Loquat (Eriobotrya japonica) is a subtropical tree that blooms in autumn, and its fruits ripen during late spring. Sunburn caused by high temperature and high light intensity is one of the most severe abiotic stress factors that decreases loquat productivity and fruit quality and shelf life, greatly inhibiting sustainable development of this fruit crop industry. To date, little is known about fruit heat tolerance regulation, and investigation of heat stress responses and thermotolerant improvement is important for fruit crops. ‘Wuduiyadanben’ loquat fruits under 40 °C stress were collected for physiological and comparative sequencing analyses; hormone changes in loquat fruit in response to heat stress were investigated using liquid chromatography-mass spectrometry (LC-MS) analysis. Several discriminatory hormone metabolites were identified, including fourteen cytokinins (CK), eight auxins, five jasmonic acids (JA), three gibberellin acids (GA), two abscisic acids (ABA), two salicylic acids (SA), one ethylene (ETH) and one strigolactone (SL). Transcriptomics analysis suggested that genes enriched in ‘Plant hormone signal transduction’, ‘Protein processing in endoplasmic reticulum’, ‘Photosynthesis’, ‘Plant-pathogen interaction’ and ‘Oxidative phosphorylation’ pathways are involved in the heat stress response. Additionally, small RNA analysis further revealed that miRNAs, including miRNA160-x, miRNA393-x, miR6187-x, miR8726-y and novel-m0057–5p, might act together with auxin signaling and heat shock proteins to regulate genes in the heat stress response process. In summary, this study provides a comprehensive understanding of the complex molecular mechanisms underlying the thermal stress responses of loquat fruit.

枇杷（Eriobotrya japonica) 是亚热带乔木，秋季开花，晚春果实成熟。高温和强光引起的晒伤是影响枇杷产量、果实品质和货架期的最严重的非生物胁迫因素之一，极大地阻碍了该果树产业的可持续发展。迄今为止，对水果耐热性调节知之甚少，热应激反应和耐热性改进的研究对水果作物很重要。采集40°C胁迫下的'五对雅丹本'枇杷果实进行生理和比较测序分析；使用液相色谱-质谱 (LC-MS) 分析研究了枇杷果实响应热应激的激素变化。鉴定了几种有区别的激素代谢物，包括十四种细胞分裂素（CK）、八种生长素、五种茉莉酸（JA）、三种赤霉素酸（GA）、两种脱落酸（ABA）、两种水杨酸（SA）、一种乙烯（ETH）和一种独脚金内酯（SL）。转录组学分析表明，富含“植物激素信号转导”、“内质网蛋白质加工”、“光合作用”、“植物-病原体相互作用”和“氧化磷酸化”途径的基因参与了热应激反应。此外，小 RNA 分析进一步揭示了 miRNA，包括 “内质网中的蛋白质加工”、“光合作用”、“植物-病原体相互作用”和“氧化磷酸化”途径都参与了热应激反应。此外，小 RNA 分析进一步揭示了 miRNA，包括 “内质网中的蛋白质加工”、“光合作用”、“植物-病原体相互作用”和“氧化磷酸化”途径都参与了热应激反应。此外，小 RNA 分析进一步揭示了 miRNA，包括miRNA160-x、miRNA393-x、miR6187-x、miR8726-y和new-m0057-5p可能与生长素信号传导和热休克蛋白共同作用以调节热应激反应过程中的基因。总之，这项研究提供了对枇杷果实热应激反应背后复杂分子机制的全面理解。