Abstract

10 ºC low temperature alleviates IB in pineapple by reducing total phenolics level. • Low temperature-repressible AcWRKY75 is strongly related to total phenolics. • AcWRKY75 directly activates the transcription of Ac4CL5 , AcC4H5 , and AcHCT4. • Upregulating AcWRKY75 in pineapple increased total phenolics and IB severity. Harvested pineapple ( Ananas comosus L.) fruit is highly susceptible to internal browning (IB), which causes quality deterioration and economic loss. Low-temperature storage effectively suppresses IB development; however, the underlying molecular mechanisms remain incompletely understood. In this study, fruit stored at 10 °C exhibited milder IB compared with fruit stored at 25 °C, and showed reduced total phenolics together with higher retention of soluble sugars and soluble protein. Correlation analysis indicated a significant association between total phenolics and IB severity. Weighted gene co-expression network analysis (WGCNA) based on differentially expressed genes and total phenolics identified AcWRKY75 as a transcription activator strongly correlated with IB and total phenolics. The transcription levels of AcWRKY75 and phenylpropanoid pathway genes, including Ac4CL5 , AcC4H5 , and AcHCT4 , were coordinately suppressed during storage at 10 °C. The promoters of Ac4CL5 , AcC4H5 , and AcHCT4 were directly bound and activated by AcWRKY75. Transient overexpression of AcWRKY75 in pineapple pulp further confirmed that elevated AcWRKY75 expression enhanced the transcription levels of these genes, increased total phenolics and promoted IB. These findings demonstrate that AcWRKY75 positively regulates IB by promoting total phenolics accumulation through activation of phenylpropanoid pathway genes, and that low-temperature storage mitigates IB partly by repressing AcWRKY75 expression. This work advances understanding of the transcriptional regulatory mechanisms underlying IB alleviation in pineapple fruit stored at low temperature and prov