METABOLIC PATHWAYS ANALYSIS AND IDENTIFICATION OF HEAT RESPONSE GENES OF PINEAPPLE [ANANAS COMOSUS (L.) MERR.] FRUIT AFFECTED BY ELEVATED POSTHARVEST TEMPERATURE

Pineapple [Ananas comosus (L.) Mem] is an important tropical fruit. The pineapple fruits that are ripened in the high-temperature season have better quality, whereas those ripened in low-temperature season are acidic in taste. Elevated postharvest temperature (EPT) could enhance the quality of winter-harvested pineapple fruit. Based on transcriptome and differentially expressed genes analysis, we explored the GO (Gene Ontology) terms and KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic pathways associated with the EPT treatment and the differentially expressed heat response genes of pineapple fruit after EPT treatment. GO classifications suggested that DEGs (differentially expressed genes) were predominantly annotated to "response to stimulus", "response to external stimulus" and "aromatic compound biosynthetic process" in the biological process ontology, "hydrolase activity" and "glucosidase activity" in the molecular function ontology, as well as "intrinsic to membrane" and "cell wall" in the cellular component ontology. KEGG metabolic pathways analysis revealed that the DEGs were dominantly enriched to "starch and sucrose metabolism", "biosynthesis of secondary metabolites", "pentose and glucuronate interconversions", "carotenoid biosynthesis", "metabolic pathways" "galactose metabolism" and "plant hormone signal transduction". Nineteen HSP (heat shock protein) and sHSP (small HSP) DEGs were screened, and most of them were up-regulated by EPT. Most of the transcription factor genes, including HSF, bHLH, WRKY, MYB, AP2/ERF, bZIP and NAC, were down-regulated by EPT. The SOD (Superoxide dismutase) genes were induced by EPT, while most of the POD (Peroxidase) and CAT (Catalase) genes were repressed. This work would help to understand the molecular mechanisms for EPT process to improve the quality of pineapple fruits.