Insights Into the Relationships Between the Distribution of Repetitive Dna Sequences and the Flowering Time of Maize

Over 80% of the maize genome consists of repetitive DNA, primarily transposable elements (TEs) and satellite DNA (satDNA). While satDNA organizes major heterochromatic blocks, TEs drive genomic changes and influence gene expression and recombination rates. Although recent literature suggests that the repetitive fraction may modulate flowering time, a complex quantitative trait involving hundreds of regulatory genes, the specific relationship between this repetitive DNA fraction and flowering remains poorly understood in maize. We investigated genomic differences between maize germplasms with contrasting flowering phenology. First, satDNA content (via FISH) and DNA C-values (via flow cytometry) were estimated for a collection of maize of composite origin. Subsequently, in silico mapping of satDNA and TEs was performed using genomes from the Nested Association Mapping (NAM) founder lines. These repetitive sequences were analysed in relation to 14 core flowering-time genes in the sequenced samples. Our findings revealed significant karyotypic variation in the satDNA fraction among samples, despite relatively constant DNA C values. In silico mapping analysis identified frequent TE insertions within both exons and introns of the 14 target genes, exhibiting high polymorphism across the different inbred lines. The comparison between satDNA array accumulation and total genome size did not reveal a correlation with maize flowering time, contrary to previous hypotheses. However, the high variability of TE insertions within regulatory genes suggests that these mobile elements are primary candidates for driving the phenotypic diversity observed in maize flowering cycles.