Testis-specific expression patterns of the PIM1 genes and elevated expression level of tree sparrow from polluted site
Even though we have figured out the duplication events of PIM1 in tree sparrow genome, there is still a gap between the PIM1 , known as a proto-oncogene, and rapid evolution of sperm in BY. To further explore the physiological functions of PIM1 and speculate their role in the rapid evolution of sperm under environmental pollution, we measured the expression level of PIM in different tissues (brain, heart, kidney, liver, lung, muscle, spleen, testis) and different sites (BY and LJX). Relative to the chicken PIM1 widely expressed in the eight tissues, we surprisingly find that most of the PIM1genes show testis-specific expression patterns (Figure 3A). In addition to tissue expression profile, the average expression levels ofPIM1 between BY and LJX testis samples are compared. The results turn out that the average expression level of PIM1 is significantly higher in the testis of BY tree sparrow than of LJX while the expression of all transcripts and the copy number of PIM1show no difference (Figure 3B). Besides the average expression, the expression value of almost every single PIM1 duplicate in testis is found to be higher in BY when PIM3 is found to be unchanged (Figure S8).