The multicellular green alga Volvox carteri is an attractive model to study aspects of multicellularity. However, analyses of these aspects require many molecular tools for genetic engineering and so far, there is only a limited number available for Volvox.

In this study, Arvin Hallmann of the University of Bielefield in Germany discovered two new tools for Volvox. First, he discovered that the promoter of the V. carteri nitrate reductase gene (nitA) is a powerful switch for transgene expression. Strong expression can be triggered by changing the nitrogen source from ammonium to nitrate. Hallmann also found that the luciferase (g-luc) gene from copepod (Gaussia princeps) is a suitable reporter gene in V. carteri. The emitted light of the chemiluminescent reaction can be easily detected and quantified with a luminometer.

With these findings, there are now two available molecular tools for genetic engineering of Volvox : the nitrate-inducible promoter of V. carteri and luciferase reporter gene of G. princeps. These will be useful for future research on V. carteri.

For more information, read the full article on BioMed Central site. 

Figure 1. The phenotype ofV. carteri: wild-type and transformant.V. carteri consists of ~2000 small, biflagellate, terminally differentiated, somatic cells at the surface and ~16 large reproductive cells in the interior of a spheroid. The reproductive cells develop inside the mother spheroid to embryos and later to juveniles. Up to 99% of the volume of such a spheroid consists of a complex, transparent, glycoprotein-rich extracellular matrix that holds all of the cells in place. (A) Wild-type spheroid of Volvox carteri f. nagariensis short before release of ~16 juvenile spheroids. (B) Spheroid of transformant NitLuc-A172 functionally expressing the G. princeps luciferase gene under control of the V. carteri nitA promoter. Transformant NitLuc-A172 shows the same phenotype as its wild-type parent.