紫菜壳孢子萌发过程及其世代差异研究

紫菜是一类海洋藻类研究的模式系统，具有重要的经济价值和理论研究意义。本研究基于紫菜的世代交替生活史，对其壳孢子萌发过程进行了研究，并对丝状孢子体与叶状配子体的世代差异进行了分析，主要包括以下三部分： 1） 对紫菜丝状孢子体与叶状配子体的连接枢纽——壳孢子的发育过程及其光影响进行了研究与讨论，发现壳孢子只有在附着后才能形成细胞壁并发育，说明壳孢子的附着是触发了壳孢子细胞壁的形成以及后期发育的开关，亦即附着是触发紫菜世代交替过程中配子体转录组表达的开关；纤维素酶和果胶酶均能抑制壳孢子附着，但影响机制各不相同，推测果胶质主要介导壳孢子的初始附着，而纤维素则与永久附着相关；波长≥580 nm的高强度（200 μmol•m-2•s-1）可见光有利于壳孢子早期发育。 2） 结合现有藻类数据，对坛紫菜丝状孢子体阶段11000 EST数据进行了大规模的生物信息学分析，结果首次发现坛紫菜丝状孢子体中可能存在PCK型C4光合固碳途径，并筛选出44条在紫菜孢子体中表达上调的代表基因。 3） 结合坛紫菜、条斑紫菜、海带和红毛菜，对红藻和褐藻等大型海藻孢子体与配子体阶段代表基因Rubisco的表达与羧化酶活性差异进行了研究分析，结果表明Rubisco的表达量和初始羧化酶活在其配子体中均显著高于其孢子体世代，即与藻体不同世代的相对复杂度无关，而与染色体倍性相关，说明Rubisco的世代差异极有可能与染色体倍性相连锁，因而可能是海藻世代交替过程中的重要功能基因。

Porphyra，a model system of marine algae，is economically important and valuable for theoretical study. Based on the dimorphic life cycle of porphyra，this study focused on the germinating process of conchospore and the differences between the filamentous sporophyte and leafy gametophyte，and contained three parts: 1) Germinating process of conchospore which linked the filamentous sporophyte and the leafy gametophyte of Porphyra，and influences of light on the process were studied and discussed. Only the attached conchospores generated cell wall and developed into leafy gametophyte，which indicated that the attachment was the trigger of the cell wall formation and the further development. Either cellulase or pectolase can prohibit the attachment，however they acted in the different ways，which indicated that the pectin played a crucial role in the initial attachment as the cellulose did in the permanent attachment. High intensity（200 μmol•m-2•s-1）visible light with wave-length ≥580 nm facilitated the division rate of conchospores. 2) Large-scale bioinformatical analyses were performed in the combination of 11000 ESTs from filamentous sporophyte of Porphyra haitanensis and all the available algal data. PCK-type C4 carbon fixation pathway was suggested in P. haitanensis sporophyte and 44 gene candidates up-regulated in Porphyra sporophyte were screened. 3) The differences of Rubisco content and its carboxylase activity between sporophyte and gametophyte of Porphyra yezoensis，P. haitanensis，Laminaria japonica and Bangia fuscopurpurea were studied. It showed that Rubisco content and its initial carboxylase activity were notably higher in their gametophyte than those in their sporophyte. That was to say，Rubisco content and its initial carboxylase activity were not relevant to the complexity but likely to the ploidy of the generation in the macroalgae. It was speculated that Rubisco played crucial roles during the transition of generations of macroalgae.