Biology subjects

Hauser, D. A.

Publications and source records attributed to Hauser, D. A..

3 recordsLinked to original sources

bioRxiv2021

Monodopsis and Vischeria genomes elucidate the biology of eustigmatophyte algae

Members of eustigmatophyte algae, especially Nannochloropsis, have been tapped for biofuel production owing to their exceptionally high lipid content. While extensive genomic, transcriptomic, and synthetic biology toolkits have been made available for Nannochloropsis, very little is known about other eustigmatophytes. Here we present three near-chromosomal and gapless genome assemblies of Monodopsis (60 Mb) and Vischeria (106 Mb), which are the sister groups to Nannochloropsis. These genomes contain unusually high percentages of simple repeats, ranging from 12% to 21% of the total assembly size. Unlike Nannochloropsis, LINE repeats are abundant in Monodopsis and Vischeria and might constitute the centromeric regions. We found that both mevalonate and non-mevalonate pathways for terpenoid biosynthesis are present in Monodopsis and Vischeria, which is different from Nannochloropsis that has only the latter. Our analysis further revealed extensive spliced leader trans-splicing in Monodopsis and Vischeria at 36-61% of genes. Altogether, the high-quality genomes of Monodopsis and Vischeria not only serve as the much-needed outgroups to advance Nannochloropsis research, but also shed new light on the biology and evolution of eustigmatophyte algae.

genomics↗

bioRxiv2021

Revisiting the early evolution of Cyanobacteria with a new thylakoid-less and deeply diverged isolate from a hornwort

Cyanobacteria have played pivotal roles in Earths geological history especially during the rise of atmospheric oxygen. However, our ability to infer the early transitions in Cyanobacteria evolution has been limited by their extremely lopsided tree of life--the vast majority of extant diversity belongs to Phycobacteria (or "crown Cyanobacteria"), while its sister lineage, Gloeobacteria, is depauperate and contains only two closely related species of Gloeobacter and a metagenome-assembled genome. Here we describe a new culturable member of Gloeobacteria, Anthocerobacter panamensis, isolated from a tropical hornwort. Anthocerobacter diverged from Gloeobacter over 1.4 billion years ago and has low 16S identities with environmental samples. Our ultrastructural, physiological, and genomic analyses revealed that this species possesses a unique combination of traits that are exclusively shared with either Gloeobacteria or Phycobacteria. For example, similar to Gloeobacter, it lacks thylakoids and circadian clock genes, but the carotenoid biosynthesis pathway is typical of Phycobacteria. Furthermore, Anthocerobacter has one of the most reduced gene sets for photosystems and phycobilisomes among Cyanobacteria. Despite this, Anthocerobacter is capable of oxygenic photosynthesis under a wide range of light intensities, albeit with much less efficiency. Given its key phylogenetic position, distinct trait combination, and availability as a culture, Anthocerobacter opens a new window to further illuminate the dawn of oxygenic photosynthesis.

evolutionary biology↗

bioRxiv2020

Symbiotic cyanobacteria communities in hornworts across time, space, and host species

RationaleWhile plant-microbe interactions have been intensively studied in mycorrhizal and rhizobial symbioses, much less is known about plant symbioses with nitrogen-fixing cyanobacteria. Here we focused on hornworts (a bryophyte lineage), and investigated the diversity of their cyanobionts and how these communities are shaped by spatial, temporal, and host factors. MethodWe carried out repeated samplings of hornwort and soil samples in upstate New York throughout the growing season. Three sympatric hornwort species were included, allowing us to directly compare partner specificity and selectivity. To profile cyanobacteria communities, we established a new metabarcoding protocol targeting rbcL-X with PacBio long reads. ResultsHornwort cyanobionts have a high phylogenetic diversity, including clades that do not contain other known plant or lichen symbionts. While the sympatric hornwort species have similarly low specificity, they exhibit different preferences toward cyanobionts, although this depended on what cyanobacteria were present in the soil. Cyanobacterial communities varied spatially, even at small scales, but time did not play a major organizing role. Conclusion.This study highlights the importance of sampling soil and sympatric species to infer partner compatibility and preference, and marks a critical step toward better understanding the ecology and evolution of plant-cyanobacteria symbiosis.

plant biology↗