Biology subjects

Pauchet, Y.

Publications and source records attributed to Pauchet, Y..

5 recordsLinked to original sources

bioRxiv2023

Paleocene origin of a streamlined digestive symbiosis in leaf beetles

Timing the acquisition of a beneficial microbe relative to the evolutionary history of its host can shed light on the adaptive impact of a partnership. Here, we investigated the onset and molecular evolution of an obligate symbiosis between Cassidinae leaf beetles and Candidatus Stammera capleta, a {gamma}-proteobacterium. Residing extracellularly within foregut symbiotic organs, Stammera upgrades the digestive physiology of its host by supplementing plant cell wall-degrading enzymes. We observe that Stammera is a shared symbiont across tortoise and hispine beetles that collectively comprise the Cassidinae subfamily, despite differences in their folivorous habits. In contrast to its transcriptional profile during vertical transmission, Stammera elevates the expression of genes encoding digestive enzymes while in the foregut symbiotic organs, matching the nutritional requirements of its host. Symbiont acquisition during the Paleocene ([~]62 Mya) did not coincide with the origin of Cassidinae beetles, despite the widespread distribution of Stammera across the subfamily. Early-diverging lineages lack the symbiont and the specialized organs that house it. Reconstructing the ancestral state of host-beneficial factors revealed that Stammera encoded three digestive enzymes at the onset of symbiosis, including polygalacturonase - a pectinase that is universally shared. While non-symbiotic cassidines encode polygalacturonase endogenously, their repertoire of plant cell wall-degrading enzymes is more limited compared to symbiotic beetles supplemented with digestive enzymes from Stammera. Highlighting the potential impact of a symbiotic condition and an upgraded metabolic potential, Stammera-harboring beetles exploit a greater variety of plants and are more speciose compared to non-symbiotic members of the Cassidinae.

evolutionary biology↗

bioRxiv2019

A cytochrome P450 from juvenile mustard leaf beetles hydroxylates geraniol, a key step in iridoid biosynthesis

Juveniles of the leaf beetle Phaedon cochleariae synthesize iridoid via the mevalonate pathway to repel predators. The normal terpenoid biosynthesis is integrated into the dedicated defensive pathway by the {omega}-hydroxylation of geraniol to 8-hydroxygeraniol. Here we identify and characterize the geraniol 8-hydroxylase as a P450 monooxygenase using integrated transcriptomic and proteomic analyses. In the fat body, 73 individual cytochrome P450s were identified. The double stranded RNA (dsRNA)-mediated knock down of CYP6BH5 led to a significant reduction of 8-hydroxygeraniol-glucoside in the hemolymph and, later, of the chrysomelidial in the defensive secretion. Heterologously expressed CYP6BH5 converted geraniol to 8-hydroxygeraniol. In addition to geraniol, CYP6BH5 also catalyzes other monoterpenols, such as nerol and citronellol, into the corresponding , {omega}-dihydroxy compounds.\n\nHighlightsO_LIThe geraniol 8-hydroxylase in Phaedon cochleariae was identified as a cytochrome P450 CYP6BH5.\nC_LIO_LIRNA interference emphasized the importance of CYP6BH5 in iridoid biosynthesis.\nC_LIO_LIIn vitro enzyme assays showed that recombinant CYP6BH5 is a substrate promiscuous enzyme, converting the {omega}-hydroxylation of geraniol, nerol, citronellol but not linalool.\nC_LIO_LIHomology modeling suggested the -OH group of the substrate plays an important role in coordinating the substrates with the enzymes catalytic cavity.\nC_LI

biochemistry↗

bioRxiv2018

Functional analyses of the horizontally acquired Phytophaga glycoside hydrolase family 45 (GH45) proteins reveal distinct functional characteristics

Cellulose, a major polysaccharide of the plant cell wall, consists of {beta}-1,4-linked glucose moieties forming a molecular network recalcitrant to enzymatic breakdown. Although cellulose is potentially a rich source of energy, the ability to degrade it is rare in animals and was believed to be present only in cellulolytic microbes. Recently, it has become clear that some animals encode endogenous cellulases belonging to several glycoside hydrolase families (GHs), including GH45. GH45s are distributed patchily among the Metazoa and, in insects, are encoded only by the genomes of Phytophaga beetles. This study aims to understand both the enzymatic properties and the evolutionary history of GH45s in these beetles. To this end, we tested the enzymatic abilities of 37 GH45s derived from five species of Phytophaga beetles and learned that beetle-derived GH45s degrade three different substrates: amorphous cellulose, xyloglucan and glucomannan. Our phylogenetic and gene structure analyses indicate that at least one gene encoding a putative cellulolytic GH45 was present in the last common ancestor of the Phytophaga, and that GH45 xyloglucanases evolved several times independently in these beetles. The most closely related clade to Phytophaga GH45s contained fungal sequences, suggesting this GH family was acquired by horizontal gene transfer from fungi. Other than in insects, arthropod GH45s do not share a common origin and appear to have emerged at least three times independently.

molecular biology↗

bioRxiv2018

Pectin digestion in herbivorous beetles: Impact of pseudoenzymes exceeds that of their active counterparts

Many protein families harbor pseudoenzymes that have lost the catalytic function of their enzymatically active counterparts. Assigning alternative function and importance to these proteins is challenging [1]. Because the evolution towards pseudoenzymes is driven by gene duplication, they often accumulate in multigene families. Plant cell wall-degrading enzymes (PCWDEs) are prominent examples of expanded gene families. The pectolytic glycoside hydrolase family 28 (GH28) allows herbivorous insects to break down the PCW polysaccharide pectin. GH28 in the Phytophaga clade of beetles contains many active enzymes but also many inactive counterparts. Using functional characterization, gene silencing, global transcriptome analyses and recordings of life history traits, we found that not only catalytically active but also inactive GH28 proteins are part of the same pectin-digesting pathway. The robustness and plasticity of this pathway and thus its importance for the beetle is supported by extremely high steady-state expression levels and counter-regulatory mechanisms. Unexpectedly, the impact of pseudoenzymes on the pectin-digesting pathway in Phytophaga beetles exceeds even the influence of their active counterparts, such as a lowered efficiency of food-to-energy conversion and a prolongation of the developmental period.

physiology↗

bioRxiv2017

A model species for agricultural pest genomics: the genome of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

The Colorado potato beetle is one of the most challenging agricultural pests to manage. It has shown a spectacular ability to adapt to a variety of solanaceaeous plants and variable climates during its global invasion, and, notably, to rapidly evolve insecticide resistance. To examine evidence of rapid evolutionary change, and to understand the genetic basis of herbivory and insecticide resistance, we tested for structural and functional genomic changes relative to other arthropod species using genome sequencing, transcriptomics, and community annotation. Two factors that might facilitate rapid evolutionary change include transposable elements, which comprise at least 17% of the genome and are rapidly evolving compared to other Coleoptera, and high levels of nucleotide diversity in rapidly growing pest populations. Adaptations to plant feeding are evident in gene expansions and differential expression of digestive enzymes in gut tissues, as well as expansions of gustatory receptors for bitter tasting. Surprisingly, the suite of genes involved in insecticide resistance is similar to other beetles. Finally, duplications in the RNAi pathway might explain why Leptinotarsa decemlineata has high sensitivity to dsRNA. The L. decemlineata genome provides opportunities to investigate a broad range of phenotypes and to develop sustainable methods to control this widely successful pest.

genomics↗