Intraspecific Differentiation of Secondary Metabolites in the Red Alga Laurencia Nipponica Yamada

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The marine red alga Laurencia nipponica Yamada produces diverse halogenated secondary metabolites. The major metabolites can be divided into two groups : chamigrane sesquiterpenoid group (prepacifenol) and straight-chain C_<15> bromoether group (laureatin, laurencin, epilaurallene, kumausallene, isoprelaurefucin, isolaurallene and laurefucin). Major halogenated compounds in 36 local populations from the whole geographical range of this species in Japan were investigated using HPLC. These matabolites characterize each local population. Laureatin-producing populations predominate along the coast of the Sea of Japan, laurencin-producing populations chiefly occur along the Pacific coast of northern Honshu. Prepacifenol-producing populations predominate along the Pacific coast of Hokkaido. Populations producing other metabolites are locally limited in Hokkaido. The diversity of secondary metabolites of this species might be established at northerly localities of its geographical distributio … More n. At some localities populations producing different metabolites are sympatric. These chemically different populations are morphologically comparable and are not reproductively isolated. The populations can be treated as races (chemical races). Compounds of F_1 tetrasporophytes and F_1 gametophytes of interracial hybrids suggest that gene systems producing enzymes which participate in the process of these metabolite syntheses may be encorded by nuclear genomes and the terpenoid- and bromoether-gene systems may be on different loci of homologous chromosomes and recombination or gene conversion may rarely occur between the chromosomes. Natural hybrids and recombination-type gametophytes were found at a locality and support the experimental results using artificial hybrids. On the basis of geographical distribution of each race and possible synthetic process of the major metabolites race differentiations can be estimated as follows. Laureatin race predominating from southerly to northerly localities along the coast of the Sea of Japan is primitive and other races had been derived from this race by heritable variation bearing two major directions : 1) diversification of bromoether-gene system and 2) occurrence of terpenoid-gene system. Less