Studies of photosystem complexes and chlorophyll synthesis in chlorophyll-deficient rice mutant W1

Chinese. 以叶绿素缺乏突变体水稻为材料，研究其光系统蛋白和叶绿素的合成特性，以揭示叶绿素的生物合成及其调控的机理。通过蛋白质电泳、Western 杂交、Northern 杂交以及叶绿素前体物质的测定等来鉴定叶绿素缺乏突变体W1的黄化原因。与野生型相比，叶绿素缺乏突变体W1的叶绿素含量明显减少，与之对应的是其类囊体膜蛋白的减少，特别是光系统 II 捕光色素蛋白 (LHCII) 三聚体含量的急剧减少。Western 杂交进一步表明，W1的LHCII含量仅为野生型的1/3。编码LHCII脱辅基蛋白的cab基因在突变体W1和野生型中转录水平相仿。突变体W1叶绿素合成的前体物质从合成的起始δ-氨基乙酰丙酸（ALA）到原脱植基叶绿素（Pchlide）含量均等于或高于野生型，而脱植基叶绿素（Chlide）、叶绿素a和叶绿素b的含量均显著低于野生型。通过突变体W1和野生型的比较说明，突变体W1 LHCII脱辅基蛋白含量的减少并不是由于cab基因的转录量降低引起的。通过测定叶绿素合成的前体物质初步认为突变体W1叶绿素缺乏的原因是原脱植基叶绿素到脱植基叶绿素的合成效率降低所致。

English. Biosynthesis of chlorophyll comprises a number of challenging topics. Chlorophyll-deficient mutants play an important role in exploring biochemical and molecular aspects of its pathway and regulation. Chlorophyll- deficient rice, W1, was analyzed by methods of green gel electrophoresis, SDS-PAGE, Western blotting, Northern blotting and detecting precursors of chlorophyll synthesis. W1 mutant had a significantly decreased amount of chlorophyll, and so did thylakoid proteins, especially Light-Harvesting-Complex II (LHCII) trimers. Western blotting further revealed that LHCII apoproteins in W1 dropped to 1/3 of its amount in wild type. Northern blotting showed a close transcription ability between W1 and its wild type. The contents of chlorophyll synthesis precursors, from δ-aminolevulinic acid (ALA) to protochlorophyllide (Pchlide), equaled to or were greater than those accumulated in W1. However, its chlorophyllide (Chlide), Chl a and Chl b markedly decreased. Analysis has proved that the reason for decreased LHCII level in W1 is not due to the reduced transcription and its mRNA accumulation, a possible inefficient synthesis from Pchlide to Chlide primarily attributed to the lowered chlorophylls in W1.