Journal of Phycology最新文献

The northward shift of Pyropia yezoensis aquaculture required the breeding of germplasms with tolerance to the oxidative stress due to the high light conditions of the North Yellow Sea area. The MPV17/PMP22 family proteins were identified as a molecule related to reactive oxygen species (ROS) metabolism. Here, one of the MPV17 homolog genes designated as PyM-LP2 was selected for functional identification by introducing the encoding sequence region/reverse complementary fragment into the Py. yezoensis genome. Although the photosynthetic activity, the respiratory rate, and the ROS level in wild type (WT) and different gene-transformed algal strains showed similar levels under normal conditions, the overexpression (OE) strain exhibited higher values of photosynthesis, respiration, and reducing equivalents pool size but lower intracellular ROS production under stress conditions compared with the WT. Conversely, all the above parameters showed opposite variation trends in RNAi strain as those in the OE strain. This implied that the PyM-LP2 protein was involved in the mitigation of the oxidative stress. Sequence analysis revealed that this PyM-LP2 protein was assorted to peroxisomes and might serve as a poring channel for transferring malate (Mal) to peroxisomes. By overexpressing PyM-LP2, the transfer of Mal from chloroplasts to peroxisomes was enhanced under stress conditions, which promoted photorespiration and ultimately alleviated excessive reduction of the photosynthetic electron chain. This research lays the groundwork for the breeding of algae with enhanced resistance to oxidative stresses.

Four species of the genus Wrangelia are presently known from the western Atlantic Ocean: W. argus, W. bicuspidata, W. penicillata, and W. gordoniae, with the first three historically being reported from Bermuda. Morphological and molecular barcode (COI-5P) and phylogenetic analyses used in this study (SSU, LSU, rbcL) indicated eight species groupings of Wrangelia in Bermuda, excluding two of the historically recognized species, retaining only W. argus while adding seven new species, of which six are formally described. What had been historically reported as W. penicillata from Bermuda was shown to be distinct from Mediterranean Sea specimens (type locality) and was shown to be a mixture of W. hesperia sp. nov. and W. incrassata sp. nov. Along with these two, three other new species (W. laxa sp. nov., W. ryancraigii sp. nov., and W. secundiramea sp. nov.) have complete rhizoidal cortication tightly covering axial cells of indeterminate axes below the apices, distinguishing them from the two local incompletely corticated congeners W. argus and W. abscondita sp. nov., the latter a morphologically cryptic sister species with W. bicuspidata from the Caribbean Sea. Only one of the new species, W. ryancraigii, has thus far been observed in the mesophotic zone off the Bermuda platform, and it is morphologically cryptic with the euphotic zone's W. laxa.

Biogeographic structure in marine protist communities is shaped by a combination of dispersal potential and environmental selection. High-throughput sequencing and global sampling efforts have helped better resolve the composition and functions of these communities in the world's oceans using both molecular and visual methods. However, molecular barcoding data are critically lacking across the Indo-Pacific, a region widely considered the epicenter of marine biodiversity. To fill this gap, we characterized protist communities in four sampling regions across Indonesia that represent the latitudinal, longitudinal, and human population gradients of the region: Lombok, Wakatobi, Misool, and Waigeo. We show high spatial structuring in marine protist communities across Indonesia, and biotic factors appear to play little role in driving this observed structure. Our results appear to be driven by abiotic factors linked to surface current patterns across the Indo-Pacific as a result of: (1) a choke point in circulation at the Indonesian Throughflow leading to low diatom diversity in Lombok, Wakatobi, and Misool; (2) an increase in nutrient availability at the edge of the Halmahera Eddy in Waigeo, leading to an increase in diatom diversity; and/or (3) seasonal variations in protist communities in line with shifts in velocity of the Indonesian Throughflow. Overall, our results highlight the importance of abiotic factors in shaping protist communities on broad geographic scales over biotic, top-down pressures, such as grazing from higher trophic levels.

Diatoms are key components of freshwater ecosystems and are regularly used for paleolimnological reconstructions, in which defining species optima and tolerances is fundamental for interpreting assemblage shifts in a sediment record. Here, we examined responses of diatoms across three major environmental gradients—dissolved inorganic carbon (range: 0.1–230.5 mg · L⁻¹), total phosphorus (range: 3–326 μg · L⁻¹), and maximum lake depth (range: 0.9–55.0 m)—taken from 158 lakes from across Canada. The lakes were sampled as part of the LakePulse Network, which conducted a standardized sampling of lakes spanning 12 Canadian ecozones. Hierarchical logistic regression was used to model the species responses of 37 common taxa, and species optima and tolerances were calculated with weighted average modeling. The most common response detected was the symmetrical unimodal model, suggesting we likely captured the full environmental ranges for many species, although skewed unimodal responses were also common. Indicator species analyses identified taxa with high predictive values and fidelities to particular ecozones, with high-nutrient-adapted taxa such as Stephanodiscus spp. and Cyclotella meneghiniana characteristic of the agriculturally productive Prairie region. The Prairies stood out in the dataset as the region with the most unique flora from the local contribution to beta diversity analysis. Overall, the autecological data provided by our study will allow for improved interpretations of paleolimnological records and other biomonitoring efforts, addressing management concerns and contributing to a better understanding of our changing environment.

