Abstract
BackgroundMelon (Cucumis melo) is an important vegetable crop from the Cucurbitaceae family and a reference model specie for sex determination, fruit ripening and vascular fluxes studies. Nevertheless, the nature and role of its epigenome in gene expression regulation and more specifically in sex determination remains largely unknown.ResultsWe have investigated genome wide H3K27me3 and H3K9ac histone modifications and gene expression dynamics, in five melon organs. H3K9ac and H3K27me3 were mainly distributed along gene-rich regions and constrained to gene bodies. H3K9ac was preferentially located at the TSS, whereas H3K27me3 distributed uniformly from TSS to TES. As observed in other species, H3K9ac and H3K27me3 correlated with high and low gene expression levels, respectively. Comparative analyses of unisexual flowers pointed out sex-specific epigenetic states of TFs involved in ethylene response and flower development. Chip-qPCR analysis of laser dissected carpel and stamina primordia, revealed sex-specific histone modification of MADS-box genes. Using sex transition mutants, we demonstrated that the female promoting gene, CmACS11, represses the expression of the male promoting gene CmWIP1 via deposition of H3K27me3.ConclusionsOur findings reveal the organ-specific landscapes of H3K9ac and H3K27me3 in melon. Our results also provide evidence that the sex determination genes recruit histone modifiers to orchestrate unisexual flower development in monoecious species.
Highlights
Melon (Cucumis melo) is an important vegetable crop from the Cucurbitaceae family and a reference model specie for sex determination, fruit ripening and vascular fluxes studies
To gain new information on the epigenetic control of sex determination, we have examined the genome-wide landscape of H3K27me3 and H3K9ac histone modifications and gene expression dynamics, in five melon organs, focusing our analysis on unisexual flowers
We found that the ethylene-responsive factor (ERF) family displayed the highest number of gene members, consistent with previous studies that reported the role of ethylene and ethylene transduction pathways in sex determination in the cucurbitaceae family (22)
Summary
Melon (Cucumis melo) is an important vegetable crop from the Cucurbitaceae family and a reference model specie for sex determination, fruit ripening and vascular fluxes studies. Melon (Cucumis melo) belongs to the Cucurbitaceae family that includes about 800 species. DNA conformation can be modified by the addition or removal of chemical groups at specific N-terminal residues of histones [8, 9]. Some of these modifications are in charge of genome connectivity and heterochromatin stability, while others regulate gene expression or repression along the euchromatic regions. Genome-wide analyses of epigenetic landscapes have been performed in several species including Arabidopsis [14,15,16,17], maize [18,19,20], rice [21,22,23], common bean [24] and barley [25]
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