The evolution of multicellularity and the division of labor between different cell types probably required both the alteration of existing genes and the development of novel genes from previously noncoding sequences.
By comparing the genome of the multicellular green algae Volvox carteri with the genome of its unicellular relative Chlamydomonas reinhardtii both potential novel and heavily modified genes could be identified. Some of these genes, which show no similarity to genes from Chlamydomonas or other unicellular algae species, were investigated at the genomic and transcriptional level. Furthermore, a new chimeric gene construct was established for use in Volvox carteri. This construct allows further investigations and consists of the inducible nitrate reductase promoter and a bioluminescent reporter gene, namely the gene of the luciferase from Gaussia princeps.
The results of this work have shown that the group of potentially Volvox-specific genes, which was originally identified as part of the Volvox genome project, is a diverse collection of genes of different ages, origins, functions and taxonomic distributions. The data suggest that some of the examined genes might be specific for multicellular Volvocales. The proof of gene expression and the existence of a relatively long open reading frame show that the genes are no artifacts of gene prediction. Thus, promising candidates for subsequent studies could be identified. Future investigations will show whether these gene families were involved in the development of characteristic features of this lineage and which role they might have played in the development of multicellularity, oogamy or cellular differentiation.
Parts of the work are published in
von der Heyde, E. L., Klein, B., Abram, L., & Hallmann, A. (2015). The inducible nitA promoter provides a powerful molecular switch for transgene expression in Volvox carteri. BMC Biotechnology, 15(1), 5.
Eva Laura von der Heyde conducted this work in the Department for Cellular and Developmental Biology of Plants in the working group of Prof. Dr. Armin Hallmann.