Evolution and Diversity of TGF-β Pathways are Linked with Novel Developmental and Behavioral Traits

Abstract

Transforming growth factor β (TGF-β) signalling is essential for numerous biological functions. It is a highly conserved pathway found in all metazoans including the nematode Caenorhabditis elegans, which has also been pivotal in identifying many components. Utilising a comparative evolutionary approach, we explored TGF-β signalling in nine nematode species and revealed striking variability in TGF-β gene frequency across the lineage. Of the species analysed, gene duplications in the DAF-7 pathway appear common with the greatest disparity observed in Pristionchus pacificus. Specifically, multiple paralogues of daf-3, daf-4 and daf-7 were detected. To investigate this additional diversity, we induced mutations in 22 TGF-β components and generated corresponding double, triple and quadruple mutants revealing both conservation and diversification in function. Although, the DBL-1 pathway regulating body morphology appears highly conserved, the DAF-7 pathway exhibits functional divergence, notably in some aspects of dauer formation. Furthermore, the formation of the phenotypically plastic mouth in P. pacificus is partially influenced through TGF-β with the strongest effect in Ppa-tag-68. This appears important for numerous processes in P. pacificus but has no known function in C. elegans. Finally, we observe behavioural differences in TGF-β mutants including in chemosensation and the establishment of the P. pacificus kin-recognition signal. Thus, TGF-β signalling in nematodes represents a stochastic genetic network capable of generating novel functions through the duplication and deletion of associated genes.

A histone demethylase links the loss of plasticity to nongenetic inheritance and morphological change

“…Previously, all described regulators and effectors of the Pristionchus mouth polyphenism had reported influence on just one axis of variation. Whereas some affect the ratio under which a stereotypical morph is produced, through effects on either sensory perception or endogenous signalling 16 , 17 , 51 , 52 , mutations in others cause morph-constitutive phenotypes that assume aberrant but nevertheless consistent forms 15 , 53 . Presumably through its genome-wide effects as a chromatin modifier, spr-5 shows mutant phenotypes both in plasticity and in morphological trait values.…”

Microbiota Succession Influences Nematode Physiology in a Beetle Microcosm Ecosystem

“…However, P. pacificus has a wider range of temperature tolerance (Leaver et al 2022) and different strains display varying capacities of inducing dauer larvae through pheromones produced by their own genotype (Mayer and Sommer 2011). Recent genetic studies indicated that TGF-β signalling pathway, which regulates dauer formation in C. elegans, may not play the major role in P. pacificus (Lo, Roca, et al 2022). Deficiency in the vitamin B family and the presence of a pathogen may act as cues for P. pacificus to enter the dauer stage through the signal transduction of the mTOR pathway.…”

cGMP-dependent pathway and a GPCR kinase are required for photoresponse in the nematodePristionchus pacificus

“…The diplogastrid nematode Pristionchus pacificus has been established as a satellite model organism for comparison with C. elegans [21][22][23]. Several genetic tools have been developed for P. pacificus, such as an annotated genome [24,25], forward and reverse genetics [21,26], and synaptic connectome in pharynx and amphid neurons revealed using electron microscope [27,28], which provide a suitable model to understand its neural response and behavioral evolution [29][30][31][32][33][34][35][36][37][38]. Both C. elegans and P. pacificus have 12 pairs of amphid neurons, and putative amphid neuronal homologs have been identified between these two species [27].…”