Immunolocalization of the Toxin Latrunculin B within the Red Sea Sponge Negombata magnifica (Demospongiae, Latrunculiidae)

Abstract

The location of latrunculin B, the major toxin of the Red Sea sponge Negombata magnifica, was revealed using specific antibodies. Antibodies from rabbits immunized with a conjugate of latrunculin B with keyhole limpet hemocyanin (KLH) were purified over a latrunculin B-Sepharose affinity column. Analysis of immunohistochemical and immunogold-stained sponge sections, using light and transmission electron microscopy, revealed latrunculin B labeling mostly beneath the sponge cortex at the border between the external (ectosome) and internal (endosome) layers (ectosome-endosome border). The endosome was less labeled than the border. Immunogold localization revealed latrunculin B in the sponge cells but not in its prokaryotic symbionts. Archeocytes and choanocytes were significantly more labeled than other cells. The antibodies primarily labeled membrane-limited vacuoles within archeocytes and choanocytes that are perhaps latrunculin B secretory or storage vesicles. Peripheral latrunculin B may have a role in defense against external epibionts, predators, and competitors.

Chemical Defenses: From Compounds to Communities

“…Through Ficoll density-gradient fractionation and centrifugation, sponge cells were separated from their associated bacteria, and isocyano terpenes were localized to sponge cell membranes in Amphimedon terpenensis (Garson et al, 1992). Though bioactive compounds have been localized on the cellular level in several sponges (Unson et al, 1994;Flowers et al, 1998;Gillor et al, 2000;Salomon et al, 2001), localization may simply indicate the site where a compound is needed, rather than the site of origin (reviewed in Hildebrand et al, 2004b;and König et al, 2006). Molecular biology and metagenomics techniques based on identification of biosynthetic gene clusters have laid a foundation for future work to determine the source of bioactive compounds in many marine invertebrates (Davidson et al, 2001;Piel et al, 2004Piel et al, , 2005Flatt et al, 2005;Schmidt, 2005;Schmidt et al, 2005).…”

Particulate organic matter as a food source for a coral reef sponge

“…This branching sponge lives (at 3-60m depth) either exposed or inside caves (Ilan, 1995). It seldom exhibits photosynthetic activity (E.H., unpublished data), and is virtually microsymbiont-free (bacteria were seldom observed in histological sections) (Gillor et al, 2000).…”

Localization of ‘Candidatus Endobugula sertula’ and the bryostatins throughout the life cycle of the bryozoan Bugula neritina

“…Although several studies have successfully used visualization techniques to localize natural products in situ in various marine invertebrates (Gillor et al, 2000;Salomon et al, 2001;Schroder et al, 2006), the methods used in those studies are not feasible for use in bryostatin localization. In order to detect bryostatins in situ, we developed a method based on their clinical molecular target, mammalian protein kinase C (PKC).…”