RT Journal Article SR Electronic T1 Unprecedented reorganization of holocentric chromosomes provides insights into the enigma of lepidopteran chromosome evolution JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP eaau3648 DO 10.1126/sciadv.aau3648 VO 5 IS 6 A1 Hill, Jason A1 Rastas, Pasi A1 Hornett, Emily A. A1 Neethiraj, Ramprasad A1 Clark, Nathan A1 Morehouse, Nathan A1 de la Paz Celorio-Mancera, Maria A1 Cols, Jofre Carnicer A1 Dircksen, Heinrich A1 Meslin, Camille A1 Keehnen, Naomi A1 Pruisscher, Peter A1 Sikkink, Kristin A1 Vives, Maria A1 Vogel, Heiko A1 Wiklund, Christer A1 Woronik, Alyssa A1 Boggs, Carol L. A1 Nylin, Sören A1 Wheat, Christopher W. YR 2019 UL http://advances.sciencemag.org/content/5/6/eaau3648.abstract AB Chromosome evolution presents an enigma in the mega-diverse Lepidoptera. Most species exhibit constrained chromosome evolution with nearly identical haploid chromosome counts and chromosome-level gene collinearity among species more than 140 million years divergent. However, a few species possess radically inflated chromosomal counts due to extensive fission and fusion events. To address this enigma of constraint in the face of an exceptional ability to change, we investigated an unprecedented reorganization of the standard lepidopteran chromosome structure in the green-veined white butterfly (Pieris napi). We find that gene content in P. napi has been extensively rearranged in large collinear blocks, which until now have been masked by a haploid chromosome number close to the lepidopteran average. We observe that ancient chromosome ends have been maintained and collinear blocks are enriched for functionally related genes suggesting both a mechanism and a possible role for selection in determining the boundaries of these genome-wide rearrangements.