Functional Characterization of the First Bona Fide Phytoene Synthase in Red Algae from Pyropia yezoensis.

The formation of phytoene by condensing two geranylgeranyl diphosphate molecules catalyzed by phytoene synthase (PSY) is the first committed and rate-limiting step in carotenoid biosynthesis, which has been extensively investigated in bacteria, land plants and microalgae. However, this step in macroalgae remains unknown. In the present study, a gene encoding putative phytoene synthase was cloned from the economic red alga Pyropia yezoensis-a species that has long been used in food and pharmaceuticals. The conservative motifs/domains and the tertiary structure predicted using bioinformatic tools suggested that the cloned PyPSY should encode a phytoene synthase; this was empirically confirmed by pigment complementation in E. coli. This phytoene synthase was encoded by a single copy gene, whose expression was presumably regulated by many factors. The phylogenetic relationship of PSYs from different organisms suggested that red algae are probably the progeny of primary endosymbiosis and plastid donors of secondary endosymbiosis.

A molecular phylogeny of the bladed Bangiales (Rhodophyta) in China provides insights into biodiversity and biogeography of the genus Pyropia.

A molecular taxonomic study was undertaken for the first time of the bladed Bangiales of the mainland coast of China (Northwest Pacific) based on sequence data of 201 plastid rbcL and 148 nuclear 18S sequences of historical and contemporary specimens. The results revealed that only one genus of bladed Bangiales, Pyropia, was present along Chinese coast. Species delimitation was determined using two empirical methods: the Automatic Barcode Gap Discovery (ABGD) and General Mixed Yule Coalescence (GMYC) coupled with detection of monophyly in tree reconstruction. At least fourteen species of Pyropia were recovered. Six species were confirmed that had been recorded previously based on morphology (Py. suborbiculata, Py. yezoensis, Py. haitanensis, Py. katadae, Py. tenera and Py. acanthophora), three species were recorded from China for the first time (Py. kinositae, Py. pseudolinearis and Py. tanegashimensis), and five cryptic species that did not match any molecular sequences were also discovered. The phylogeny of the concatenated rbcL and 18S dataset resolved three singletons and four clades. Each clades has a strong trend towards occupying a biogeographic region, but they are not confined to them. A transoceanic and antitropical pattern of distribution was found for Pyropia at both the subgeneric and species level. This together with high biodiversity (ca. 30% of all known Pyropia species) indicates that the Northwest Pacific might act as a centre of origin for modern distribution of Pyropia since the early Cenozoic.

Quantitative, molecular and growth analyses of Ulva microscopic propagules in the coastal sediment of Jiangsu province where green tides initially occurred.

From 2007 to 2011, large-scale green tides formed by unattached filamentous alga, Ulva prolifera in Ulva linza-procera-prolifera complex, have initially occurred in Jiangsu coasts of China. The real niche or the substrate(s) on which U. prolifera attaches before it starts to float is still under debate. However, great numbers of Ulva propagules would be supposed to exist in the microscopic, overwintering stage for the next spring's bloom in coastal environments. This study was designed to confirm the above prediction and investigate abundance, species composition and growth characteristics of Ulva propagules in the sediments. Quantification result showed that Ulva propagules widely distributed in the sediments and the abundance of these isolates did not change much over a 3-month testing period at low temperature in darkness. Molecular data based on three DNA markers revealed that four Ulva species existed in the sediments, among which green-tide forming alga, U. prolifera, was included. Elevated levels of temperature, irradiance as well as nutrients in seawater greatly facilitated recovery and growth of propagules. Results of this investigation indicated the possibility of microscopic propagules turning directly into floating biomass in season when temperature, irradiance and nutrients together meet the required levels in questioned coastal water area.