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Neopyropia katadae is one of the important economic seaweeds in China. A mass of free-living conchocelis is needed in the commercial cultivation of N. katadae. This study aimed to clarify the optimum growth conditions of the free-living conchocelis of N. katadae and its photosynthetic and biochemical response to different temperatures and irradiances, so as to provide the theoretical basis for the formulation of cultivation strategy of free-living conchocelis. The free-living conchocelis exhibited higher growth rate (RGR), net photosynthetic rates (PN), maximum relative electron transport rates (rETRmax), and maximal photochemical efficiency of PS II (Fv/Fm) at 16–20 °C and 60–80 μmol photons m−2 s−1. Light saturation point of the free-living conchocelis is 60.3–85.2 μmol photons m−2 s−1, and low light compensation point is 6.1–13.7 μmol photons m−2 s−1 in the range of 16–25 °C. The greatly reduced values of RGR, PN, Fv/Fm, rETRmax, Y(II), and Ek (minimum saturating irradiance) indicated that damage to the photosynthetic apparatus and photoinhibition occurred in the free-living conchocelis of N. katadae under high temperature of 23–25 °C and high light intensity (100–200 μmol photons m−2 s−1). High values of Fv/Fm and α (initial slope of the RLC) were both observed at low light intensities (10–80 μmol photons m−2 s−1), suggesting that this conchocelis is low light adapted. The content of glutathione, proline, peroxidase, ascorbate peroxidase (APX), and abscisic acid (ABA) all presented at high levels at 10 μmol photons m−2 s−1, indicating that these compounds probably play an important role under low light stress in the free-living conchocelis. High temperature (24 °C) and high light intensities (100–150 μmol photons m−2 s−1) both led to reactive oxygen species accumulation. Compared to the control, the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione reductase) were substantially enhanced at 24 °C and 100 μmol photons m−2 s−1, and ascorbic acid content in 24 °C group was relatively higher, suggesting that these compounds probably play a crucial role in defensive reactions against high-temperature-induced or high light-induced oxidative stress in the conchocelis. Based on these results, it was proposed that the optimal cultivation conditions for free-living conchocelis of N. katadae were at 16–20 °C and 60–80 μmol photons m−2 s−1.

Porphyra dioica is a commercial seaweed consumed all over the world, mostly in the shape of nori sheets used for “sushi” preparation. It is a well-known part of the Asian diet with health benefits, which have been associated, among others, to the high levels of n-3 and n-6 fatty acids in this red alga. However, other highly valued lipids of Porphyra are polar lipids that remain largely undescribed and can have both nutritional value and bioactivity, thus could contribute to the valorization of this seaweed. In this context, the present work aims to identify the lipidome of two life cycle stages of the Atlantic species Porphyra dioica: the early life stage conchocelis produced in an indoor-nursery, and young blades produced outdoors using an integrated multitrophic aquaculture (IMTA) framework. Both the blades (gametophyte) and conchocelis (sporophyte) are commercialized in the food and cosmetics sectors. Liquid chromatography coupled to Q–Exactive high resolution-mass spectrometry (MS) platform was used to gain insight into the lipidome of these species. Our results allowed the identification of 110 and 100 lipid molecular species in the lipidome of the blade and conchocelis, respectively. These lipid molecular species were distributed as follows (blade/conchocelis): 14/15 glycolipids (GLs), 93/79 phospholipids (PLs), and 3/6 betaine lipids. Both life stages displayed a similar profile of GLs and comprised 20:4(n-6) and 20:5(n-3) fatty acids that contribute to n-3 and n-6 fatty acid pool recorded and rank among the molecular species with higher potential bioactivity. PLs’ profile was different between the two life stages surveyed, mainly due to the number and relative abundance of molecular species. This finding suggests that differences between both life stages were more likely related with shifts in the lipids of extraplastidial membranes rather than in plastidial membranes. PLs contained n-6 and n-3 precursors and in both life stages of Porphyra dioica the n-6/n-3 ratio recorded was less than 2, highlighting the potential benefits of using these life stages in human diet to prevent chronic diseases. Atherogenic and thrombogenic indexes of blades (0.85 and 0.49, respectively) and conchocelis (0.34 and 0.30, respectively) are much lower than those reported for other Rhodophyta, which highlights their potential application as food or as functional ingredients. Overall, MS-based platforms represent a powerful tool to characterize lipid metabolism and target lipids along different life stages of algal species displaying complex life cycles (such as Porphyra dioica), contributing to their biotechnological application.

