Biology subjects

Derbyshire, M. C.

Publications and source records attributed to Derbyshire, M. C..

5 recordsLinked to original sources

bioRxiv2026

Pedigree-reconciled pan-genomics reveals megabase-scale hitchhiking after a century of canola breeding

Canola breeding has been shaped by strong selection for oil quality, yet the origins of the known oil quality alleles and genomic consequences of their selection are not fully resolved. By integrating pedigree reconstruction with graph pan-genomics we trace inheritance of ancestral genomic regions across historical and contemporary germplasm. Surrounding the low erucic acid allele in BnA08.FAE1, we identify a 17.23 Mb haplotype that approached fixation in Australian canola in the early 2000s. Contradicting the prevailing model, this haplotype predates modern breeding and was likely widespread in ancestral B. napus in the early 1900s. Genomic analyses implicate centromeric recombination suppression and structural variation in its long-term persistence, which has led to megabase-scale diversity loss through hitchhiking of neighbouring alleles. The haplotype contains extensive structural variation and multiple alleles associated with polygenic disease resistance. Together, these findings reveal the long-term consequences of repeated selection on standing variation during crop improvement.

plant biology↗

bioRxiv2024

Cryptic recombination and transposition drive structural variation to shape genomic plasticity and life history traits in a host generalist fungal plant pathogen

BackgroundAn understanding of plant pathogen evolution is important for sustainable management of crop diseases. Plant pathogen populations must maintain adequate heritable phenotypic variability to survive. Polymorphisms >= 50 bp, known as structural variants (SVs), could contribute strongly to this variability by disrupting gene activities. SV acquisition is largely driven by mobile genetic elements called transposons, though a less appreciated source of SVs is erroneous meiotic double-strand break repair. The relative impacts of transposons and recombination on SV diversity and the overall contribution of SVs to phenotypic variability is elusive, especially in host generalists. ResultsWe use 25 high quality genomes to create a graphical pan-genome of the globally distributed host-generalist crop pathogen Sclerotinia sclerotiorum. Outcrossing and recombination rates in this self-fertile species have been debated. Using bisulfite sequencing, and short read data from 190 strains, we show that S. sclerotiorum has many hallmarks of eukaryotic meiosis, including recombination hot and cold spots, centromeric and genic recombination suppression, and rapid linkage disequilibrium decay. Using a new statistic that captures average pairwise structural variation, we show that recombination and transposons make distinct contributions to SV diversity. Furthermore, despite only 5 % of genes being dispensable, SVs often had a stronger impact than other variants across 14 life history traits measured in 103 distinct strains. ConclusionTransposons and recombination make distinct contributions to SV diversity in S. sclerotiorum. Despite limited gene content diversity, SVs may strongly impact phenotypic variability. This sheds light on the genomic forces shaping adaptive flexibility in host generalists.

genomics↗

bioRxiv2023

Surface frustration re-patterning underlies the structural landscape and evolvability of fungal orphan candidate effectors

Pathogens secrete effector proteins to subvert host physiology and cause disease. Effectors are engaged in a molecular arms race with the host resulting in conflicting evolutionary constraints to manipulate host cells without triggering immune responses. The molecular mechanisms allowing effectors to be at the same time robust and evolvable remain largely enigmatic. Here, we show that 62 conserved structure-related families encompass the majority of fungal orphan effector candidates at the subphylum level. These effectors diversified through changes in patterns of thermodynamic frustration at surface residues. The underlying mutations tended to increase the robustness of the overall effector protein structure while switching potential binding interfaces. This mechanism could explain how conserved effector families maintained biological activity over long evolutionary timespans in different host environments and provides a model for the emergence of sequence-unrelated effector families with conserved structures.

genomics↗

bioRxiv2020

Combined degradome and replicated small RNA sequencing identifies Brassica napus small RNAs responsive to infection by a necrotrophic pathogen

BackgroundSmall RNAs are short non-coding RNAs that are key gene regulators controlling various biological processes in eukaryotes. Plants may regulate discrete sets of sRNAs in response to pathogen attack. Sclerotinia sclerotiorum is an economically important pathogen affecting hundreds of plant species, including the economically important oilseed Brassica napus. However, there are limited studies on how regulation of sRNAs occurs in the S. sclerotiorum and B. napus pathosystem. ResultsWe identified different classes of sRNAs from B. napus by high throughput sequencing of replicated mock and infected samples at 24 hours post-inoculation (HPI). Overall, 3,999 sRNA loci were highly expressed, of which 730 were significantly upregulated during infection. Degradome sequencing identified numerous likely sRNA targets that were enriched for immunity-related GO terms, including those related to jasmonic acid signalling, during infection. A total of 73 conserved miRNA families were identified in our dataset. Degradome sequencing identified 434 unique cleaved mRNA products from these miRNAs, of which 50 were unique to the infected library. A novel miR1885-triggered disease resistance gene-derived secondary sRNA locus was identified and verified with degradome sequencing. We also experimentally validated silencing of a plant immunity related ethylene response factor gene by a novel sRNA using 5-RACE. ConclusionsThe findings in this study expand the framework for understanding the molecular mechanisms of the S. sclerotiorum and B. napus pathosystem at the sRNA level.

molecular biology↗

bioRxiv2018

Small RNAs from the plant pathogenic fungus Sclerotinia sclerotiorum highlight candidate host target genes associated with quantitative disease resistance

Plant pathogenic fungi secrete effector proteins and secondary metabolites to cause disease. Additionally, some produce small RNAs (sRNAs) that silence transcripts of host immunity genes through RNA interference. The fungus Sclerotinia sclerotiorum infects over 600 plant species, but little is known about its molecular interactions with its hosts. In particular, the role of sRNAs in S. sclerotiorum pathogenicity has not been determined. By sequencing sRNAs in vitro and during infection of two host species, we found that S. sclerotiorum produces at least 374 highly abundant sRNAs. These sRNAs mostly originated from polymorphic repeat-rich genomic regions. Predicted gene targets of these sRNAs, from 10 different host species, were enriched for immunity-related functional domains. Predicted A. thaliana gene targets of S. sclerotiorum sRNAs were significantly more down-regulated during infection than other genes. A. thaliana gene targets were also more likely to contain single nucleotide polymorphisms (SNPs) associated with quantitative disease resistance. In conclusion, sRNAs produced by S. sclerotiorum are likely capable of silencing immunity components in multiple hosts. Prediction of fungal sRNA targets in host plant genomes can be combined with other global approaches, such as genome wide association studies and transcriptomics, to assist identification of plant genes involved in disease resistance.

plant biology↗