Profiling gibberellin (GA3)-responsive genes in mature mandarin fruit using a citrus 22K oligoarray

Gibberellin3 (GA3)-responsive genes were investigated with a citrus 22K oligoarray1 to further the understanding of transcriptional regulation by GA3 treatment in Satsuma mandarin fruit (Citrus unshiu Marc.). 213 GA3-responsive genes were identified that showed a 3-fold or greater expression change after 72 h GA3 treatment, compared to expression after 72 h air treatment. GA3 treatment induced expression of pathogenesis-related (PR) proteins and genes that function in photosynthesis, chloroplast biogenesis, resistance, defense and stress. Also, GA3 treatment reduced the transcription of several ethylene-inducible genes, such as carotenoid metabolic genes, which are associated with fruit ripening.Contrasting effects between GA3 and ethylene were observed on photosynthesis and chloroplast biogenesis, chlorophyll metabolism, and carotenoid metabolism, indicating that the endogenous GA3 level might be important for the endogenous regulation of maturation and senescence in mature citrus fruit. It was also found that the GA response pathway was likely to take part in cross-talk with the pathogen-related pathway in mature citrus fruit.