Search Results (10)

The transition from conchocelis to conchosporangia in Pyropia haitanensis represents a pivotal stage in its life cycle. As a commercially vital red alga, P. haitanensis plays a dominant role in global nori production. The transition governing its sporulation efficiency is pivotal for aquaculture success, yet the underlying regulatory mechanisms, especially their integration with metabolic cues such as polyamines, remain poorly understood. This study uncovered a critical role for the polyamine spermine (SPM) in promoting conchosporangial formation, mediated through the signaling activity of superoxide anions (O₂·⁻). Treatment with SPM markedly elevated O₂·⁻ levels, an effect that was effectively inhibited by the NADPH oxidase inhibitor diphenyliodonium chloride (DPI), underscoring the role of O₂·⁻ as a key signaling molecule. Transcriptomic analysis revealed that SPM enhanced photosynthesis, carbon assimilation, and respiratory metabolism, while simultaneously activating antioxidant enzymes, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), to regulate hydrogen peroxide (H₂O₂) levels and maintain redox homeostasis. Furthermore, SPM upregulated genes associated with photosynthetic carbon fixation and the C₂ oxidative photorespiration pathway, supplying the energy and metabolic resources necessary for this developmental transition. These findings suggested that SPM orchestrated O₂·⁻ signaling, photosynthetic activity, and antioxidant defenses to facilitate the transition from conchocelis to conchosporangia in P. haitanensis. Full article

Pyropia haitanensis (T.J. Chang and B.F. Zheng) undergoes periodic dehydration and rehydration cycles, necessitating robust adaptive mechanisms. Despite extensive research on its physiological responses to desiccation stress, the comprehensive metabolic pathways and recovery mechanisms post-rehydration remain poorly understood. This study investigated the metabolic responses of P. haitanensis to varying degrees of desiccation stress using LC-MS and UPLC-MS/MS. Under mild dehydration, the thallus primarily accumulated sugars and proline, while moderate and severe dehydration triggered the accumulation of additional osmoprotectants like alanine betaine and trehalose to maintain turgor pressure and water retention. Concurrently, the alga activated a potent antioxidant system, including enzymes and non-enzymatic antioxidants, to counteract the increased reactive oxygen species levels and prevent oxidative damage. Hormonal regulation also plays a crucial role in stress adaptation, with salicylic acid and jasmonic acid upregulating under mild dehydration and cytokinins and gibberellin GA₁₅ accumulating under severe stress. Rehydration triggered the recovery process, with indole acetic acid, abscisic acid, and jasmonic acid promoting rapid cell recovery. Additionally, arachidonic acid, acting as a signaling molecule, induced general stress resistance, facilitating the adaptation of the thallus to the dynamic intertidal environment. These findings reveal P. haitanensis’ metabolic adaptation strategies in intertidal environments, with implications for enhancing cultivation and stress resistance in this economically important seaweed. Full article

The possible regulatory effects of C2H2 zinc finger proteins, which are important transcription factors, on intertidal seaweed responses to abiotic stress are unclear. This study was conducted to comprehensively analyze the C2H2 gene family of a representative intertidal seaweed species (Pyropia haitanensis) and clarify its genomic characteristics and biological functions. A total of 107 PhC2H2 zinc finger protein-encoding genes distributed on five P. haitanensis chromosomes were identified and divided into three subgroups. The expression levels of 85, 61, 58, 45, and 41 PhC2H2 genes responded in the maturation of filaments, high-temperature, salt, low-irradiance, and dehydration stress, respectively. The PhC2H2 gene family was conserved during Porphyra evolution, with no indications of large-scale genome-wide replication events. On average, PhC2H2 genes had more transposable element (TE) insertions than Pyropia yezoensis and Porphyra umbilicalisC2H2 genes, suggesting that TE insertions may have been the main driver of PhC2H2 gene family expansion. A key gene (PhC2H2.94) screened following a quantitative trait locus analysis was significantly responsive to high-temperature stress and was associated with photosynthesis, peroxisomes, the ubiquitin proteasome pathway, and the endoplasmic reticulum-related protein processing pathway, which contribute to the stress tolerance of P. haitanensis. Additionally, PhC2H2.94 transgenic Chlamydomonas reinhardtii exhibited increased tolerance to heat stress. This study provides new insights and genetic resources for characterizing the molecular mechanism underlying intertidal seaweed responses to abiotic stresses and breeding stress-resistant macroalgae. Full article

