Petek, S. | bioRxiv Science

bioRxiv2024

Barcoding-inferred biodiversity of shallow-water Indo-Pacific demosponges

AimThe Indo-Pacific is the worlds largest marine biogeographic region. It is characterised by different degrees of connectivity among its subregions, and harbours the majority of demosponge species currently known to science. Comparisons between several regional sponge faunas have been undertaken in the past, mostly based on identifying the sponge species morphologically. The Sponge Barcoding Project, in tandem with other regional DNA taxonomy campaigns, provides one of the largest DNA-based taxonomic data collections from sponges of the Indo-Pacific. Here, we utilise the sponge barcoding data in the largest molecular biodiversity study of sponges to date, which reveals patterns of shallow-water demosponge faunal connectivity, endemism, and distribution in the Indo-Pacific with a level of resolution unavailable in prior morphology-based studies. LocationDemosponge specimens in this study cover 13 marine provinces of the Indo-Pacific, from the Red Sea to South East Polynesia. MethodsWe classified demosponge barcodes using the ribosomal subunit (28S rDNA) of 1,910 sponge samples into molecular operational taxonomic units (MOTUs). MOTU composition of the 13 marine provinces was compared based on Jaccard and Sorenson dissimilarities, and other biodiversity indices. ResultsOur data corroborated high levels of endemism among demosponges. Faunal overlaps were revealed between the Red Sea and the Gulf, which displayed relatively small connectivity with other marine provinces of the Western Indian Ocean. In the Western Indian Ocean, we observed a strong faunistic boundary to the Central Indo-Pacific. The Polynesian sponge faunas were comparatively isolated marine provinces of the Central Indo-Pacific. Main conclusionsOur data corroborate case studies on sponges that generally reject the presence of cosmopolitan or otherwise widespread sponge species, instead revealing high levels of regional endemism. This is consistent with similar observations and hypotheses in other marine invertebrates. Connectivity among Indo-Pacific marine provinces differs for demosponges in many aspects from that of other marine taxa, such as corals and fishes, probably due to their shorter pelagic larval phase.

zoology↗

bioRxiv2023

Sterols from cholesterol synthesis control distinct gene regulatory pathways

Sterol intermediates of cholesterol synthesis are largely dedicated to cholesterol. Here we assess how they influence downstream gene regulatory pathways by developing knockouts (KOs) for consecutive enzymes of cholesterol synthesis in human hepatoma HepG2 cells. The KO of CYP51, DHCR24, and SC5D led to the build-up of specific sterols. The shared differentially expressed genes accounted for only 9% with regards to steroid metabolism and proliferation control, with majority of pathways changed in just one KO. The CYP51 KO cells with highly elevated 24,25-dihydrolanosterol exhibited a significant increase in G2+M phase along with enhanced cancer and cell cycle pathways, likely driven by elevated LEF1 through modulation of WNT/NFKB signalling. In contrast, SC5D and DHCR24 KO cells with elevated lathosterol or desmosterol, slowed cell proliferation and promoted apoptosis with downregulated E2F, mitosis, cell cycle transition, and enriched HNF1A tumor suppressor. These findings demonstrate that sterols from cholesterol synthesis control distinct gene regulatory pathways, while only early sterols can promote cell proliferation.

biochemistry↗