Seaweeds are a recognized source of bioactive compounds and techno-functional ingredients. However, its protein fraction is still underexplored. The aim of this study was to determine the total and free amino acid profile and protein content of four seaweeds species (Porphyra dioica, Porphyra umbilicalis,Gracilaria vermiculophylla, and Ulva rigida) produced in an integrated multi-trophic aquaculture system, while assessing their protein quality. Samples were submitted to acid and alkaline hydrolysis (total amino acids) and to an aqueous extraction (free amino acids) followed by an automated online derivatization procedure, and analyzed by reverse phase-high performance liquid chromatography. Protein-, non-protein and total-nitrogen were quantified by the Kjeldahl method. Crude and true protein contents were estimated based on the nitrogen and amino acid composition. Protein quality was assessed based on the amino acids profile. Porphyra species presented the highest protein content compared to the remaining three seaweed species tested. All samples presented a complete profile of essential amino acids and a high quality protein profile, according to World Health Organization and Food and Agriculture Organization standards. Methionine and tryptophan were the first limiting amino acids in all species. Red species (Porphyra and Gracilaria) presented high levels of free alanine, glutamic, and aspartic acids. The results highlight the potential of using seaweeds as an alternative and sustainable source of protein and amino acids for human nutrition and industrial food processing.

Pyropia haitanensis , an economically cultivated red alga, exhibits both sexual and asexual reproduction. Genetic studies have revealed that the gametophytic blades produced by sexual reproduction are monoecious, while those produced by parthenogenesis of female gametophyte and apogamy of male gametophyte are unisexual. However, identifying the sex of P. haitanensis from different sources at the molecular level is still lacking. In this study, female- and male-specific marker primers were used to amplify the genomic DNA of conchocelis and blades from different sources. The results showed that only a female-specific band was amplified in both conchocelis and blades produced by parthenogenesis, while only a male-specific band was amplified in both conchocelis and blades produced by apogamy. In heterozygous conchocelis produced by sexual reproduction and their subsequent offspring four-color-sectored blades, both male and female-specific bands were amplified. Among the wild blades of P. haitanensis , 83.3% of the individuals exhibited both female- and male-specific bands. These findings confirmed the sex of offspring produced by sexual reproduction, parthenogenesis, and apogamy of P. haitanensis at the molecular level.

We found filamentous structures resembling conchocelis of red algae within the nacreous layer of the Akoya pearl oyster Pinctada fucata shell. Microscopic analyses revealed that these filamentous structures had an autofluorescence and varied in length, occasionally branched, and exhibited diameters ranging from 2 to 5 μm—consistent with previously reported sizes for Bangiales conchocelis. We extracted DNA from organic matrix sheets obtained by decalcifying the shell and performed PCR with primers targeting red algae from the family Bangiales to identify these structures. Sequencing analysis confirmed a 94% match with that of Bangia fuscopurpurea , establishing the presence of Bangia conchocelis within the shell. Conchocelis distributed predominantly near the anterior ear across all examined shells. In 3-year-old oysters, conchocelis filament densities reached approximately 250 filaments per 1 mm 2 , with a broader distribution area than a 2-year-old oyster, where densities were lower, peaking at 35 filaments per 1 mm 2 . Conchocelis distribution was consistent between the left and right shells of the identical oyster. These findings suggest that conchocelis density and distribution expand with oyster growth, providing insights into the age-related dynamics of conchocelis localization in Akoya pearl oyster shells.

The conchocelis life cycle stage of P. dioica represents an unexplored source of bioactive compounds. The aim of this study was to generate and characterise, for the first time, hydrolysates of conchocelis using a specific combination of proteases (Prolyve® and Flavourzyme®). Hydrolysate molecular mass distribution and free amino acid contents were assessed, and the antioxidant activity was determined using a range of in vitro assays. The protein content and the total amino acid profiles of conchocelis were also studied. Conchocelis contained ~25% of protein (dry weight basis) and had a complete profile of essential amino acids. Direct sequential enzymatic treatment modified the profile of the generated compounds, increasing the amount of low molecular weight peptides (<1 kDa). There was a significant improvement in the antioxidant activity of the hydrolysates compared with the control (up to 2.5-fold), indicating their potential as a novel source of antioxidant ingredients.

The temperate genus Porphyra sensu lato has a long history of marine farming. Members of the genus are amongst the most common and economically valuable, commercially cultivated seaweeds on nets in the open sea. Species have a heteromorphic life cycle, alternating between a macroscopic blade and a microscopic, phase. The latter is an endolithic, shell-borne, filamentous thallus called the conchocelis which is cultivated separately within various bivalve shells in shallow ponds, on land. As a crop, its cultivation is accompanied by ever-increasing incidences of pests and diseases of both the blade and conchocelis phases. Serious damage is reported to be caused by the oomycete fungus Pythium (Py.) porphyrae and the chytrid Olpidiopsis spp., which have decreased the productivity of large-scale open sea farms especially in Korea and the northern coast of China. Interestingly, calcium propionate is effective combating oomycete infections. Early detection and development of resistant Porphyra strains, perhaps with some prophylactic, prebiotic treatments of low molecular weight oligoagars and selected probiotic, immune-stimulating bacteria might limit the damaging effects and economic consequences of this disease. In addition, cultivation nets are washed in acid to prevent carry over of disease-causing agents. As with any marine farming activity, epiphytes and grazers can also be issues faced by the farmers, but nothing as serious as the various rotting diseases. A summary of these studies is presented as a guide for rapid responses and applied management techniques for the amelioration of cultivation diseases, grazers, and harmful epiphytes affecting the two distinct phases of commercial Porphyra cultivation.

