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opencc-zeroDec 2020View details →

Reappraising plastid markers of the red algae for phylogenetic community ecology in the gnomic era

Selection of appropriate genetic markers to quantify phylogenetic diversity is crucial for phylogenetic community ecology studies. Yet, systematic evaluation of marker genes for this purpose is scarcely done. Recently, the combined effort of the phycological community has produced a rich plastid genome resource with taxonomic representation spanning all of the major lineages of the red algae (Rhodophyta). As a proof-of-concept study, we leverage this resource to develop and apply a phylogenomic strategy to seek candidate plastid markers that best capture the identity of component species in an eDNA metabarcoding study. We ranked the core plastid genes of 107 published plastid genomes based on various sequence-derived properties and their tree distance to plastid genome phylogenies and found that the most widely used marker, rbcL, is not necessarily the optimal marker, while more informative markers might have been overlooked. We designed and tested PCR primers for several candidate marker genes, and successfully amplified one of these, rpoC1, for a taxonomically broad set of red algal specimens. We suggest that our general marker identification methodology and the rpoC1 primers will be useful to the phycological community for eDNA metabarcoding of the red algae.

opencc-zeroJul 2019View details →

Data from: Non-photosynthetic predators are sister to red algae

Rhodophyta (red algae) is one of three lineages of Archaeplastida, a supergroup that is united by the primary endosymbiotic origin of plastids in eukaryotes. Red algae are a diverse and species-rich group, members of which are typically photoautotrophic, but are united by a number of highly derived characteristics: they have relatively small intron-poor genomes, reduced metabolism and lack cytoskeletal structures that are associated with motility, flagella and centrioles. This suggests that marked gene loss occurred around their origin; however, this is difficult to reconstruct because they differ so much from the other archaeplastid lineages, and the relationships between these lineages are unclear. Here we describe the novel eukaryotic phylum Rhodelphidia and, using phylogenomics, demonstrate that it is a closely related sister to red algae. However, the characteristics of the two Rhodelphis species described here are nearly opposite to those that define red algae: they are non-photosynthetic, flagellate predators with gene-rich genomes, along with a relic genome-lacking primary plastid that probably participates in haem synthesis. Overall, these findings alter our views of the origins of Rhodophyta, and Archaeplastida evolution as a whole, as they indicate that mixotrophic feeding—that is, a combination of predation and phototrophy—persisted well into the evolution of the group.

opennotspecifiedAug 2018View details →

FIGURE 1 in A catalogue and bibliography of non-marine (freshwater and estuarine) Rhodophyta (red algae) of India

FIGURE 1. Map of India showing 29 States and Seven Union Territories.

opencc-zeroJul 2021View details →

Hydrogen peroxide signaling mediates fertilization and post-fertilization development in the red alga Bostrychia moritziana

Reactive oxygen species (ROS) signaling has a multitude of roles in cellular processes throughout biology. We hypothesized that red algal fertilization may offer an interesting model to study ROS-mediated signaling as the stages of fertilization are complex and unique. We microscopically localized ROS production and monitored the expression of three homologues of NADPH-oxidase in reproductive cells during fertilization. ROS were instantaneously produced by spermatia (sperm) when they attached to female trichogynes, diffused across the cell membrane in the form of H2O2, and triggered ROS generation in the carpogonium (egg) as well as carpogonial branch cells which are not in direct contact with spermatia. The expression of NADPH-oxidase homologues, Bmrbohs, began to be upregulated in the female plant upon gamete binding, peaking during the fertilization process and descending back to their original level after fertilization. Pretreatment with diphenylene iodonium (DPI) or caffeine blocked the gene expression as well as H2O2 production. Post-fertilization development was also inhibited when the redox state of the plants were perturbed with H2O2 at any time before or after the fertilization. Our results suggest that H2O2 acts as an auto-propagating signaling molecule, possibly through Ca+2 channel activation, and regulates gene expression involved in fertilization as well as post-fertilization development in red algae. Reactive oxygen species (ROS) signaling has a multitude of roles in cellular processes throughout biology. We hypothesized that red algal fertilization may offer an interesting model to study ROS-mediated signaling as the stages of fertilization are complex and unique. We microscopically localized ROS production and monitored the expression of three homologues of NADPH-oxidase in reproductive cells during fertilization. ROS were instantaneously produced by spermatia (sperm) when they attached to female trichogynes, diffused across the cell membrane in the form of H2O2, and triggered ROS generation in the carpogonium (egg) as well as carpogonial branch cells which are not in direct contact with spermatia. The expression of NADPH-oxidase homologues, Bmrbohs, began to be upregulated in the female plant upon gamete binding, peaking during the fertilization process and descending back to their original level after fertilization. Pretreatment with diphenylene iodonium (DPI) or caffeine blocked the gene expression as well as H2O2 production. Post-fertilization development was also inhibited when the redox state of the plants were perturbed with H2O2 at any time before or after the fertilization. Our results suggest that H2O2 acts as an auto-propagating signaling molecule, possibly through Ca+2 channel activation, and regulates gene expression involved in fertilization as well as post-fertilization development in red algae.

Fig. 3 in Condensation derivatives of 4-isopropylbenzaldehyde with acetophenone from the red alga Laurencia tristicha

Fig. 3. Key NOESY correlations of compounds 3 and 4.

Fig. 5 in Condensation derivatives of 4-isopropylbenzaldehyde with acetophenone from the red alga Laurencia tristicha

Fig. 5. Plausible biosynthetic pathway of compounds 1–5.

Fig. 2 in Condensation derivatives of 4-isopropylbenzaldehyde with acetophenone from the red alga Laurencia tristicha

Fig. 2. Key COSY and HMBC correlations of compounds 1–4.

Fig. 1 in Condensation derivatives of 4-isopropylbenzaldehyde with acetophenone from the red alga Laurencia tristicha

Fig. 1. Structures of compounds 1–6.