cDNA-AFLP analysis reveals altered gene expression profiles involved in juice sac granulation in pummelo(Citrus grandis)

Citrus fruits produced in China are often affected by granulation.Granulation is an altered physiological state of citrus fruits occurring usually before harvest but whose underlying mechanisms remain elusive.In this study,cDNA-AFLP technology enabled the identification of 116 granulation-associated genes in pummelo(C.grandis)juice sacs.Differentially expressed transcript-derived fragments(TDFs)were shown to be mainly involved in biological regulation and signal transduction,carbohydrate and energy metabolism,nucleic acid,protein metabolism,stress responses,and cell metabolism.Therefore,granulation in pummelo juice sacs seems to involve the following alterations:(1)changes in hormone levels;(2)activation of metabolic pathways related to ATP and sugar synthesis to produce more energy;(3)nucleic acid accumulation and increased protein degradation;(4)activation of stress-responsive metabolic pathways;(5)accelerated juice sac senescence.Our findings provide an overview of differential responses occurring at the transcriptional level in granulated juice sacs,thus revealing new insights into the adaptive mechanisms underlying this altered physiological state in‘Guanximiyou'pummelo(C.grandis)juice sacs.