title: Mevalonosomes: specific vacuoles containing the mevalonate pathway in Plocamium brasiliense cortical cells (Rhodophyta).
abstract: This paper has identified, for the first time in a member of the Rhodophyta, a vacuolar organelle containing enzymes that are involved in the mevalonate pathway-an important step in red algal isoprenoid biosynthesis. These organelles were named mevalonosomes (Mev) and were found in the cortical cells (CC) of Plocamium brasiliense, a marine macroalgae that synthesizes several halogenated monoterpenes. P. brasiliense specimens were submitted to a cytochemical analysis of the activity of the 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS). Using transmission electron microscopy (TEM), we confirmed the presence of HMGS activity within the Mev. Because HMGS is necessary for the biosynthesis of halogenated monoterpenes, we isolated a hexanic fraction (HF) rich in halogenated monoterpenes from P. brasiliense that contained a pentachlorinated monoterpene as a major metabolite. Because terpenes are often related to chemical defense, the antifouling (AF) activity of pentachlorinated monoterpene was tested. We found that the settlement of the mussel Perna perna was reduced by HF treatment (2.25 times less than control; 40% and 90% of fouled surface, respectively; P = 0.001; F9,9 = 1.13). The HF (at 10 μg · mL(-1) ) also inhibited three species of fouling microalgae (Chlorarachnion reptans, Cylindrotheca cloisterium, and Exanthemachrysis gayraliae), while at a higher concentration (50 μg · mL(-1) ), it inhibited the bacteria Halomonas marina, Polaribacter irgensii, Pseudoalteromonas elyakovii, Shewanella putrefaciens, and Vibrio aestuarianus. The AF activity of P. brasiliense halogenated monoterpenes and the localization of HMGS activity inside Mev suggest that this cellular structure found in CC may play a role in thallus protection against biofouling.
authors.affiliation: Departamento de Biologia Marinha, Universidade Federal Fluminense, Outeiro São João Batista, s/no., Niterói, Rio de Janeiro, Brazil.
authors.forename: Wladimir Costa
authors.initials: WC
authors.lastname: Paradas
authors.affiliation: Diretoria de Pesquisas, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão, 915, Rio de Janeiro, Brazil.
authors.forename: Thalita Mendes
authors.initials: TM
authors.lastname: Crespo
authors.affiliation: Diretoria de Pesquisas, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão, 915, Rio de Janeiro, Brazil.
authors.forename: Leonardo Tavares
authors.initials: LT
authors.lastname: Salgado
authors.affiliation: Centro de Ciências da Saúde, Instituto de Ciências Biomédicas, Departamento de Histologia e Embriologia, Universidade Federal do Rio de Janeiro (UFRJ), Av. Carlos Chagas Filho, 373, bloco: B, sala F2-27, Rio de Janeiro, Brazil.
authors.forename: Leonardo Rodrigues
authors.initials: LR
authors.lastname: de Andrade
authors.affiliation: Núcleo de Pesquisas em Ecologia e Desenvolvimento Social de Macaé, Universidade Federal do Rio de Janeiro, Rua Rotary Club, s/no., São José do Barreto, Macaé, Rio de Janeiro, Brazil.
authors.forename: Angélica Ribeiro
authors.initials: AR
authors.lastname: Soares
authors.affiliation: Université de Bretagne Occidentale, LEMAR UMR 6539, IUEM - Technopole Brest-Iroise, Rue Dumont d'Urville, Plouzané, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Hellio
authors.affiliation: Departamento de Biologia Marinha, Universidade Federal Fluminense, Outeiro São João Batista, s/no., Niterói, Rio de Janeiro, Brazil.
authors.forename: Ricardo Rogers
authors.initials: RR
authors.lastname: Paranhos
authors.affiliation: Diretoria de Pesquisas, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão, 915, Rio de Janeiro, Brazil.
authors.forename: Lilian Jorge
authors.initials: LJ
authors.lastname: Hill
authors.affiliation: Diretoria de Pesquisas, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão, 915, Rio de Janeiro, Brazil.
authors.forename: Geysa Marinho
authors.initials: GM
authors.lastname: de Souza
authors.affiliation: Departamento de Biologia Geral, Universidade Federal Fluminense, Outeiro São João Batista, s/no., Niterói, Rio de Janeiro, Brazil.
authors.forename: Alphonse Germaine Albert Charles
authors.initials: AG
authors.lastname: Kelecom
authors.affiliation: Departamento de Biologia Marinha, Universidade Federal Fluminense, Outeiro São João Batista, s/no., Niterói, Rio de Janeiro, Brazil.
authors.forename: Bernardo Antônio Perez
authors.initials: BA
authors.lastname: Da Gama
authors.affiliation: Departamento de Biologia Marinha, Universidade Federal Fluminense, Outeiro São João Batista, s/no., Niterói, Rio de Janeiro, Brazil.
authors.forename: Renato Crespo
authors.initials: RC
authors.lastname: Pereira
authors.affiliation: Diretoria de Pesquisas, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão, 915, Rio de Janeiro, Brazil.
authors.forename: Gilberto Menezes
authors.initials: GM
authors.lastname: Amado-Filho
keywords: 3-hydroxy-3-methylglutaryl-CoA synthase; Plocamium brasiliense; antifouling activity; chemical defense; cortical cell cytochemistry; halogenated monoterpenes; mevalonate pathway; mevalonosome; osmiophilic bodies