Ancient Duplications Have Led to Functional Divergence of Vitellogenin-Like Genes Potentially Involved in Inflammation and Oxidative Stress in Honey Bees.

Abstract

Protection against inflammation and oxidative stress is key in slowing down aging processes. The honey bee (Apis mellifera) shows flexible aging patterns linked to the social role of individual bees. One molecular factor associated with honey bee aging regulation is vitellogenin, a lipoglycophosphoprotein with anti-inflammatory and antioxidant properties. Recently, we identified three genes in Hymenopteran genomes arisen from ancient insect vitellogenin duplications, named vg-like-A, -B, and -C. The function of these vitellogenin homologs is unclear. We hypothesize that some of them might share gene- and protein-level similarities and a longevity-supporting role with vitellogenin. Here, we show how the structure and modifications of the vg-like genes and proteins have diverged from vitellogenin. Furthermore, all three vg-like genes show signs of positive selection, but the spatial location of the selected protein sites differ from those found in vitellogenin. We show that all these genes are expressed in both long-lived winter worker bees and in summer nurse bees with intermediate life expectancy, yet only vg-like-A shows elevated expression in winter bees as found in vitellogenin. Finally, we show that vg-like-A responds more strongly than vitellogenin to inflammatory and oxidative conditions in summer nurse bees, and that also vg-like-B responds to oxidative stress. We associate vg-like-A and, to lesser extent, vg-like-B to the antiaging roles of vitellogenin, but that vg-like-C probably is involved in some other function. Our analysis indicates that an ancient duplication event facilitated the adaptive and functional divergence of vitellogenin and its paralogs in the honey bee.