Microorganisms play important roles in the growth and development of macroalgae. Still, the biodiversity of the epiphytic microbial community associated with the economically important red alga Pyropia haitanensis during the cultivation period remains uncharacterized, especially the effects of P. haitanensis cultivation on the microbial community of surrounding seawater. Here, we isolated epiphytic microbes from P. haitanensis during the thallus stage during oceanic cultivation and the conchocelis stage during industrial cultivation. The dynamic diversity patterns, as determined by 16S and 18S rRNA gene sequencing of the bacterial and fungal communities, respectively, associated with P. haitanensis and seawater in the presence and absence of algal cultivation were investigated. A notable distinction was observed between the microbial communities of seawater with and without P. haitanensis cultivation. Additionally, the alpha-diversity of seawater with P. haitanensis cultivation was significantly greater than without P. haitanensis cultivation. Cyanobacteria were the dominant species in the latter, while Rhodobacteraceae was enriched in the former. Furthermore, there were significant differences in the microbial community of P. haitanensis at the thallus and conchocelis stages. Seawater properties had significant direct effects on the microbial diversity of P. haitanensis and cultivation seawater, but not on non-cultivation seawater. The enriched microbial presence might promote thallus morphogenesis and be beneficial for the growth and development of both the thallus and conchocelis stages. These findings expand our knowledge of the bacteria and fungi that are beneficial for Pyropia nursery seeding and cultivation, as well as the effects of P. haitanensis cultivation on the seawater microbial community.

The modulated chlorophyll fluorescence kinetics of thallus and conchocelis in Porphyra grown under different light intensities were investigated with Water-PAM chlorophyll fluorometer. Results showed that the actual photochemical efficiency of PSII (Yield) decreased with the increasing of light intensity. The calculated minimum saturating irradiance (I sub(k)) from rapid light curves (RLC) of thallus and conchocelis of P. yezoensis and P. haitanensis were less than 150 kmol m super(-2) s super(-1). The results of Yield and I sub(k) indicate Porphyra is one kind of algae adapted to lower light intensity. The I sub(k), which is determined by the interception of the initial slope of RLC (a) with the relative maximum electron transport rate (rETRmax), reflects high light tolerance ability. High PAR increased the I sub(k) of conchocelis of P. haitanensis but not P. yezoensis, which supported the idea that conchocelis of P. haitanensis can tolerance higher PAR than that of P. yezoensis. Conchocelis of both species of Porphyra grown under higher light intensity decreased significantly in Yield, a, and rETRmax; but thallus have little change in the rETRmax, which mean conchocelis and thallus have different response mechanisms to PAR. The results of induce curve indicated that thallus of both species of Porphyra grown under high PAR had higher photochemical quenching (qP) and lower non-photochemical quenching (NPQ) than those grown under low PAR, which suggested the light tolerance of thallus can be improved by high PAR acclimation.

Background Pyropia haitanensis is an economically important mariculture crop in China and is also valuable in life science research. However, the lack of genetic information of this organism hinders the understanding of the molecular mechanisms of specific traits. Thus, high-throughput sequencing is needed to generate a number of transcriptome sequences to be used for gene discovery and molecular marker development. Results In this study, high-throughput sequencing was used to analyze the global transcriptome of P. haitanensis . Approximately 103 million 90 bp paired-end reads were generated using an Illumina HiSeq 2000. De novo assembly with paired-end information yielded 24,575 unigenes with an average length of 645 bp. Based on sequence similarity searches with known proteins, a total of 16,377 (66.64%) genes were identified. Of these annotated unigenes, 5,471 and 9,168 unigenes were assigned to gene ontology and clusters of orthologous groups, respectively. Searching against the KEGG database indicated that 12,167 (49.51%) unigenes mapped to 124 KEGG pathways. Among the carbon fixation pathways, almost all the essential genes related to the C3- and C4-pathways for P. haitanensis were discovered. Significantly different expression levels of three key genes (Rubisco, PEPC and PEPCK) in different lifecycle stages of P. haitanensis indicated that the carbon fixation pathway in the conchocelis and thallus were different, and the C4-like pathway might play important roles in the conchocelis stage. In addition, 2,727 cSSRs loci were identified in the unigenes. Among them, trinucleotide SSRs were the dominant repeat motif (87.17%, 2,377) and GCC/CCG motifs were the most common repeats (60.07%, 1,638). High quality primers to 824 loci were designed and 100 primer pairs were randomly evaluated in six strains of P. haitanensis . Eighty-seven primer pairs successfully yielded amplicons. Conclusion This study generated a large number of putative P. haitanensis transcript sequences, which can be used for novel gene discovery and gene expression profiling analyses under different physiological conditions. A number of the cSSR markers identified can be used for molecular markers and will facilitate marker assisted selection in P. haitanensis breeding. These sequences and markers will provide valuable resources for further P. haitanensis studies.