Biology subjects

Dunker, F.

Publications and source records attributed to Dunker, F..

5 recordsLinked to original sources

bioRxiv2026

Growth, survival, and fitness in the first year of life for Pycnopodia helianthoides under different larval densities

Sea star wasting disease has caused widespread mortality in the kelp forest predator, the sunflower sea star (Pycnopodia helianthoides). Wild populations have declined by up to 99% in parts of their native range along the western North American coast. In response, a multi-institutional conservation breeding and rearing program has been initiated to support future reintroduction efforts for the species. We split a full-sibling cohort across four larval density treatments (1 larva/ml, 2 larvae/ml, 5 larvae/ml, and 15-20 larvae/ml) to assess the effects on larval settlement, juvenile survival, and juvenile fitness at 12 months old. Stars raised in the highest density treatment displayed a lower settlement rate and were significantly smaller than the other density groups at 12 months old, but showed no significant difference in flip time, a measure of fitness. Additionally, measurements of diameter, weight, and arm count across modern and historical juvenile and adult stars indicate that P. helianthoides experience exponential weight gain as they grow in length, with corresponding asymptotic growth in arm count. These findings will inform best practices for the aquarium propagation of P. helianthoides and will contribute to broader efforts aimed at reestablishing populations in the wild.

developmental biology↗

bioRxiv2023

A fungal RNA-dependent RNA polymerase is a novel player in plant infection and cross-kingdom RNA interference

Small RNAs act as fungal pathogen effectors that silence host target genes to promote infection, a virulence mechanism termed cross-kingdom RNA interference (RNAi). The essential pathogen factors of cross-kingdom small RNA production are largely unknown. We here characterized the RNA-dependent RNA polymerase (RDR)1 in the fungal plant pathogen Botrytis cinerea that is required for pathogenicity and cross-kingdom RNAi. B. cinerea bcrdr1 knockout (ko) mutants exhibited reduced pathogenicity and loss of cross-kingdom small RNAs. We developed a novel "switch-on" GFP reporter to study cross-kingdom RNAi in real-time within the living plant tissue which highlighted that bcrdr1 ko mutants were compromised in cross-kingdom RNAi. Moreover, blocking seven pathogen cross-kingdom small RNAs by expressing a short-tandem target mimic RNA in transgenic Arabidopsis thaliana led to reduced infection levels of the fungal pathogen B. cinerea and the oomycete pathogen Hyaloperonospora arabidopsidis. These results demonstrate that cross-kingdom RNAi is significant to promote host infection and making pathogen small RNAs an effective target for crop protection.

pathology↗

bioRxiv2023

Commensal protists in reptiles display flexible host range and adaptation to ectothermic hosts

Parabasalid protists recently emerged as keystone members of the mammalian microbiota with important effects on their hosts health. However, the prevalence and diversity of parabasalids in wild reptiles and the consequences of captivity and other environmental factors on these symbiotic protists are unknown. Reptiles are ectothermic, and their microbiomes are subject to temperature fluctuations, such as those driven by climate change. Thus, conservation efforts for threatened reptile species may benefit from understanding how shifts in temperature and captive breeding influence the microbiota, including parabasalids, to impact host fitness and disease susceptibility. Here, we surveyed intestinal parabasalids in a cohort of wild reptiles across three continents and compared these to captive animals. Reptiles harbor surprisingly few species of parabasalids compared to mammals, but these protists exhibited a flexible host-range, suggesting specific adaptations to reptilian social structures and microbiota transmission. Furthermore, reptile-associated parabasalids are adapted to wide temperature ranges, although colder temperatures significantly altered the protist transcriptomes, with increased expression of genes associated with detrimental interactions with the host. Our findings establish that parabasalids are widely distributed in the microbiota of wild and captive reptiles and highlight how these protists respond to temperature swings encountered in their ectothermic hosts.

microbiology↗

bioRxiv2022

Kinship and genetic variation in aquarium-spawned Acropora hyacinthus corals

Recent scientific advances in ex situ system design and operation make it possible to complete gametogenic cycles of broadcast spawning corals. Breeding corals in aquaria are critical advances for population management, particularly genetic rescue and assisted gene flow efforts. Genetic rescue projects for corals are already underway to bring threatened species into ex situ culture and propagation, thereby preserving standing genetic variation. However, while breeding corals is increasingly feasible, the consequences of the aquarium environment on the genetic and phenotypic composition of coral populations is not yet known. The aquarium environment may in itself be a selective pressure on corals, but it also presents relaxed selective pressure in other respects. In 2019 and 2020, gravid Acropora hyacinthus coral colonies were collected from Palauan reefs and shipped to the California Academy of Sciences (CAS) in San Francisco. In both years, gametes were batch-fertilized to produce larvae that were then settled and reared to recruits. As of April 2021, when they were sampled for sequencing, 23 corals produced at CAS in 2019 and 16 corals produced at CAS in 2020 had survived for two years and one year, respectively. We sequenced the full genomes of the 39 offspring corals and their 15 potential parents to a median 26x depth of coverage. We find clear differential parentage, with some parents producing the vast majority of offspring, while the majority of parents produced no surviving offspring. After scanning 12.9 million single nucleotide polymorphisms (SNPs), we found 887 SNPs that may be under selection in the aquarium environment, and we identified the genes and pathways these SNPs may affect. We present recommendations for preserving standing genetic variation in aquarium-bred corals based on the results of this pilot project.

evolutionary biology↗

bioRxiv2019

Oomycete small RNAs invade the plant RNA-induced silencing complex for virulence

Fungal small RNAs (sRNAs) hijack the plant RNA silencing pathway to manipulate host gene expression, named cross-kingdom RNA interference (ckRNAi). It is currently unknown how conserved and significant ckRNAi is for microbial virulence. Here, we found for the first time that sRNAs of a pathogen representing the oomycete kingdom invade the host plants Argonaute (AGO)/RNA-induced silencing complex. To demonstrate the functionality of the plant-invading oomycete Hyaloperonospora arabidopsidis sRNAs (HpasRNAs), we designed a novel CRISPR endoribonuclease Csy4/GUS repressor reporter to visualize in situ pathogen-induced target suppression in Arabidopsis thaliana host plant. By using 5 RACE-PCR we demonstrated HpasRNAs-directed cleavage of plant mRNAs. The significant role of HpasRNAs together with AtAGO1 in virulence was demonstrated by plant atago1 mutants and by transgenic Arabidopsis expressing a target mimic to block HpasRNAs, that both exhibited enhanced resistance. Individual HpasRNA plant targets contributed to host immunity, as Arabidopsis gene knockout or HpasRNA-resistant gene versions exhibited quantitative enhanced or reduced susceptibility, respectively. Together with previous reports, we found that ckRNAi is conserved among oomycete and fungal pathogens.

microbiology↗