阿拉伯芥ch5突變種的葉綠餅層疊現象

Abstract

阿拉伯芥ch5突變種是一種受EMS誘變產生的chlorina突變種，本實驗室先前曾觀察出其突變種的類囊體膜層疊效果較正常種鬆散。從各種光合色素的分析可顯示出，ch5突變種的色素含量只有正常種的一半，且葉綠素a/b也較高。若受不同光強度處理時，其色素的變化形式在兩者卻是相似的。SDS-PAGE電泳圖譜發現，構成LHC的全部蛋白質都比正常種少，以25、26和27 kD最為明顯，另外，還多出22、13、12 kD三種蛋白質，以及19 kD蛋白質的消失，至於兩大光系統反應中心並無明顯變化。由色素蛋白質複合體電泳圖譜，經吸收及螢光光譜鑑定這些色素蛋白質複合體有很大的不同，推測這些變異的蛋白質似乎與LHC有關。另外，在色素蛋白質複合體進行電泳時亦發現，ch5突變種的色素蛋白質複合體有擴散現象；表面張力測定也有很大的差異。以digitonin處理時，ch5突變種的類囊體膜會比正常種更易在較低十倍的濃度就破壞膜系而溶出葉綠素。膜系的脂肪分析，顯示ch5突變種的galactolipids含量下降而sterol glycoside則上升4-5倍以上，使得我們推測ch5突變種的類囊體膜系有不正常的結構，其表面離子強度弱與流動性慢。須進一步探討脂肪和蛋白質的變異現象，以瞭解為何會影響類囊體膜的層疊效果。

Ch5 mutant that is induced by EMS, is a chlorina mutant of Arabidopsis thaliana. The grana stacking of this mutant was found loose than that of wild type in previous observation. Photosynthetic pigments' analysis showed ch5 mutant contained only half of the pigment of wild type and a higher Chl a/b ratio. In the treatments of three light intensities, the change patterns of all pigments are similar in ch5 mutant and wild type. The total proteins of the light-harvesting complexes in ch5 mutant are less than those in wild type, especially, 25, 26 and 27 kD proteins are most obviously; increases in 22, 13 and 12 kD proteins and loses 19 kD protein. However, the reactive centers of two photosystems are not obviously changed. It is showed that the pigment-protein complexes in ch5 mutant are different from the analysis of the absorption and fluorescence spectrums. Therefore, it are closely related between the proteins and the light-harvesting complexes. Pigment-proteins complexes of ch5 mutant are diffused in the electrophoresis patterns is found, the surface tension of the thylakoid membranes of ch5 mutant are more different than that of wild type. In the digitonin treatment, chlorophyll is solubilized more easily from the thylakoid membranes of ch5 mutant than that of wild type. It demonstrates that the galactolipids of ch5 mutant are reduced and the sterol glycoside are increased in camparing with wild type. Therefore, the thylakoid membranes of ch5 mutant is anormal structures, the ion strength of thylakoid membrane is weak and the fluidity is slow were suggested.