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

Abstract

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 (CitACS4), 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 CitACS4, the C364W mutation located in the conserved box 6 was co-segregated with andromonoecy. Enzymatic analyses showed that the C364W mutation caused a reduced activity in CitACS4. We believe that the reduced CitACS4 activity may hamper the programmed cell death in stamen primordia, leading to the formation of hermaphroditic flowers.

A unique chromosome translocation disrupting ClWIP1 leads to gynoecy in watermelon

“…In this study, as shown by the DEGs depicted in Table S5, the ethylene biosynthesis gene ACS was upregulated in the gynoecious lines. This result supports prior studies indicating that CitAC4 (Cla011230) is a key gene required for stamen arrest during female flower development in watermelon (Ji et al, 2016;Manzano et al, 2016). We noticed that three notably upregulated genes in the gynoecious lines were associated with cytokinin.…”

“…The proposed genotype for each of the six sex forms in watermelon is as follows: monoecious (A_Gy_Tm), trimonoecious (A_Gy_tmtm), andromonoecious (aaGy_Tm_ or aaGy_tmtm), gynoecious (A_gygyTm_), gynomonoecious (A_gygytmtm) and hermaphrodite (aagygyTm_ or aagygytmtm) (Ji et al, 2015). The a locus has been identified and encodes a 1-aminocyclopropane-1-carboxylic synthase (ACS) gene CitACS4 (Boualem et al, 2016;Ji et al, 2016;Manzano et al, 2016). The enzyme ACS is important in the ethylene biosynthesis pathway, and an activity-reduced mutation, C364W, within its conserved region led to andromonoecy from monoecy in watermelon (Ji et al, 2016;Manzano et al, 2016).…”

“…The a locus has been identified and encodes a 1-aminocyclopropane-1-carboxylic synthase (ACS) gene CitACS4 (Boualem et al, 2016;Ji et al, 2016;Manzano et al, 2016). The enzyme ACS is important in the ethylene biosynthesis pathway, and an activity-reduced mutation, C364W, within its conserved region led to andromonoecy from monoecy in watermelon (Ji et al, 2016;Manzano et al, 2016). It has been reported that activity-reduced or loss mutations of ACS genes in cucumber (Cucumis sativus), melon (Cucumis melo) and squash (Cucurbita pepo) led from monoecy to andromonoecy (Boualem et al, 2008(Boualem et al, , 2009Mart ınez et al, 2013;Ji et al, 2016).…”

“…The enzyme ACS is important in the ethylene biosynthesis pathway, and an activity-reduced mutation, C364W, within its conserved region led to andromonoecy from monoecy in watermelon (Ji et al, 2016;Manzano et al, 2016). It has been reported that activity-reduced or loss mutations of ACS genes in cucumber (Cucumis sativus), melon (Cucumis melo) and squash (Cucurbita pepo) led from monoecy to andromonoecy (Boualem et al, 2008(Boualem et al, , 2009Mart ınez et al, 2013;Ji et al, 2016). These studies showed that the role of ACS in sex determination in the family Cucurbitaceae was conserved, although differing downstream effects were observed depending on species (Boualem et al, 2015).…”

Mapping a Partial Andromonoecy Locus in Citrullus lanatus Using BSA-Seq and GWAS Approaches

“…By taking into account the andromonoecious index (AI) (Martıńez et al, 2014), as well as studying the sex phenotypes of these control lines, more than 200 C. lanatus accessions were separated into three sex phenotypic classes: monoecious (plants with AI=1-1.35), partially andromonoecious (plants with AI=1.35-2.7), and andromonoecious (plants with AI=2.7-3). It has been reported that andromonoecy phenotype is caused by the CitACS4 mutant allele m (Boualem et al, 2016;Ji et al, 2016;Manzano et al, 2016), although is also responsible for PA under heterozygous conditions. So, MM and mm plants are monoecious and andromonoecious, respectively, while Mm are PA, with AI ranging from 1.35 to 2.7 (Manzano et al, 2016).…”