【摘要】 利用DNA体外重组技术构建了蓝细菌Synechocystis sp.PCC 6803突变种ORF469~-,它的染色体DNA缺失ORF469片段,该突变种在加入5mmol/L葡萄糖的BG-11培养基中经遮光培养2周后叶绿素全部消失,细胞甲醇提取液光谱中665nm处叶绿素峰消失,629nm处出现原叶绿素酸酯峰,完整细胞光谱仅存在620nm的藻胆蛋白肩峰,细胞的类囊体膜消失,但藻胆体颗粒并未减少;细胞培养物重新暴露于光照下3h后,细胞甲醇提取液光谱中叶绿素峰开始高于原叶绿素酸酯峰,完整细胞光谱出现620nm藻胆蛋白峰和440nm叶绿素复合蛋白峰;光照8h后细胞内出现明显的类囊体膜;光照24h后,细胞甲醇提取液光谱的叶绿素峰恢复正常高度,原叶绿素酸酯峰消失,完整细胞光谱在680nm处出现叶绿素复合蛋白肩峰,细胞中也形成完整的类囊体膜层状结构;照光48h后,完整细胞光谱恢复与正常细胞光谱一致的峰形。说明叶绿素的生物合成控制类囊体膜的构建,继而使叶绿素复合蛋白在光系统中恢复生物学活性和功能。更多还原

【Abstract】 By DNA recombination technology in vitro, ORF469- mutant of cynobacterium Syne-chocystis sp. PCC 6803 was constructed, in which the ORF469 fragment relative to the light-independent protochlorophyllide (Pchlide) reduction was deleted. In BG-11 medium with 5 mmol/L glucose , the mutant was grown in darkness with a brief period (10 min) of illumination everyday (light-activated heterotrophic growth, LAHG) for 2 weeks to delete chlorophyll (Chl). The 665 nm Chi peak was replaced by the 629 nm Pchlide peak in the absorption spectra of the methanol extracts. The absorption spectra of the intact cells showed only shoulder peak at 620 nm (representing phyco-biliprotein). The thylakoid membrane disappeared, but the amount of phycobilisome did not decrease . When the mutant was transferred from LAHG condition to continuous light illumination for 3 h, the absorbance at 665 run became higher than that at 629 nm and two peaks at 620 nm and 440 run, representing phycobiliprotein and Chl-protein complex respectively, appeared in the absorption spectra of the intact cells. After exposure to the light for 8 h, the thylakoid membrane was visible in the cells. And for 24 h, a shoulder peak was present at 680 nm in the absorption spectra of the intact cells. Meanwhile the absorption spectra of the methanol extracts had no difference from that of cells grown in the light. After 48 h, the shape of the absorption spectra of the intact cells became the same as that of cells grown in the light. The layers of thylakoid membranes were as clear as those of the cells grown in the light. The results indicated that the biosynthesis of chlorophyll regulates the reconstruction of thylakoid membrane rendering the Chl protein complex to play its functional role in photosystems.更多还原