Lipoxygenases (LOXs) from lower organisms have substrate flexibility and function versatility in fatty acid oxidation, but it is not clear how these LOXs acquired the ability to execute multiple functions within only one catalytic domain. This work studied a multifunctional LOX from red alga Pyropia haitanensis (PhLOX) which combined hydroperoxidelyase (HPL) and allene oxide synthase (AOS) activity in its active pocket. Molecular docking and site-directed mutagenesis revealed that Phe642 and Phe826 jointly regulated the double peroxidation of fatty acid, Gln777 and Asn575 were essential to the AOS function, and the HPL activity was improved when Asn575, Gln777, or Phe826 was replaced by leucine. Phylogenetic analysis indicated that Asn575 and Phe826 were unique amino acid sites in the separated clades clustered with PhLOX, whereas Phe642 and Gln777 were conserved in plant or animal LOXs. The N-terminal START/RHO_alpha_C/PITP/Bet_v1/CoxG/CalC (SRPBCC) domain of PhLOX was another key variable, as the absence of this domain disrupted the versatility of PhLOX. Moreover, the functions of two homologous LOXs from marine bacterium Shewanella violacea and red alga Chondrus crispus were examined. The HPL activity of PhLOX appeared to be inherited from a common ancestor, and the AOS function was likely acquired through mutations in some key residues in the active pocket. Taken together, our results suggested that some LOXs from red algae attained their versatility by amalgamating functional domains of ancestral origin and unique amino acid mutations. Full article

MYB transcription factors are one of the largest transcription factor families in plants, and they regulate numerous biological processes. Red algae are an important taxonomic group and have important roles in economics and research. However, no comprehensive analysis of the MYB gene family in any red algae, including Pyropia yezoensis, has been conducted. To identify the MYB gene members of Py. yezoensis, and to investigate their family structural features and expression profile characteristics, a study was conducted. In this study, 3 R2R3-MYBs and 13 MYB-related members were identified in Py. yezoensis. Phylogenetic analysis indicated that most red algae MYB genes could be clustered with green plants or Glaucophyta MYB genes, inferring their ancient origins. Synteny analysis indicated that 13 and 5 PyMYB genes were orthologous to Pyropia haitanensis and Porphyra umbilicalis, respectively. Most Bangiaceae MYB genes contain several Gly-rich motifs, which may be the result of an adaptation to carbon limitations and maintenance of important regulatory functions. An expression profile analysis showed that PyMYB genes exhibited diverse expression profiles. However, the expression patterns of different members appeared to be diverse, and PyMYB5 was upregulated in response to dehydration, low temperature, and Pythium porphyrae infection. This is the first comprehensive study of the MYB gene family in Py. Yezoensis and it provides vital insights into the functional divergence of MYB genes. Full article

Pyropia haitanensis, one of the most economically and ecologically important seaweed species, is often exposed to persistent or transient low irradiance (LI), resulting in limited yield and quality. However, the mechanisms mediating P. haitanensis responses to LI are largely unknown. In this study, LI-tolerant (LIT) and LI-sensitive (LIS) P. haitanensis strains were compared regarding their physiological and transcriptomic changes induced by 1 and 4 days of LI (5 μmol photons/m²·s). The results indicated that the inhibition of photomorphogenesis and decreases in photosynthesis and photosynthetic carbon fixation as the duration of LI increased are the key reasons for retarded blade growth under LI conditions. A potential self-amplifying loop involving calcium signaling, phosphatidylinositol signaling, reactive oxygen species signaling, and MAPK signaling may be triggered in blades in response to LI stress. These signaling pathways might activate various downstream responses, including improving light energy use, maintaining cell membrane stability, mitigating oxidative damage, to resist LI stress. Additionally, the LIT strain maintained transcriptional homeostasis better than the LIS strain under LI stress. Specifically, photosynthesis and energy production were relatively stable in the LIT strain, which may help to explain why the LIT strain was more tolerant to LI stress than the LIS strain. The findings of this study provide the basis for future investigations on the precise mechanisms underlying the LI stress tolerance of P. haitanensis. Full article