Phytoplankton cells are now recognized as dynamic entities rather than as passive and isolated particles because they can actively modulate impacts of selection factors (nutrients, light, turbidity, and mixing) through a wide range of adaptations. Cell shape and/or chain length modulation is one of these processes but has predominantly been studied as an adaptation or an acclimatation to a specific growth limitation (light, nutrients, predation, etc.). In this study we have demonstrated that cell shape and size may have greater roles than previously known in phytoplankton ecology and species adaptation by permitting cell-to-cell signaling and more complex ecological processes that result from it. By exploring microscale biophysical interactions that lead to specific cell reorientation processes, we demonstrated that cell geometry not only modulates cell sinking rates but can also provide fast sensor responses to the cells' environment. Although gyrotaxis has been described in detail for motile phytoplankton cells, our findings illustrate that the reorientation process described here can occur even in non-motile cells within their natural environment. An additional consistent behavior was also recently described for a diatom species (Pseudo-nitzschia delicatessima), and with this study, we extend this observation to Pseudo-nitzschia pungens and Pseudo-nitzschia fraudulenta. Our observations emphasize the generality of this process, which adds a new level of complexity to our understanding of cellular interactions and their network of sensors.

Tran, Q. D., Neu, T. R., Sultana, S., Giebel, H.-A., Simon, M., & Billerbeck, S. (2023). Distinct glycoconjugate cell surface structures make the pelagic diatom Thalassiosira rotula an attractive habitat for bacteria. Journal of Phycology, 59, 309–322. https://doi.org/10.1111/jpy.13308

In the above article, the first author name was incorrectly published as Tran Quoc Den and has been corrected as follows: ‘Quoc Den Tran’.

The updated author byline is as follows

Quoc Den Tran | Thomas R. Neu | Sabiha Sultana | Helge-A. Giebel | Meinhard Simon | Sara Billerbeck

The published article has also been corrected to reflect the changes.

We apologize for this error.

Sex is a crucial process that has molecular, genetic, cellular, organismal, and population-level consequences for eukaryotic evolution. Eukaryotic life cycles are composed of alternating haploid and diploid phases but are constrained by the need to accommodate the phenotypes of these different phases. Critical gaps in our understanding of evolutionary drivers of the diversity in algae life cycles include how selection acts to stabilize and change features of the life cycle. Moreover, most eukaryotes are partially clonal, engaging in both sexual and asexual reproduction. Yet, our understanding of the variation in their reproductive systems is largely based on sexual reproduction in animals or angiosperms. The relative balance of sexual versus asexual reproduction not only controls but also is in turn controlled by standing genetic variability, thereby shaping evolutionary trajectories. Thus, we must quantitatively assess the consequences of the variation in life cycles on reproductive systems. Algae are a polyphyletic group spread across many of the major eukaryotic lineages, providing powerful models by which to resolve this knowledge gap. There is, however, an alarming lack of data about the population genetics of most algae and, therefore, the relative frequency of sexual versus asexual processes. For many algae, the occurrence of sexual reproduction is unknown, observations have been lost in overlooked papers, or data on population genetics do not yet exist. This greatly restricts our ability to forecast the consequences of climate change on algal populations inhabiting terrestrial, aquatic, and marine ecosystems. This perspective summarizes our extant knowledge and provides some future directions to pursue broadly across micro- and macroalgal species.

Samarium (Sm) is a rare-earth element recently included in the list of critical elements due to its vital role in emerging new technologies. With an increasing demand for Sm, microbial bioremediation may provide a cost-effective and a more ecologically responsible alternative to remove and recover Sm. We capitalized on a previously selected Chlamydomonas reinhardtii strain tolerant to Sm (1.33 × 10⁻⁴ M) and acidic pH and carried out settling selection to increase the Sm uptake performance. We observed a rapid response to selection in terms of cellular phenotype. Cellular size decreased and circularity increased in a stepwise manner with every cycle of selection. After four cycles of selection, the derived CSm4 strain was significantly smaller and was capable of sequestrating 41% more Sm per cell (1.7 × 10⁻⁰⁵ ± 1.7 × 10⁻⁰⁶ ng) and twice as much Sm in terms of wet biomass (4.0 ± 0.4 mg Sm · g⁻¹) compared to the ancestral candidate strain. The majority (~70%) of the Sm was bioaccumulated intracellularly, near acidocalcisomes or autophagic vacuoles as per TEM-EDX microanalyses. However, Sm analyses suggest a stronger response toward bioabsorption resulting from settling selection. Despite working with Sm and pH-tolerant strains, we observed an effect on fitness and photosynthesis inhibition when the strains were grown with Sm. Our results clearly show that phenotypic selection, such as settling selection, can significantly enhance Sm uptake. Laboratory selection of microalgae for rare-earth metal bioaccumulation and sorption can be a promising biotechnological approach.