Integrated Transcriptome and Metabolome Analysis of Mature Stage Sand Pear Fruit Response to High-Temperature Stress

Sand pear is a fruit tree crop with high economic value, widely cultivated in East Asia. However, ripening fruits often suffer from high-temperature stress, which has adverse effects on the quality and yield of the fruit. In this study, we perform high-temperature treatment on mature stage 'Housui' pear fruits. The results showed that heat stress decreased fruit firmness and mineral elements, as well as lead to the flesh appearance of watercore. High temperature induces H₂O₂, MDA, and the antioxidant enzyme activity including SOD, APX, POD, and CAT were significantly increased. Transcriptome and metabolomic analyses revealed that heat stress up-regulated genes related to sucrose synthesis (SPS) while down-regulating those involved in sucrose degradation (SS and NI), resulting in sucrose accumulation. Moreover, the expression of sorbitol dehydrogenase (SDH) and sorbitol transporter (SOT) genes was markedly suppressed, leading to sorbitol accumulation and impaired transport, which promoted watercore development. High temperature also stimulated the expression of ethylene synthesis genes, accelerating abnormal ripening of fruits. In addition, high temperature decreased the accumulation of organic acid and bioactive compounds. Additionally, several antioxidant enzymes genes, five heat shock transcription factors (HSFs) and 34 heat shock protein (HSP) genes were significantly up-regulated. Together, these findings provided new insights into the transcriptional response and metabolomic reprogramming of sand pear response to high-temperature stress.