Cross-kingdom hormonal signaling: an insight from thyroid hormone functions in marine larvae

Abstract

SUMMARY Thyroid hormones (THs) are small, lipophilic signaling molecules built from tyrosine and iodine. TH action is well characterized in vertebrates, where these molecules play a fundamental role as regulators of development,metabolism, growth and differentiation. Increasing evidence suggests that THs also function in a variety of invertebrate species. Two alternative sources of hormone for animals are exogenous (from food items) and endogenous synthesis. We propose that exogenous THs can convey environmental information as well as regulate metabolism, revealing new communication avenues between organisms from different kingdoms. While such modes of cross-kingdom communication have been previously considered for fatty acid-based signaling and steroid hormones in plant–animal interactions, this is the first attempt to explore such a mode of action for TH signaling. We suggest that exogenous sources of TH(from food) may have been ancestral, while the ability to synthesize TH endogenously may have evolved independently in a variety of metazoans,resulting in a diversity of signaling pathways and, possibly, morphological structures involved in TH-signaling.

The evolution of endothermy is explained by thyroid hormone-mediated responses to cold in early vertebrates

“…In contrast to most invertebrates, all chordates and some derived echinoderms and molluscs have evolved the capacity for internal thyroid hormone synthesis using exogenous sources of iodine (Heyland and Moroz, 2005;Heyland et al, 2006;Holzer and Laudet, 2013). This process occurs in the endostyle of nonvertebrate chordates, which is homologous to the thyroid gland in vertebrates (Eales, 1997).…”

“…For example, in feeding echinoderm larvae, thyroid hormone regulates the allocation of energy to larval feeding structures in nutrient-poor conditions, thereby facilitating nutrient uptake. In nutrient-rich environments, however, thyroid hormone directs the allocation of energy to metamorphosis or juvenile structures to promote development (Heyland and Moroz, 2005). In the Pacific sand dollar, Dendraster excentricus, thyroid hormone derived from ingested unicellular marine algae accumulates in the pelagic larvae until a critical concentration threshold signals metamorphic competence ; this process also mediates the transition from a pelagic to a benthic lifestyle.…”

“…However, the precarious supply of thyroid hormone from dietary sources would preclude it from assuming the essential functions it has in vertebrates. For example, the regulation of mammalian thermogenesis by thyroid hormone could not continually maintain body temperature if its availability were tied to the availability of particular food sources.In contrast to most invertebrates, all chordates and some derived echinoderms and molluscs have evolved the capacity for internal thyroid hormone synthesis using exogenous sources of iodine (Heyland and Moroz, 2005;Heyland et al, 2006;Holzer and Laudet, 2013). This process occurs in the endostyle of nonvertebrate chordates, which is homologous to the thyroid gland in vertebrates (Eales, 1997).…”

Iodine accumulation in sea urchin larvae is dependent on peroxide

“…By feeding on algae, sea urchin larvae may receive iodine in a much more concentrated form. Furthermore, if larvae receive TH precursors or the active hormones themselves, these can affect their metabolism during development and metamorphosis (Chino et al, 1994;Heyland, 2004;Heyland and Moroz, 2005;.…”

Effective Detection, Isolation and Characterization of Dakaramine from Ghanaian Axinella sp and Bioactivity

“…The continued isolation of iodotyramine derivatives from different marine organisms offers direct attestation of their importance. These metabolites are known to function as cross-kingdom signalling molecules, regulators of development, growth or differentiation and metabolism [7]. The first iodotyramine derivative to come from marine sources is 2,5-diiodotyrosine, isolated from the octocoral Gorgonia cavolii [8].…”