Poster Presentation Society for Molecular Biology and Evolution Conference 2016

Rapid expansion of pigmentation genes in Penaeid prawns with absolute conservation of gene function. (#479)

Alyssa Budd 1 , Mark Tonks 2 , Sue Cheers 1 , Tracey M Hinton 3 , Nicholas M Wade 1
  1. Aquaculture Program, CSIRO Agriculture and Food, Brisbane, QLD, Australia
  2. Aquaculture Program, CSIRO Agriculture and Food, Brisbane, QLD, Australia
  3. Australian Animal Health Laboratory, CSIRO Biosecurity, Geelong, VIC, Australia

Crustaceans have a unique mechanism for producing their colour (Wade et al., 2009). The red carotenoid astaxanthin (Axn) is the central chromophore to a protein complex called crustacyanin (CRCN) that modifies the colour of Axn to any other colour in the visible spectrum. In this way, crustaceans produce their cryptic shell colours and patterns that are used in camouflage, survival, reproduction and communication. Traditionally, there were only thought to be 2 genes encoding crustacean colour proteins, CRCN-A and CRCN-C. Using a combination of degenerate PCR and next generation sequence data mining, this study identified 36 potential new CRCN genes from 11 species of Penaeid prawns, with some species containing up to 6 different CRCN isoforms. Despite their nucleotide sequence differences, the ratio of non-synonymous to synonymous mutations showed that the majority of sequences had significant evidence of stabilising selection. As a consequence, predictive 3D structure modelling showed absolute preservation of CRCN-A or CRCN-C structure across all sequences. In Penaeus monodon, RNA interference was used to functionally down-regulate three different CRCN isoforms, and this caused distinct gene-specific colour changes depending on which CRCN isoform was down regulated. Expression of these three isoforms was also differentially regulated across the moult cycle. These results demonstrate that these are functional CRCN gene isoforms, and that there has been a rapid expansion of the CRCN gene lineage in Penaeid prawns. Our study showed that the production and regulation of pigmentation in crustaceans is more complex than initially thought, but the mechanism by which colour is produced in crustaceans is strictly conserved.

  1. Wade NM, Tollenaere A, Hall MR and Degnan BD (2009) Molecular Biology and Evolution 26(8):1851–1864.