Shen Songdong, Zhang Gaochuan, Li Yanyan, Wang Li, Xu Pu, Yi Lefei
Department of Cell Biology, School of Biology and Basic Medical Sciences, Soochow University, Suzhou City, Jiangsu Province, 215123, P, R, China.
BMC Res Notes. 2011 Oct 20;4:428. doi: 10.1186/1756-0500-4-428.
Porphyra yezoensis Ueda is one of the most important edible seaweed, with a dimorphic life cycle which consists of gametophyte as macroscopical blade and sporophyte as microscopic filamentous. Conspicuous differences exist in the two generations, such as morphology, cell structure, biochemistry, physiology, and so on. The developmental process of Porphyra yezoensis has been studied thoroughly, but the mechanism is still ambiguous and few studies on genetic expression have been carried out.In this study, the suppression subtractive hybridization (SSH) method conducted to generate large-scale expressed sequence tags (EST) is designed to identify gene candidates related to the morphological and physiological differences between the gametophytic and sporophytic generations of Porphyra yezoensis Ueda.
Each 300 clones of sporophyte and gametophyte cells were dipped onto the membrane for hybridization. The result of dot-blot suggested there were 222 positive clones in gametophyte library and 236 positive clones in sporophyte library. 383 positive clones of strongest signals had been sequenced, and 191 EST sequences of gametophyte and 192 of sporophyte were obtained.A total of 196 genes were obtained, within which 104 genes were identified from the gametophyte and 92 from the sporophyte. Thirty-nine genes of the gametophyte and 62 genes of the sporophyte showed sequence similarity to those genes with known or putative functions which were classified according to their putative biological roles and molecular functions. The GO annotation showed about 58% of the cellular component of sporophyte and gametophyte cells were mainly located in cytoplasm and nucleus. The special genes were located in Golgi apparatus, and high expression in plastid, ribosome and endoplasmic reticulum. The main biological functions of gametophyte cells contributed to DNA repair/replication, carbohydrate metabolism, transport and transcription, especially in response to heat and oxidative stress. The sporophyte cell expresses more genes in transcription, transport, carbohydrate metabolism, particularly in signal transduction, DNA and protein modification, protein and nucleotide metabolism. Four genes are expressed on both gametophyte and sporophyte cells and eighteen genes have not been annotated.
According to the information of GO annotation, the gametophyte tends to growth and self- protection while the sporophyte tends to be more active in development. Interpretation of the differentially expressed genes revealed new insights into the molecular processes of the generation alternation of Porphyra yezoensis. Further investigation are needed due to insufficiency of functional genes research and indeterminancy of the functions of many sequences.
条斑紫菜是最重要的可食用海藻之一，具有双态生命周期，包括宏观叶片状的配子体和微观丝状的孢子体。这两个世代存在明显差异，如形态、细胞结构、生物化学、生理学等方面。条斑紫菜的发育过程已得到充分研究，但其机制仍不明确，且关于基因表达的研究较少。在本研究中，采用抑制性消减杂交（SSH）方法生成大规模表达序列标签（EST），旨在鉴定与条斑紫菜配子体和孢子体世代形态和生理差异相关的候选基因。
将孢子体和配子体细胞各300个克隆点样到膜上进行杂交。斑点杂交结果表明，配子体文库中有222个阳性克隆，孢子体文库中有236个阳性克隆。对383个信号最强的阳性克隆进行了测序，获得了191个配子体EST序列和192个孢子体EST序列。共获得196个基因，其中104个基因来自配子体，92个基因来自孢子体。配子体的39个基因和孢子体的62个基因与已知或推测功能的基因具有序列相似性，这些基因根据其推测的生物学作用和分子功能进行分类。基因本体（GO）注释显示，孢子体和配子体细胞约58%的细胞成分主要位于细胞质和细胞核中。特殊基因位于高尔基体中，在质体、核糖体和内质网中高表达。配子体细胞的主要生物学功能有助于DNA修复/复制、碳水化合物代谢、转运和转录，特别是对热和氧化应激的响应。孢子体细胞在转录、转运、碳水化合物代谢方面表达更多基因，特别是在信号转导、DNA和蛋白质修饰、蛋白质和核苷酸代谢方面。有4个基因在配子体和孢子体细胞中均有表达，18个基因未得到注释。
根据GO注释信息，配子体倾向于生长和自我保护，而孢子体在发育方面更活跃。对差异表达基因的解读揭示了条斑紫菜世代交替分子过程的新见解。由于功能基因研究不足以及许多序列功能的不确定性，还需要进一步研究。
