Mutation in the gene encoding 1-aminocyclopropane-1-carboxylate synthase 4 (CitACS4) led to andromonoecy in watermelon

摘要

Although it has been reported previously that ethylene plays a critical role in sex determination in cucurbit species, how the andromonoecy that carries both the male and hermaphroditic flowers is determined in watermelon is still unknown. Here we showed that the watermelon gene 1-aminocyclopropane-1-carboxylate synthase 4(Cit ACS4), expressed specifically in carpel primordia, determines the andromonoecy in watermelon. Among four single nucleotide polymorphism(SNPs) and one InDel identified in the coding region of Cit ACS4, the C364 W mutation located in the conserved box 6 was cosegregated with andromonoecy. Enzymatic analyses showed that the C364 W mutation caused a reduced activity in Cit ACS4. We believe that the reduced Cit ACS4 activity may hamper the programmed cell death in stamen primordia, leading to the formation of hermaphroditic flowers.