Proteomic comparison of etioplast and chloroplast protein complexes

Angiosperms grown in darkness develop etioplasts during skotomorphogenesis. It is well known that etioplasts accumulate large quantities of protochlorophyllideoxidoreductase, are devoid of chlorophyll and are the site to assemble the photosynthetic machinery during photomorphogenesis. Proteomic investigation of the membrane protein complexes by Native PAGE, in combination with CyDye labelling and mass spectrometric analysis revealed that etioplasts and chloroplasts share a number of membrane protein complexes characteristic for electron transport, chlorophyll and protein synthesis as well as fatty acid biosynthesis. The complex regulatory function in both developmental states is discussed.     

Photoactivation of the Water-Oxidation System in Isolated Intact Chloroplasts Prepared from Wheat Leaves Grown under Intermittent Flash Illumination

Photoactivation of the latent oxygen-evolving system in intact chloroplasts isolated from wheat (Triticum aestivum L.) leaves grown under intermittent flash illumination was investigated, and the following results were obtained: (a) The water-oxidation activity generated on illuminating the isolated intact chloroplasts was as high as that generated in intact leaves, indicating that all the machinery necessary for the activity generation is assembled within intact chloroplasts. (b) The generation of water-oxidation activity was accompanied by enhancement of the activity of diphenylcarbazide-oxidation, and both processes share the same photochemical reaction but with respective rate-limiting dark reactions of different efficiencies. (c) A23187, an ionophore for divalent cations, strongly inhibited the generation of water-oxidation activity but did not affect the activity once generated, which suggested that Mn atoms in the chloroplasts are susceptible to the ionophore before photoactivation but turn immune after photoactivation. (d) The generation of water-oxidation activity was not affected by the inhibitors of ATP formation and CO(2) fixation, but was inhibited by nitrite, methylviologen and phenylmercuric acetate which suppress or inhibit the reduction of ferredoxin in intact chloroplasts. It was inferred that some factor(s) probably present in stroma to be reduced by PSI photoreaction is involved in the process of photoactivation.     

酵母转录调控协作网络的分析

协作网通常被用于描述各种社会关系,相似的概念也可以应用到转录调控网络的研究中.针对被调控基因共享转录因子的相似性,可以建立一个被调控基因协作网,同样,根据转录因子调控基因的相似性可以建立一个相对较小的转录因子协作网.对被调控基因协作网的聚类研究发现,大部分的类都显著地富集一个或者多个GO功能注释.进一步的结果分析发现某些GO注释的基因更倾向于共享相似的调控机制.这表明,在协作网中,相对简单的调控机制相似性能捕捉生物功能相关的信息.并且,将在二部图分析中使用的概念--"异常点"引入到协作网的分析中,发现协作网的异常点和致死基因有相关性.综上所述,协作网的方法是分析转录调控网络的一个有用的补充.