Comparative Analysis of the Transcriptomes of Persisting and Abscised Fruitlet

Pecan is one of the famous nut species in the world.In this study we have conducted a transcriptomic profiling of persisting and abscised fruitlets in early fruit development by RNAseq. A total of 11,976 DEGs was identified with 3,012 upregulated DEGs and 8,964 downregulated DEGs in the comparison of abscised fruitlets vs persisting fruitlets at 35 DAA. Our transcriptomic data suggested that gene subsets encoding elements involved biosynthesis, metabolism, perception, signal transduction, and cross talk of plant hormones ABA, auxin, cytokinin, ethylene, and GA and plant growth regulators jasmonates, salicylic acid, and brassinosteroids were expressed differentially. And majority of the transcriptionally activated genes in-volved in hormone signaling were downregulation in the abscised fruitlets except for the eth-ylene and salicylic acid signaling. The differentially expression of transcripts coding for en-zymes involved in sucrose, glucose, trehalose, starch, galactose and galactinol metabolism, showing that sucrose, galactinol, and glucose synthesis was reduced, and starch content was re-duced as the starch biosynthesis blocked and retrogradation and degradation intensified. These results suggested that the abscised fruitlets were stopped growing and developing for some time before drops, thus further indicating sugar supply was reduced or stopped in abscising fruitlet in pecan. The transcriptome characterization described in this manuscript contributes to unravel-ling the molecular mechanisms and pathways involved in the physiological abscission of pecan fruits.