Pyropia haitanensis is an important laver species in China. Its quality traits are closely related to the content of glutamic acid. Glutamate dehydrogenase (GDH) is a crucial enzyme in the glutamic acid metabolism. In this study, two GDH genes from P. haitanensis, PhGDH1 and PhGDH2, were cloned and successfully expressed in Escherichia coli. The in vitro enzyme activity assay demonstrated that the catalytic activity of PhGDHs is mainly in the direction of ammonium assimilation. The measured K_m values of PhGDH1 for NADH, (NH₄)₂SO₄, and α-oxoglutarate were 0.12, 4.99, and 0.16 mM, respectively, while the corresponding K_m values of PhGDH2 were 0.02, 3.98, and 0.104 mM, respectively. Site-directed mutagenesis results showed that Gly¹⁹³ and Thr³⁶¹ were important catalytic residues for PhGDH2. Moreover, expression levels of both PhGDHs were significantly increased under abiotic stresses. These results suggest that PhGDHs can convert α-oxoglutarate to glutamic acid, and enhance the flavor and stress resistance of P. haitanensis. Full article

Oct-1-en-3-ol has been studied among oxylipins as a global metabolome that induce the defense of marine algae. The present short review summarized the research of oct-1-en-3-ol as the stress response molecule in marine algae including different aspects: (i) its biosynthesis from fatty acids; (ii) its distribution in marine algae; (iii) a direct effect of oct-1-en-3-ol on microorganisms infecting the thalli; (iv) an indirect communication molecule for alga-alga signaling; and (v) as an inducer that initiates the defense response of algae. Full article

Seaweeds have been verified to effectively reduce the nutrients of aquaculture wastewater, and to increase the economic output when commercially valuable species are utilized. Pyropia/Porphyra/Neopyropia/Neoporphyra species are important seafood resources globally, and their growth and bioremediation capacities are affected by diverse biotic and abiotic stressors. In this study, we investigated the effects of desiccation (0, 1, 2, 4, and 6 h of air exposure), water velocity (0.1, 0.2, and 0.5 m s⁻¹), and the nitrogen limitation period (1, 2, and 3 d) on the relative growth rates (RGR) and nutrient removal rates of Neoporphyrahaitanensis and Neoporphyradentata. The RGRs and NO₃-N removal rates of the two species decreased significantly with increasing desiccation periods. A higher water velocity of 0.5 m s⁻¹ had a greater negative impact on the RGRs and NO₃-N and PO₄-P removal rates than 0.1 and 0.2 m s⁻¹. N. haitanensis exhibited a greater tolerance to water motion than N. dentata. Additionally, the RGRs and NO₃-N and PO₄-P removal rates were significantly different among the nitrogen limitation periods. N. haitanensis and N. dentata exhibited different nitrogen usage strategies after nitrogen limitation and recovery. These results provide valuable information relating to the excessive nutrient removal from aquaculture wastewater by Neoporphyra species. Full article

The present study utilizes polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis using partial plastid rbcL and mitochondrial trnC–trnP gene sequences to distinguish the six representative Pyropia species produced via mariculture in Korea. The rbcL, trnC, and trnP sequences of 15 Pyropia species from the NCBI database were aligned to determine specific restriction enzyme sites of the six Pyropia species. To confirm the presence of restriction sites of eight enzymes, PCR amplicons were digested as follows: a 556 bp fragment within the rbcL region of chloroplast DNA was confirmed in P. yezoensis using BglI, whereas Tth111I, AvaII, BsrI, and BsaAI enzymes produced fragments of 664, 271, 600, and 510 bp, respectively, from the rps11–trnG region of mitochondrial DNA in P. seriata, P. dentata, P. suborbiculata, and P. haitanensis. In the case of P. pseudolinearis, HindIII, SacII, and SphI enzymes each had two cleavage sites, at positions 174 and 825, 788 and 211, and 397 and 602 bp, respectively. All six species were successfully distinguished using these eight restriction enzymes. Therefore, we propose that PCR-RFLP analysis is an efficient tool for the potential use of distinguishing between the six Pyropia species cultivated via mariculture in Korea. Full article