Metabolite and transcriptomic analysis reveals metabolic and regulatory features associated with Powell orange pulp deterioration during room temperature and cold storage

Abstract

Fruit senescence is an inevitable developmental process that involves dynamic alterations in many metabolic and regulatory pathways. In this study, GC–MS and RNA-Seq were employed to characterize the metabolite and transcriptomic profiles during postharvest storage under room temperature (RT) and low temperature (LT) in Powell (Citrus sinensis) fruits. Results showed that RT-storage up-regulated genes involved in primary metabolism including sucrose metabolism, glycolysis, gluconeogenesis, fermentation and GABA shunt pathways, resulting in declines of sucrose and organic acids such as malate, citrate and α-ketoglutaric acid, and accumulations of hexoses and GABA. Furthermore, calcium-sensor proteins were strongly induced including CMLs, CBL-CIPKs and CPKs, indicating the potential roles of calcium signaling during postharvest storage under RT. RT-storage enhanced ABA and ethylene signaling pathways via up-regulation of PYLs, ABI5 and ERFs, which revealed hormone regulatory networks on fruit senescence. In addition, the induced RPLs, NAC and WRKY transcription factors and MAP kinases provided a comprehensive view on the fruit senescence regulation. During LT storage, the levels of metabolites and catabolism related genes were substantially maintained, and auxin signal was modulated by upregulation of TIR1 and downregulation of Aux/IAAs. In summary, RT storage accelerates calcium, ABA and ethylene signals, which could positively regulate fruit senescence and result in induced primary metabolism and fruit quality deterioration. LT storage might accelerate the auxin signal, thus delaying senescence and maintaining fruit quality.