An Advanced Filter-Feeder Hypothesis for Urochordate Evolution

Satoh, Nori

doi:10.2108/zsj.26.97

Cited by 36 publications

(28 citation statements)

References 142 publications

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“…Nevertheless, global synteny is conserved between cephalochordates and vertebrates (Putnam et al, 2008) but not between urochordates and vertebrates (Dehal et al, 2002). This strongly suggests that urochordates diverged from the main line connecting ancestral chordates to vertebrates (e.g., Satoh, 2008), possibly due to their success as sessile and filter-feeders (Satoh, 2009). A similar argument has been made to explain the divergent mode of gene regulatory networks in ascidian embryogenesis (Imai et al, 2006;Lemaire, 2006).…”

Section: Figmentioning

confidence: 67%

Direct examination of chromosomal clustering of organ‐specific genes in the chordate Ciona intestinalis

Shoguchi

Hamada

Fujie

et al. 2011

Genesis

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Summary: One of challenges in the field of developmental biology is to understand how spatially and/or temporally coordinated expression of genes is controlled at the chromosomal level. It remains controversial whether genes expressed in a given tissue are randomly distributed throughout a given animal genome, or instead resolve into clusters. Here we used microarray analysis to identify more than 1,700 genes that are expressed preferentially in each of 11 organs of the chordate Ciona intestinalis adult, and determined the location of these genes on the 14 pairs of Ciona chromosomes. In spite of extensive mapped gene analysis, we only confirmed small clusters containing two or three genes. Our result indicates that organ-specific genes are distributed rather evenly all over chromosomes, suggesting that the notion of clustering of organ-specific genes in animal genomes is not generally applicable to this chordate. genesis 49:662-672, 2011. V V C 2011 Wiley-Liss, Inc.

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Section: Figmentioning

confidence: 67%

Direct examination of chromosomal clustering of organ‐specific genes in the chordate Ciona intestinalis

Shoguchi

Hamada

Fujie

et al. 2011

Genesis

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“…It remains a point of debate as to whether tail loss or retention is more representative of the ancestral tunicate. The morphological data suggests larvaceans are neotenic (Stach, 2008a), whereas molecular phylogenetic data (Delsuc et al, 2006;Delsuc et al, 2008) and a filter-feeding hypothesis on urochordate evolution (Satoh, 2009) places them basal to ascidians. Whereas repression of metamorphic initiation by Ci-CesA and/or cellulose in ascidians is alleviated through tail loss, in larvaceans the tail must be retained in juveniles and adults as an integral part of the feeding mechanism.…”

Section: Research Articlementioning

confidence: 97%

Functional specialization of cellulose synthase genes of prokaryotic origin in chordate larvaceans

Sagane¹,

Zech²,

Bouquet³

et al. 2010

Development

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SUMMARYExtracellular matrices play important, but poorly investigated, roles in morphogenesis. Extracellular cellulose is central to regulation of pattern formation in plants, but among metazoans only tunicates are capable of cellulose biosynthesis. Cellulose synthase (CesA) gene products are present in filter-feeding structures of all tunicates and also regulate metamorphosis in the ascidian Ciona. Ciona CesA is proposed to have been acquired by lateral gene transfer from a prokaryote. We identified two CesA genes in the sister-class larvacean Oikopleura dioica. Each has a mosaic structure of a glycoslyltransferase 2 domain upstream of a glycosyl hydrolase family 6 cellulase-like domain, a signature thus far unique to tunicates. Spatial-temporal expression analysis revealed that Od-CesA1 produces long cellulose fibrils along the larval tail, whereas Od-CesA2 is responsible for the cellulose scaffold of the postmetamorphic filter-feeding house. Knockdown of Od-CesA1 inhibited cellulose production in the extracellular matrix of the larval tail. Notochord cells either failed to align or were misaligned, the tail did not elongate properly and tailbud embryos also exhibited a failure to hatch. Knockdown of Od-CesA2 did not elicit any of these phenotypes and instead caused a mild delay in pre-house formation. Phylogenetic analyses including Od-CesAs indicate that a single lateral gene transfer event from a prokaryote at the base of the lineage conferred biosynthetic capacity in all tunicates. Ascidians possess one CesA gene, whereas duplicated larvacean genes have evolved distinct temporal and functional specializations. Extracellular cellulose microfibrils produced by the premetamorphic Od-CesA1 duplicate have a role in notochord and tail morphogenesis.

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“…Indeed, it is more plausible to consider the dorsal, hollow, neural tube as evolutionarily independent of the ciliary band of dipleurula larvae (see also discussion in §4d). In this sense, the auricularia hypothesis appears to have faded in light of recent evo-devo studies of deuterostomes [18,55].…”

Section: (B) the Auricularia Hypothesismentioning

confidence: 99%

“…It should be noted that the inversion hypothesis cannot necessarily explain the occurrence of chordate-specific structures or the notochord [18,55]. The notochord is a dorsal, midline structure, profoundly associated with the so-called 'organizer' of vertebrate embryos [68].…”

Section: (C) the Inversion Hypothesismentioning

confidence: 99%

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Chordate evolution and the three-phylum system

2014

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Traditional metazoan phylogeny classifies the Vertebrata as a subphylum of the phylum Chordata, together with two other subphyla, the Urochordata (Tunicata) and the Cephalochordata. The Chordata, together with the phyla Echinodermata and Hemichordata, comprise a major group, the Deuterostomia. Chordates invariably possess a notochord and a dorsal neural tube. Although the origin and evolution of chordates has been studied for more than a century, few authors have intimately discussed taxonomic ranking of the three chordate groups themselves. Accumulating evidence shows that echinoderms and hemichordates form a clade (the Ambulacraria), and that within the Chordata, cephalochordates diverged first, with tunicates and vertebrates forming a sister group. Chordates share tadpole-type larvae containing a notochord and hollow nerve cord, whereas ambulacrarians have dipleurula-type larvae containing a hydrocoel. We propose that an evolutionary occurrence of tadpole-type larvae is fundamental to understanding mechanisms of chordate origin. Protostomes have now been reclassified into two major taxa, the Ecdysozoa and Lophotrochozoa, whose developmental pathways are characterized by ecdysis and trochophore larvae, respectively. Consistent with this classification, the profound dipleurula versus tadpole larval differences merit a category higher than the phylum. Thus, it is recommended that the Ecdysozoa, Lophotrochozoa, Ambulacraria and Chordata be classified at the superphylum level, with the Chordata further subdivided into three phyla, on the basis of their distinctive characteristics.

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An Advanced Filter-Feeder Hypothesis for Urochordate Evolution

Cited by 36 publications

References 142 publications

Direct examination of chromosomal clustering of organ‐specific genes in the chordate Ciona intestinalis

Direct examination of chromosomal clustering of organ‐specific genes in the chordate Ciona intestinalis

Functional specialization of cellulose synthase genes of prokaryotic origin in chordate larvaceans

Chordate evolution and the three-phylum system

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