Biology subjects

Harry, N. D.

Publications and source records attributed to Harry, N. D..

4 recordsLinked to original sources

bioRxiv2023

Comparative Hox genes expression within the dimorphic annelidStreblospio benedicti reveals patterning variation during development

Hox genes are transcriptional regulators that elicit cell positional identity along the anterior-posterior region of the body plan across different lineages of Metazoan. Comparison of Hox gene expression across distinct species reveals their evolutionary conservation, however their gains and losses in different lineages can correlate with body plan modifications and morphological novelty. We compare the expression of eleven Hox genes found within Streblospio benedicti, a marine annelid that produces two types of offspring with distinct developmental and morphological features. For these two distinct larval types, we compare Hox gene expression through ontogeny using HCR (hybridization chain reaction) probes for in-situ hybridization and RNA-seq data. We find that Hox gene expression patterning for both types is typically similar at equivalent developmental stages. However, some Hox genes have spatial or temporal differences between the larval types that are associated with morphological and life-history differences. This is the first comparison of developmental divergence in Hox genes expression within a single species and these changes reveal how body plan differences may arise in larval evolution.

developmental biology↗

bioRxiv2023

The role of heterochronic gene expression and regulatory architecture in early developmental divergence

New developmental programs can evolve through adaptive changes to gene expression. The annelid Streblospio benedicti has a developmental dimorphism, which provides a unique intraspecific framework for understanding the earliest genetic changes that take place during developmental divergence. Using comparative RNAseq through ontogeny, we find that only a small proportion of genes are differentially expressed at any time, despite major differences in larval development and life-history. These genes shift expression profiles across morphs by either turning off any expression in one morph or changing the timing or amount of gene expression. We directly connect the contributions of these mechanisms to differences in developmental processes. We examine F1 offspring-- using reciprocal crosses-- to determine maternal mRNA inheritance and the regulatory architecture of gene expression. These results highlight the importance of both novel gene expression and heterochronic shifts in developmental evolution, as well as the trans-acting regulatory factors in initiating divergence.

genetics↗

bioRxiv2022

Maternal patterns of inheritance alter transcript expression in eggs

Modifications to early development can lead to evolutionary diversification. The early stages of development are under maternal control, as mothers produce eggs loaded with nutrients, proteins and mRNAs that direct early embryogenesis. Maternally provided mRNAs are the only expressed genes in initial stages of development and are known to be tightly regulated. Differences in maternal mRNA provisioning could lead to phenotypic changes in embryogenesis and ultimately evolutionary changes in development. However, the extent to which variation in maternal mRNA provisioning impacts ontogeny or life-history is unknown. Here, we use a species with dimorphic development-- where females make eggs and larvae of different sizes and life-history modes--to investigate the extent of variation in maternal mRNA provisioning to the egg. We examine the effect of gene expression differences on subsequent generations of egg provisioning and determine the regulatory architecture underlying mRNA provisioning differences. We find that there is significant variation in gene expression across eggs of different development modes, and that both parent-of-origin and allele-specific effects contribute to mRNA expression differences. We also find that offspring of intraspecific crosses differentially provision their eggs based on their parents cross direction. This effect of allelic expression based on parent-of-origin has not been previously demonstrated in reproductive traits like oogenesis. AUTHOR SUMMARYVariation in early developmental programs can provide the basis for evolutionary diversification. In the early embryo, cellular functions are carried out by proteins and transcripts contributed by the mother to the egg until the embryos own genome can take over. Since these maternal factors are responsible for setting up all of the subsequent development of the offspring, they tend to be tightly regulated. However, variation exists in the amount and types of transcripts mothers provide. Here we examine how the variation in maternal transcripts that occurs in eggs of the species Streblospio benedicti, leads to developmental differences. S. benedicti offspring follow one of two distinct developmental programs that originate with egg size differences. We find significant variation in maternally provided transcripts correlated with the two life-histories, and that some of this variation in egg transcripts is directly related to the developmental type of the mothers own parents. This parental effect on how mothers provide transcripts to their eggs has not previously been described and indicates the possibility for an offsprings grandparents to affect their early developmental program by modulating the transcripts their mother provides.

genetics↗

bioRxiv2021

The genome of the poecilogonous annelid Streblospio benedicti

Streblospio benedicti is a common marine annelid that has become an important model for developmental evolution. It is the only known example of poecilogony, where two distinct developmental modes occur within a single species, that is due to a heritable difference in egg size. The dimorphic developmental programs and life-histories exhibited in this species depend on differences within the genome, making it an optimal model for understanding the genomic basis of developmental divergence. Studies using S. benedicti have begun to uncover the genetic and genomic principles that underlie developmental uncoupling, but until now they have been limited by the lack of availability of genomic tools. Here we present an annotated chromosomal-level genome assembly of S. benedicti generated from a combination of Illumina reads, Nanopore long reads, Chicago and Hi-C chromatin interaction sequencing, and a genetic map from experimental crosses. At 701.4 Mb, the S. benedicti genome is the largest annelid genome to date that has been assembled to chromosomal scaffolds, yet it does not show evidence of extensive gene family expansion, but rather longer intergenic regions. The complete genome of S. benedicti is valuable for functional genomic analyses of development and evolution, as well as phylogenetic comparison within the Annelida and the Lophotrochozoa. Despite having two developmental modes, there is no evidence of genome duplication or substantial gene number expansions. Instead, lineage specific repeats account for much of the expansion of this genome compared to other annelids.

genomics↗