Comparative transcriptome analysis during early fruit development between three seedy citrus genotypes and their seedless mutants

Identification of genes with differential transcript abundance (GDTA) in seedless mutants may enhance understanding of seedless citrus development. Transcriptome analysis was conducted at three time points during early fruit development (Phase 1) of three seedy citrus genotypes: Fallglo (Bower citrus hybrid (Citrus reticulata x C. reticulata x C. paradisi) x Temple (C. reticulata x C. sinensis)), grapefruit (C. paradisi), Pineapple sweet orange (C. sinensis), and their seedless mutants. Seed abortion in seedless mutants was observed at 26 days post anthesis (Time point 2). Affymetrix transcriptomic analysis revealed 359 to 1077 probe sets with differential transcript abundance in the comparison of seedless versus seedy fruits for each citrus genotypes and time points. The GDTA identified by 18 microarray probe sets were validated by qPCR. Hierarchical clustering analysis revealed a range of GDTA associated with development, hormone and protein metabolism, all of which may reflect genes associated with seedless fruit development. There were 14, 9 and 12 genes found exhibiting similar abundance ratios in all three seedless versus seedy genotype comparisons at time point 1, 2 and 3, respectively. Among those genes were genes coding for an aspartic protease and a cysteine protease, which may play important roles in seedless fruit development. New insights into seedless citrus fruit development may contribute to biotech approaches to create seedless cultivars.