Abstract

Pericarp dehydration is a primary factor contributing to litchi fruit browning, severely limiting the marketability of the product. Aquaporins (AQPs), a class of multifunctional membrane proteins, play a pivotal role in regulating the transmembrane transport of water in plants. However, the specific involvement of AQPs in the dehydration and browning of litchi fruit, along with their underlying regulatory mechanisms, remain to be fully elucidated. The results of the present study demonstrated that control (unpackaged) litchi fruit exhibited complete browning, which was accompanied by severe weight loss (10.2 %), discoloration, and membrane damage after 60 h of storage. These rapid physiological changes were alleviated by the use of polyethylene bag packaging, an effective high-humidity maintenance method. Transcriptomic analysis revealed differential expression of 12 AQP genes across the experimental groups, among which four genes ( LcPIP1;1 , LcPIP2;2 , LcPIP2;5 and LcSIP2;1 ) were upregulated, while eight genes ( LcPIP2;7 , LcTIP1;2 , LcTIP2;1 , LcTIP4;1 , LcTIP1;1 , LcSIP2;2 , LcNIP1;1 and LcNIP1;2 ) were downregulated in control fruit during storage. The changes in the expression of most AQP genes observed in control fruit were substantially counteracted by packaging treatment, thereby ameliorating pericarp dehydration and browning in litchi fruit. Furthermore, LcMYB6, a MYB transcription factor that is induced by packaging treatment, binds to the promoters of LcPIP1;1 and LcPIP2;5 . Promoter binding assays verified that LcMYB6 is a nuclear protein that directly represses the transcription of LcPIP1;1 and LcPIP2;5. Transient silencing of LcMYB6 promoted the upregulation of LcPIP1;1 and LcPIP2;5 expression while accelerating pericarp dehydration and browning. These results indicate that LcMYB6 may increase litchi dehydration resistance by d