Remember the carotenoids? These antioxidants that also let golden staphylococci resist phagocytosis (1)?
Well, they didn’t exactly inherit it vertically from their ancestors, but rather got the genes as a kind gift from some fungus, long long time ago.
I will let you read the study, and uncover the new convoluted link between peas and carrots: Carrots —make–> carotenoids —also synthesized by–> fungi —horizontally transferred to–> pea aphids—infect–> peas (it’s still below six degrees of separation)!
(1) Liu, G., & Nizet, V. (2009). Color me bad: microbial pigments as virulence factors Trends in Microbiology, 17 (9), 406-413 DOI: 10.1016/j.tim.2009.06.006
(2) Moran, N., & Jarvik, T. (2010). Lateral Transfer of Genes from Fungi Underlies Carotenoid Production in Aphids Science, 328 (5978), 624-627 DOI: 10.1126/science.1187113