Unexpected Distribution of Chitin and Chitin Synthase across Soft-Bodied Cnidarians

Abstract

Cnidarians are commonly recognized as sea jellies, corals, or complex colonies such as the Portuguese man-of-war. While some cnidarians possess rigid internal calcareous skeletons (e.g., corals), many are soft-bodied. Intriguingly, genes coding for the chitin-biosynthetic enzyme, chitin synthase (CHS), were recently identified in the model anemone Nematostella vectensis, a species lacking hard structures. Here we report the prevalence and diversity of CHS across Cnidaria and show that cnidarian chitin synthase genes display diverse protein domain organizations. We found that CHS is expressed in cnidarian species and/or developmental stages with no reported chitinous or rigid morphological structures. Chitin affinity histochemistry indicates that chitin is present in soft tissues of some scyphozoan and hydrozoan medusae. To further elucidate the biology of chitin in cnidarian soft tissues, we focused on CHS expression in N. vectensis. Spatial expression data show that three CHS orthologs are differentially expressed in Nematostella embryos and larvae during development, suggesting that chitin has an integral role in the biology of this species. Understanding how a non-bilaterian lineage such as Cnidaria employs chitin may provide new insight into hitherto unknown functions of polysaccharides in animals, as well as their role in the evolution of biological novelty.

Morphological and dietary changes encoded in the genome of Beroe ovata, a ctenophore-eating ctenophore

“…Most animals can synthesize chitin ( 95 ), but chitin synthase is not present in the Mnemiopsis genome ( 96 ), and based on phylogenetic analyses ( 97 ), as well as biophysical characteristics, ctenophores are not thought to be able to produce chitin ( 98 ). However, the use of highly sensitive proteomic analyses is needed to confirm the absence of chitin in ctenophores.…”

Sequential host-bacteria and bacteria-bacteria interactions determine the microbiome establishment of Nematostella vectensis

“…Although it has already been known for several years that Nematostella possesses at least two genes for chitin synthesis [57], there is just emerging evidence that soft-bodied anemones also express chitin synthase genes [58]. The expression strength indicates a mechanism where chitin is continuously produced while bacteria are present but its production halts if bacteria are missing (Fig.…”

“…In addition, micro-particles of chitin have been shown to enable the community assembly of free-living seawater bacteria [61]. A variety of early-branching metazoans express chitin synthases but it is unknown what function they express [57,58]. In the context of host-microbiome associations, host-produced chitin is known to modulate the immune response [62].…”

Marine Bioprospecting: Enzymes and Stress Proteins from the Sea Anemones Anthopleura dowii and Lebrunia neglecta

“…While sea anemones have long been recognized as rich sources of polypeptides with various pharmacological activities, it was not until a few years ago that proteomic and transcriptomic methods were implemented to explore the proteins in their secretions and tissues [29,31,32]. Bioprospecting in these venomous marine invertebrates has traditionally focused on polypeptides with neurotoxic [33,34] and cytotoxic properties [35], with little attention given to other components of biotechnological interest, such as enzymes, amylases [36], chitinases [37], proteases [29,31], oxidoreductases [38,39], heat shock proteins [40], and structural proteins [41], which have been identified in their crude venom extracts (CVEs) and secretions. These enzymes can potentially be used to develop tools for medical and industrial applications [42,43].…”