磷缺失引起小麦叶片中脂含量的变化与脂的合成和磷脂酰甘油的降解有关(英文)

对生长在不同磷营养水平条件下小麦(Triticum aestivum var.Zhongyou 9507)叶片中光合膜脂含量变化的原因进行了研究。通过对生长在不同磷营养水平条件下9 d龄和16 d龄小麦叶片中光合膜脂含量的分析,发现在磷缺失培养条件下,小麦光合膜脂的相对含量发生了很大变化,这种变化与小麦叶龄密切相关。在16 d龄小麦植株中,第一片叶为老叶,第二片叶为较老叶,而第三片叶为新叶,PG和MGDG在叶片中的相对含量从新叶到老叶逐渐下降,而DGDG和SQDG含量逐渐上升;在磷缺失条件下,16 d龄小麦第一叶片中PG的含量(2.5％)远远低于其在9 d龄第一叶片中的含量(5.5％)。以上结果说明,磷缺失引起小麦叶片中脂含量的变化不仅与脂合成有关,而且与PG的降解有关;新生叶片中PG含量减少的主要原因是由于磷供应不足,从而影响了PG的合成;而PG的降解则是老叶中PG含量下降的主要原因。     

Characterization of the Main Light-Harvesting Chlorophyll a／b-Protein Complex of Green Alga, Bryopsis corticulans

The main light-harvesting chlorophyll a/b -protein complex (LHC Ⅱ) has been isolated directly from thylakoid membranes of shiphonous 8Teen alga, Bryopsis corticulans Setch. by using two consecutive runs of anion exchange and gel-filtration chromatography. Monomeric and trimeric subcomplexes of LHC Ⅱ were obtained by using sucrose gradient ultracentrifugation. Pigment analysis by reversed-phase high performance liquid chromatography showed that chlorophyll a (Chl a), chlorophyll b (Chl b), neoxanthin, violaxanthin and siphonaxanthin were involved in LHC Ⅱ from B. corticulans. The properties of electronictransition of monomeric LHC Ⅱ showed similarities to those of trimeric LHC Ⅱ. Circular dichroism spectroscopy showed that strong intramolecular interaction of excitonic dipoles between Chl a and between Chl b exist in one LHC Ⅱ apoprotein, while the intermolecular interaction of these dipoles can be intensified in the trimeric structure. The monomer has high efficient energy transfer from Chl b and siphonaxanthin to Chl a similarly to that of the trimer. Our results suggest that in B. corticulans, LHC Ⅱ monomer has high ordered pigment organization that play effective physiological function as the trimer, and thus it might be also a functional organization existing in thylakoid membrane of B.corticulans.     

Isolation and Characterization of the Cytoplasmic Membrane from the Terrestrial Cyanobacterium -Nostoc flagelliforme

Cytoplasmic membrane of Nostoc flagelliforme Born. et Flah. was isolated for the first time with a new method, the unique feature of which is the combined use of French pressure cell and digitonin to disrupt cells. After passed twice through French pressure cell (at 80 MPa), cells in sample (20 mg of dry weight/mL) were disrupted effectively by digitonin (3 mg/mL), and then the cytoplasmic membrane was isolated by density gradient centrifugation. The membrane contained carotenoids with absorption peaks at 458, 487 and 524 nm and a precursor of chlorophyll a with a minor peak at 673 nm. The fluorescence emission peaks of the membrane were emitted from the precursor of chlorophyll a. More than 30 polypeptides were detected in the membrane, in which the most obvious corresponded to the polypeptides with molecular mass of 80,28,19 and 17 kD. The membrane contained four types of glycerolipids: MGDG(62.4%), DGDG (18.9%), SQDG (16.7%) and PG (2.0%). 16:0, 16:1 [9], 18:0, 18:1 [9], 18:2 [9, 12] and 18:3 [9,12,15] fatty acids were determined in the membrane, in which 16:1 and 18:3 fatty acids were the main components, representing 32.3% and 34.4% of the total fatty acids respectively. High proportion of 18:3 fatty acid in the cytoplasmic membrane may be an important factor of N. flagelliforme in its remarkable drought-tolerant ability.