莲子光下萌发过程中光合膜超分子结构与27kD多肽变化

CHANGES OF FREEZE-FRACTURE ULTRASTRUCTURE AND 27 kD POLYPEPTIDE OF PHOTOSYNTHETIC MEMBRANES DURING THE GERMINATION OF LOTUS SEEDS UNDER LIGHT

冰冻撕裂电镜观察及膜多肽组分的研究结果表明,随着莲子在光下萌发时间的延长,莲(Nelumbonucifera Gaertn.)胚芽叶的叶绿体光合膜的超分子结构发育与膜多肽组分中的27kD多肽含量变化具有明显的相关性:1.萌发2d后,胚芽叶的叶绿体巨基位变成解垛叠状态,其光合膜的超分子结构只呈现解垛叠类囊体区外质膜撕裂面(EF)和解垛叠类囊体的原生质膜撕裂面(PF)两个面;膜组分中主要是30kD多肽,而27kD多肽含量甚微。2.萌发4d后,光合膜从解垛叠开始转变成小基粒垛,垛叠区类囊体外质膜撕裂面(EFs)和垛叠类囊体的原生质膜撕裂面(PFs)开始发育;27kD多肽含量开始增加,30kD多肽含量开始减少。3.萌发6～8d后,光合膜明显分化出非垛叠膜区,非垛叠类囊体的外质膜撕裂面(EFu)和非垛叠类囊体的原生质膜撕裂面(PFu)开始呈现,EFs和PFs功能蛋白颗粒逐渐增多;27kD多肽逐渐增加,30kD多肽逐渐减少。4.萌发10～12d后,光合膜垛叠和非垛叠膜区分化完善,排列有序,EFs、PFs、EFu和PFu面功能蛋白颗粒的密度、大小、分布等超分子构象发育正常;27kD多肽更加增多,30kD多肽几乎消失。表明其超分子结构的发育动态既与其超微结构变化相一致,又与27kD多肽含量变化相吻合,却与一般高等植物的叶绿体发育相反。

Investigation of freeze-fracture electron microscopy and analysis of polypeptide components of photosynthetic membranes from lotus (Nelumbo mtcifera Gaertn.) showed that the ultra-structural development of chloroplast photosynthetic membranes in the plumule were in concert with the changes of 27 kD polypeptide (LHC Ⅱ) during the germination of lotus seeds under light. 1) Two days after germination, the thylakoid membranes of giant grana became destacked. Only endo-plasmic fracture face of destacked thylakoid region (EF) and protoplasmic fracture face of destacked thylokoids (PF) could be observed with freeze-fracture electron microscopy. The majority was 30 kD polypeptide, but 27 kD was scarce. 2) Four days after germination, photosynthetic membranes changed from destacked type to small grana. At the same time, the particle density of the endoplas-mic fracture face in the stacked thylakoid region (EFs) and protoplasmic fracture face in the stacked thylakoid region (PFs) began to develop and 27 kD increased while 30 kD decreased. 3) 6 to 8 days after germination, the unstacked membrane region was developed, the particle density of the endoplasmic fracture face in the unstacked region (EFu) and protoplasmic fracture face in the unstacked region (PFu) could be seen. The particles on EFs and PFs gradually appeared. In the meantime, 27 kD kept on increasing while 30 kD decreasing. 4) 10 to 12 days after germination, fully developed stacked and unstacked photosynthetic membranes arranged orderly in the chloroplast. The density, size and distribution of particles on EFs, PFs, EFu and PFu developed normally. There were more and more 27 kD polypeptide, as 30 kD almost disappeared. It was significant that the ongoing changes of supramolecular architecture concured with the changes of the ultrastructure and the quantitative variations of 27 kD polypeptide. Thus not only proved that LHC II is the main internal factor which induce the membrane stacking, but also gave the evidence which indicated that sacred lotus possess an unique position in phylogeny of Angiospermae.