Phylogenomic analysis of transcriptomic sequences of mitochondria and chloroplasts for marine red algae (Rhodophyta) in China

The chloroplast and mitochondrion of red algae （Phylum Rhodophyta） may have originated from different endosymbiosis. In this study, we carried out phylogenomic analysis to distinguish their evolutionary lin-eages by using red algal RNA-seq datasets of the 1 000 Plants （1KP） Project and publicly available complete genomes of mitochondria and chloroplasts of Rhodophyta. We have found that red algae were divided into three clades of orders, Florideophyceae, Bangiophyceae and Cyanidiophyceae. Taxonomy resolution for Class Florideophyceae showed that Order Gigartinales was close to Order Halymeniales, while Order Graci-lariales was in a clade of Order Ceramials. We confirmed Prionitis divaricata （Family Halymeniaceae） was closely related to the clade of Order Gracilariales, rather than to genus Grateloupia of Order Halymeniales as reported before. Furthermore, we found both mitochondrial and chloroplastic genes in Rhodophyta under negative selection （Ka/Ks〈1）, suggesting that red algae, as one primitive group of eukaryotic algae, might share joint evolutionary history with these two organelles for a long time, although we identified some dif-ferences in their phylogenetic trees. Our analysis provided the basic phylogenetic relationships of red algae, and demonstrated their potential ability to study endosymbiotic events.     

坛紫菜磷酸烯醇式丙酮酸羧化酶基因的克隆与序列分析

采用同源克隆的方法和RACE技术,从坛紫菜cDNA中获得了磷酸烯醇式丙酮酸羧化酶(PEPC)的序列,该段序列含2538个核苷酸包含一个终止密码子TAG和191 bp的3'端非编码区(UTR),可编码846个氨基酸.该段序列中无跨膜结构和信号肽序列,推导的氨基酸序列中C末端第813位氨基酸是丙氨酸(A),表明是一个C<,...     

Macroalgal assemblages of disturbed coastal detritic bottoms subject to invasive species

Characteristic flora and fauna that are highly sensitive to disturbances colonize coastal detritic bottoms in the Mediterranean Sea. In the present study, a comparison of the assemblage composition and colonization by invasive macroalgae was made between two coastal detritic macrophyte assemblages, one dominated by rhodoliths (free-living non-geniculate Corallinales) and the other dominated by fleshy algae, in an area that has been exposed to important levels of anthropogenic disturbance, mainly pollution (including changed sedimentation regimes) in the recent past (bay of Marseilles, France). In comparison with less strongly impacted Mediterranean regions, the macrophyte assemblages in the bay of Marseilles were characteristic in terms of species identity and richness of coastal detritic macrophyte assemblages. However, extremely low species abundance (cover) was observed. As far as invasive species were concerned, Caulerpa racemosa var. cylindracea was only abundant in the rhodolith assemblage whereas the two invasive Rhodophyta Asparagopsis armata and Womersleyella setacea were mainly found in the fleshy algae assemblage. The seasonality observed in the Rhodolith assemblage seemed to be related to the development of C. racemosa var. cylindracea and did not follow the typical pattern of other Mediterranean assemblages. This study represents the first study of coastal detritic assemblages invaded by C. racemosa var. cylindracea.     

南极红藻Iridaea cordata和Curdiea racovitzae转录组分析及其极端光环境适应相关基因的挖掘

南极红藻具有重要的生态学功能和开发利用价值。南极极端环境赋予了其独特的生理耐受机制,也是发现新基因和代谢途径的理想材料。我们测序分析了南极产胶红藻Iridaea cordata (Turner) Bory和Curdiea racovitzae Hariot的转录组序列,并与其常温近缘种进行了比较,同时挖掘了其与光限制和强紫外线辐射等光环境适应相关的基因。I. cordata和C. racovitzae的转录组序列分别拼接成了14055条和12006条非冗余基因,平均长度分别为1473 bp和1448 bp。在I. cordata转录组中发现多条与绿藻基因同源的捕光复合物LHC基因Lhca2、Lhca6和Lhcb,并且在两种南极红藻中都各发现了1条编码结合岩藻黄质和Chl a/c蛋白的Lhcf基因,目前尚未在其他红藻中发现这类基因。光裂解酶修复紫外线诱导DNA损伤,在I. cordata的转录组序列中发现了6?4光裂解酶,光裂解酶CPD I和CPD II基因,而C. racovitzae转录组序列中仅找到了光裂解酶CPD II基因。尽管南极红藻中这些特有基因的功能有待进一步的验证,但是本文为后续研究红藻的南极极端光环境适应机制提供了方向。     

福建红树林区海藻的分布及季节变化

主要研究了福建省3个红树林区的海藻不同滩面分布的情况、海藻种类组成的季节变化以及不同季节的海藻群落类型.研究表明:(1)福建红树林区海藻在不同滩面分布表现出,红藻较喜荫蔽潮湿的环境,而绿藻适生在光照条件较好生境.(2)由福建红树林区各门海藻种类组成的季节变化来看,蓝藻种数在一年四季没有明显变化规律,红藻四季种数变化幅度不大,而绿藻在不同季节种数有明显变化,春季种数最多,进入夏季后种数逐渐减少,到秋、冬季后种数又开始上升,到第2年春季又达到最多.(3)不同季节福建红树林区海藻群落类型中,优势种主要是红藻,以及一些绿藻.     

