Cucumber ovaries inhibited by dominant fruits still respond to pollination but display distinct metabolome and transcriptome profiles

Cucurbits represent an attractive model to explore the dynamics of fruit set. Here we set out to characterize first fruit inhibition (FFI), i.e. the inhibitory effect of the first fruits on subsequent development of younger ovaries during pollination induced fruit set. After the first fertilized ovaries set fruit, younger ovaries fertilized above them on the main stem remained in a temporary state of inhibition. During this stage, the ovaries preserved their size and green color, and if the older fruits were removed within a one-week reversibility window, the inhibited ones set fruit. We compared the gene expression profiles of pollinated ovaries (committed to set fruits) with respect both to those affected by FFI and to non-pollinated ovaries (comitted to senescence). The three fates of the ovaries were characterized at 1 day post anthesis, compare to anthesis, by wide changes in gene expression, with several specific transcripts being up- or down-regulated in response to the presence (or absence) of pollination. Metabolic profiling was undertaken and integrated with the transcriptomic data in order to characterize early physiological changes that occur in post-anthesis ovaries in parthenocarpic and non-parthenocarpic genotypes.