A case study of a micro-inversion event in dark brown fibre cotton (Gossypium hirsutum)

Structural variation is a major type of genetic variation that can potentially induce powerful genetic effects. In this study, we examined the Inv(A07)p1.09p2.23 genetic inversion in brown fibre cotton at the individual and population genetics levels. A dark-brown fibre mutant that resulted from a distant hybridization between Gossypium barbadense and G. hirsutum, and a natural population including 30 dark-brown, 70 light-brown and 21 white fibre cotton accessions were collected to perform a functional study of this micro-inversion. The results showed that Inv(A07)p1.09p2.23 can be detected by high-throughput resequencing method, and induce micro-deletion, gene disruption (Ghir_A07G000980) and abnormal gene expression in the breakpoint regions. Inv(A07)p1.09p2.23 existed in only dark-brown fibre cotton, had undergone negative selection in elite brown fibre cultivars, and was significantly associated with fibre colour and nine fibre traits. In the Inv(A07)p1.09p2.23 region, nucleotide diversity was lower, recombination was absent, and linkage disequilibrium was higher. Overall, this inversion event in dark-brown fibre cotton produced significant genetic effects, and this study will guide us to better understand the genetic effects of inversion events in dark-brown fibre cotton.