Identification of SWEET transporters in Lilium davidii var. unicolor and the regulatory function of LhSWEET14 in Lilium hybrida during postharvest dehydration stress

Sugar transport regulated by SWEET genes plays a crucial role in plant growth, development, and stress responses. However, there is no published study on the SWEET gene family in lily ( Lilium hybrida ). In this study, 42 LdSWEET genes were identified from the reference genome of Lilium davidii var. unicolor , which were distributed across 11 chromosomes and grouped into four subgroups with the conserved MtN3_slv domain. Homologous sequences of these genes were verified in L. hybrida , transcriptome analysis and Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) results identified LhSWEET14 sustained upregulation in petals of L. hybrida under postharvest dehydration stress. Transient silencing of LhSWEET14 in L. hybrida petals (TRV2:: LhSWEET14 ) significantly enhanced tolerance to postharvest dehydration stress; the relative water content at 16 days under postharvest dehydration stress was higher than the control, and H₂O₂ content decreased, while petal sucrose content decreased, and fructose content increased. Overexpression exacerbated wilting and membrane damage. Heterologous expression of LhSWEET14 in Solanum lycopersicum resulted in more severe leaf wilting and decreased contents of major soluble sugars (sucrose, glucose, fructose) in leaves under drought treatment. Together, this study revealed that LhSWEET14 negatively regulated the response of L. hybrida to postharvest dehydration stress. The results provide a candidate genetic locus for elucidating LhSWEET functions and molecular breeding of lily cultivars with improved postharvest dehydration tolerance.