Balakirev ES et al. (2012), Symbiotic associations in the phenotypically-di...

ECB-ART-42484

PLoS One 2012 Jan 01;76:e39587. doi: 10.1371/journal.pone.0039587.

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Symbiotic associations in the phenotypically-diverse brown alga Saccharina japonica.

Balakirev ES , Krupnova TN , Ayala FJ .

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The brown alga Saccharina japonica (Areschoug) Lane, Mayes, Druehl et Saunders is a highly polymorphic representative of the family Laminariaceae, inhabiting the northwest Pacific region. We have obtained 16S rRNA sequence data in symbiont microorganisms of the typical form (TYP) of S. japonica and its common morphological varieties, known as "longipes" (LON) and "shallow-water" (SHA), which show contrasting bathymetric distribution and sharp morphological, life history traits, and ecological differences. Phylogenetic analysis of the 16S rRNA sequences shows that the microbial communities are significantly different in the three forms studied and consist of mosaic sets of common and form-specific bacterial lineages. The divergence in bacterial composition is substantial between the TYP and LON forms in spite of their high genetic similarity. The symbiont distribution in the S. japonica forms and in three other laminarialean species is not related to the depth or locality of the algae settlements. Combined with our previous results on symbiont associations in sea urchins and taking into account the highly specific character of bacteria-algae associations, we propose that the TYP and LON forms may represent incipient species passing through initial steps of reproductive isolation. We suggest that phenotype differences between genetically similar forms may be caused by host-symbiont interactions that may be a general feature of evolution in algae and other eukaryote organisms. Bacterial symbionts could serve as sensitive markers to distinguish genetically similar algae forms and also as possible growth-promoting inductors to increase algae productivity.

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Genes referenced: LOC100887844 LOC100893907 lonp1

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References [+] :

Ashen, Molecular and ecological evidence for species specificity and coevolution in a group of marine algal-bacterial symbioses. 2000, Pubmed

	Figure 1. Neighbor-joining tree of 16S rRNA sequences of Saccharina japonica symbionts, based on Kimura's 2-parameter distance.We used two representative phylotypes to illustrate bacterial diversity for each Proteobacteria genus. The numbers at the nodes are bootstrap percent probability values based on 10,000 replications. rRNA algae plastid genes are used as outgroup. Gammaproteobacteria and Betaproteobacteria phylotypes are marked by vertical lines. Other comments see Table 1.
	Figure 2. UPGMA distance tree of the Saccharina japonica morphological forms based on the bacterial contents they carry.The scale bar shows the distance between clusters in UniFrac units [31]: a distance of 0 means that two environments are identical, and a distance of 1 means that two environments contain mutually exclusive lineages. Scale: 1 dash ∼ 0.0033 branch length units. Three individuals for each morphological form, the TYP (TYP-2, TYP-3, and TYP-4), LON (LON-1, LON-2, and LON-3), and SHA (SHA-1, SHA-2, and SHA-4) are used for the bacterial content analysis. For sample abbreviations see “Materials and Methods”.
	Figure 3. Two principal coordinates from a principal coordinate analysis of the Proteobacteria sequences obtained from three morphological forms (A) or species along with the forms (B).The numbers on the axes refer to the percent of the variation explained by each principal component (P1 and P2). Other comments see Figure 2.