Duncan et al. (2007): Chlamydomonas reinhardtii, Volvox carteri, and their relatives in the family Volvocaceae provide an excellent opportunity for studying how multicellular organisms with differentiated cell types evolved from unicellular ancestors. While C. reinhardtii is unicellular, V. carteri is multicellular with two cell types, one of which resembles C. reinhardtii cytologically but is terminally differentiated. Maintenance of this "somatic cell" fate is controlled by RegA, a putative transcription factor. We recently showed that RegA shares a conserved region with several predicted V. carteri and C. reinhardtii proteins and that this region, the VARL domain, is likely to include a DNA-binding SAND domain. As the next step toward understanding the evolutionary origins of the regA gene, we analyzed the genome sequences of C. reinhardtii and V. carteri to identify additional genes with the potential to encode VARL domain proteins. Here we report that the VARL gene family, which consists of 12 members in C. reinhardtii and 14 in V. carteri, has experienced a complex evolutionary history in which members of the family have been both gained and lost over time, although several pairs of potentially orthologous genes can still be identified. We find that regA is part of a tandem array of four VARL genes in V. carteri but that a similar array is absent in C. reinhardtii. Most importantly, our phylogenetic analysis suggests that a proto-regA gene was present in a common unicellular ancestor of V. carteri and C. reinhardtii and that this gene was lost in the latter lineage.


Duncan, L; Nishii, I; Harryman, A; Buckley, S; Howard, A; Friedman, NR; Miller, SM. 2007. The VARL gene family and the evolutionary origins of the master cell-type regulatory gene, regA, in Volvox carteri. J. Mol. Evol. 65(1):1-11 PubMed


Name: VARL
Class: TF
Number of species containing the TAP: 3
Number of available proteins: 28

The colour code corresponds to the rules for the domains:

should be contained
should not be contained

Domain rules:

(Domain names are clickable)

Phylogenetic tree for Archeaplastida:

No tree was calculated yet.

TAP distribution:

The following table shows the distribution of VARL over all species included in TAPscan. The values for e.g. a specific kingdom are shown in the tree below if you expand the tree for that kingdom.

Minimum Maximum Average Median Standard deviation

List of species containing VARL sorted by kingdomcladesupergrouporderfamily:

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expand kingdom Archaeplastida (28 proteins in 3 species)
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A list of species letter codes included in the protein names can be found here (opens in new tab).