Volvox 2015: cell differentiation

One of the most studied aspects of Volvox development is the differentiation of its 2000 or so cells into two types: a few (usually 12-16) large reproductive cells (germ) and the rest small, biflagellate cells that provide motility (soma). The main genes controlling this differentiation have long been known, but the details of how they work are still being worked out.

Erik Hanschen (left) with Cristian Solari, David Smith, and Jillian Walker

Erik Hanschen (left) with Cristian Solari, David Smith, and Jillian Walker

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Evolution of eusociality

Last month, two papers on the evolution of eusociality were published in high-profile journals: one by Karen M. Kapheim and colleagues in Science, the other by Sandra M. Rehan and Amy L. Toth in Trends in Ecology & Evolution (TREE). Social and eusocial insects are an attractive system for studying major transitions, sharing some of the key features that make the volvocine algae so good for this purpose: multiple, independent origins of traits thought to be important to the transition and extant species with intermediate levels of sociality. These features make the social insects, like the volvocine algae, well-suited for comparative studies.
Figure 1 from Rehan & Toth: (A) Overview of phylogeny of aculeate Hymenoptera (with the nonhymenopteran but eusocial termites as an outgroup), highlighting independent origins of sociality (colored branches), groups with species ranging from solitary to primitively social (green), primitively social to advanced eusocial (orange), solitary to advanced eusocial (blue), and all species advanced eusocial (grey). (B) The full range of the solitary to eusocial spectrum (blue) and predictions of which genomic mechanisms are hypothesized to operate at different transitional stages of social evolution (broken arrows).

Figure 1 from Rehan & Toth: (A) Overview of phylogeny of aculeate Hymenoptera (with the nonhymenopteran but eusocial termites as an outgroup), highlighting independent origins of sociality (colored branches), groups with species ranging from solitary to primitively social (green), primitively social to advanced eusocial (orange), solitary to advanced eusocial (blue), and all species advanced eusocial (grey). (B) The full range of the solitary to eusocial spectrum (blue) and predictions of which genomic mechanisms are hypothesized to operate at different transitional stages of social evolution (broken arrows).

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Actin evolution in the Volvocales

Kato-Minoura Figure 1

Fig. 1 from Kato-Minoura et al. 2015: Genomic structure of volvocine actin and NAP genes. For comparison, previously identified sequences are also shown. Filled boxes, putative coding exons; open boxes, putative 5′ and 3′ untranslated regions. Intervening sequences are shown by solid lines. Intron positions are indicated by codon and phase numbers with reference to the three alpha-actins of vertebrates (377 amino acids) (Weber and Kabsch 1994). The conserved intron positions are linked with dotted lines. ATG, translation start codon; TAA or TGA, stop codon.

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