒線體(Concentric mitochondrion),RNA合成被認爲在這些區域進行，三種不同大小之核糖體(Ribosome)散佈於葉綠體，粒線體以及細胞質基質(Cytoplasm matrix)上，葉綠體及粒線體能自行行蛋白質合成及自行分裂，它們可能以它本身含有之DNA做為鑄型(Template)在本身體內進行RNA合成，由於這些器官之DNA比細胞核之DNA量少的很多，當不可能有那麼多之遺傳情報(Genetic information)來滿足整個細胞之蛋白質要求，它們可能在某一定細胞週期，聚集到細胞核周圍而接受來自細胞核DNA之遺傳情報。