海洋管藻目绿藻——刺松藻和假根羽藻PSI荧光特异性的研究

CHARACTERIZATION OF PSI FLUORESCENCE IN SIPHONOUS MARINE GREEN ALGAE, CODIUM FRAGILE AND BRYOPSIS CORTICULANS

采用分离、原位扫描和光谱分析方法 ,将管藻目绿藻刺松藻和假根羽藻的叶绿体、类囊体膜、PSI复合物及其亚复合物的结构及光谱性质与软丝藻和菠菜做了比较。结果表明 ,管藻目绿藻缺少作为高等植物PSI表征的 730nm长波荧光 ,这一特异现象主要与LHCI结构的差异有关。采用PAGE法分离出的 4种PSI复合物的荧光主发射峰分别在 698、690、685和677nm ,在 71 0— 71 5nm处有一个随分子量减小而逐渐明显的肩峰。不同去污剂处理只影响PSI复合物荧光峰的高低 ,而不影响其峰位。PAGE再分离得到的假根羽藻LHCI由 2 4—2 7.5kDa的 4种多肽构成 ,Chl -a Chl-b =1 .2 ,77K荧光发射峰在 682nm ;CCI只含有 67和5 6kDa多肽 ,是叶绿体 71 5nm荧光的发射部位。当有LHCI存在时 。

Structural and spectral characters of chloroplas t, thylakoi ds, PSI chlorophyll-protein complexes and their sub-complexes LHCI and CCI iso lated from two species of siphonous green algae, Codium fragile and Bryop sis corticulans, were studied and compared with those of green alga Ulothrix flacca and spinach. Affection on the long wavelength of PSI complexes of diff erent types of detergents was also investigated. The results showed that all of t he three green algae lacked the 730nm characteristic emission band which is rega rded as a symbol of PSI in higher plants. The main fluorescence emissions in chl oroplasts and thylakoids isolated from C. fragile and B. corticulans wer e all near 685nm and 695nm, a shoulder around 710-715nm with an unknown origin was also identified. The largest PSI complex resolved from spinach thylakoids by PAGE has a long wavelength emission around 730nm, U. flacca at 715nm. The e mission bands of three CPIa complexes from C. fragile and B. corticulans were associated with single wide peaks, with wavelengths of shorter than 700nm , at 698, 690, 685nm, respectively. CPI of spinach had an emission maximum at 72 0nm and U. flacca at 715nm, C. fragile and B. corticulans at 677nm; the peak between 710-715nm was half-hidden. The fluorescent peaks of PSI compl exes resolved by three different detergents, SDS, DMG and DOC, differed in their heights other than their wavelengths. It suggests that the separating procedure and the detergents have no relationship with the differences of PSI fluorescence emission positions among spinach, U. flacca and two species of siphonous gr een algae. By further fraction of PSI complexes under PAGE, the light-harvestin g complex LHCI and core complex CCI of B. corticulans were obtained. LHCI co nsisted of four peptides of 27.5, 26.2, 26 and 24kDa, and had a fluorescence emi ssion around 682-683nm other than 730nm in higher plants at 77K. It attached mo re tightly with CCI than those of U. flacca or spinach. CCI depleting of LHC I contained only 67 and 56 kDa peptides, and meanwhile, its fluorescent band aro und 710-715nm became remarkable. The un-located fluorescence emission in two s pecies siphonous chloroplasts was originated from CCI. The presence of LHCI made the CCI fluorescence band half-hidden. Further, the differences of LHCI peptid es and fluorescence characteristics were the main structural reason that caused the difference of fluorescence in siphonous green algae.