Pax7 Expression and Color Pattern Development in Two Populations of Metriaclima ‘msobo’ from Lake Malawi, Africa
In Lake Malawi, 450-600 species have evolved from one riverine ancestor within the past million years. The dynamic speciation of Lake Malawi’s endemic fauna has coincided with a diversification of color patterns, driven by sexual selection. Little is known about the genes determining male color pattern, despite its importance during population divergence and speciation. This study attempts to identify genes underlying the divergence of male color patterns between two populations of Metriaclima ‘msobo’ from Lake Malawi. Adult males from the Lundo population display blue and black vertical bars, while adult males from the Magunga population have blue and black blotches. The Magunga color pattern is similar to the common orange-blotch (OB) pattern observed in female cichlids, which is controlled by overexpression of the Pax7 gene. The major time points for individual color pattern development were on days 11, 16, and 23. The role of Pax7 was tested on the Magunga specific color pattern using qPCR to examine gene expression during color pattern development between the barred and blotchy populations. Primers for Pax7, as well as for two housekeeping genes (GAPDH and beta-actin), were designed and optimized to normalize qPCR data. Several embryos from three Metriaclima ‘msobo’ species—each from days 11, 16, and 23—were sampled in preparation for qPCR. The total RNA from each of these embryos was analyzed through the Experion chamber and was of optimum purity. cDNA samples were run through qPCR with the optimized primers, combined with SYBR Green fluorescent dye. Bio-Rad qPCR software was used to calculate the amount of Pax7 expression relative to that of the housekeeping genes. The analysis of variance showed that while there was a trend of expression within the Magunga embryos, the standard devations and errors were too large. However, there was no significant difference in Pax7 expression between the Magunga and Lundo populations.