Alterations in seawater pH and CO2 affect calcification and photosynthesis in the tropical coralline alga, Hydrolithon sp. (Rhodophyta)

Calcification in the marine environment is the basis for the accretion of carbonate in structures such as coral reefs, algal ridges and carbonate sands. Among the organisms responsible for such calcification are the Corallinaceae (Rhodophyta), recognised as major contributors to the process world-wide. Hydrolithon sp. is a coralline alga that often forms rhodoliths in the Western Indian Ocean. In Zanzibar, it is commonly found in shallow lagoons, where it often grows within seagrass beds and/or surrounded by green algae such as Ulva sp. Since seagrasses in Zanzibar have recently been shown to raise the pH of the surrounding seawater during the day, and since calcification rates are sensitive to pH, which changes the saturation state of calcium carbonate, we measured the effects of pH on photosynthetic and calcification rates of this alga. It was found that pH had significant effects on both calcification and photosynthesis. While increased pH enhanced calcification rates both in the light and in the dark at pH >8.6, photosynthetic rates decreased. On the other hand, an increase in dissolved CO₂ concentration to 26 μmol kg⁻¹ (by bubbling with air containing 0.9 mbar CO₂) caused a decrease in seawater pH which resulted in 20% less calcification after 5 days of exposure, while enhancing photosynthetic rates by 13%. The ecological implications of these findings is that photosynthetically driven changes in water chemistry by surrounding plants can affect calcification rates of coralline algae, as may future ocean acidification resulting from elevated atmospheric CO₂.     

海黍子和脆江蓠对重金属锌、镉富集的比较研究

采用室内培养实验方法,研究了褐藻海黍子(Sargassum muticum)和红藻脆江蓠(Gracilaria chouae)在不同质量浓度的锌和镉溶液里15 d,藻体的生长和体内金属离子含量的变化。结果表明:两种藻的生长速率与暴露溶液金属质量浓度呈负相关,藻体内积累金属离子的量和溶液的金属质量浓度呈正相关,藻体内金属离子的含量均在培养3 d后显著增加,且随着培养时间的延长而持续增加。海黍子和脆江蓠对重金属Zn~(2+)的富集能力明显高于对Cd~(2+)的富集能力,在相同条件下,海黍子对重金属Zn~(2+),Cd~(2+)的积累量明显高于脆江蓠。以上研究结果对利用藻类修复重金属污染的海洋水体能起到一定的指导和参考作用。     

光照和盐度对浒苔类胡萝卜素生物合成的影响

浒苔是一种在“绿潮”灾害中主要参与的绿藻。类胡萝卜素的生物合成是一种维持藻类正常生命活动非常重要的基本的萜类代谢活动。在本研究中,我们首次报告了浒苔2-C-甲基-D-赤藓糖醇4-磷酸（MEP）途径中所有基因的完整序列,这是浒苔中唯一的类胡萝卜素合成途径。随后,我们将这些基因序列与其他物种进行了比较。此外,通过检测三种不同的光照（1 000 lx,5 000 lx和12000 lx）和盐度（12‰,24‰和40‰）培养条件下的类胡萝卜素含量和参与此代谢的关键基因的表达水平差异,我们发现浒苔类胡萝卜素的合成可能受光照和盐度的影响,低光照和高盐度可以促进类胡萝卜素的合成。本研究结果表明：浒苔MEP途径和下游途径中涉及的基因可以在分子水平影响其类胡萝卜素的生物合成。本研究有助于更好地了解这些参与浒苔类胡萝卜素生物合成基因的作用以及环境对这些基因的调控。     

长牡蛎两种engrailed同源基因的鉴定及其与贝壳发育相关性的研究

engrailed基因属于同源异形基因家族成员,在许多动物的分节、附肢发育、神经系统发育和贝壳形成过程中发挥作用。本研究克隆了长牡蛎两个engrailed同源基因,命名为cgi-eng1和cgi-eng2。序列分析表明,两个基因均具备典型engrailed基因保守的5个EH结构域。利用整装原位杂交技术检测了cgi-eng1和cgi-eng2在贝壳形成的关键时期早期D形幼虫时期的表达情况。结果显示,cgi-eng1和cgi-eng2 m RNA高表达于贝壳外缘,可能与早期贝壳形成过程有关。此外,两个基因的在贝壳外缘的表达模式亦有区别,提示两个基因的功能可能存在一定程度的分化。本研究首次系统鉴定了长牡蛎engrailed基因的成员,并发现它们可能均参与幼虫贝壳形成,研究结果有助于加深对贝类早期发育及贝壳形成的理解。     

New finite-gap solutions for the coupled Burgers equations engendered by the Neumann systems

On the tangent bundle TS^N-1 of the unit sphere S^N-1, this paper reduces the coupled Burgers equations to two Neumann systems by using the nonlinearization of the Lax pair, whose Liouville integrability is displayed in the scheme of the r-matrix technique. Based on the Lax matrix of the Neumann systems, the Abel--Jacobi coordinates are appropriately chosen to straighten out the restricted Neumann flows on the complex torus, from which the new finite-gap solutions expressed by Riemann theta functions for the coupled Burgers equations are given in view of the Jacobi inversion.