LaHT6-mediated hexose supply regulates cellulose biosynthesis in senescent luffa fruit

Senescence in luffa ( Luffa acutangula (L.) Roxb.) fruit adversely affects its postharvest quality and shelf life. During senescence, fiber networks developed with increased cellulose but decreased soluble sugars. The development of its characteristic fibrous network requires substantial hexose supply. Understanding the role of hexose transporters ( LaHT s) in this process is crucial for improving storage technologies, yet remains limited. Here, 24 LaHT s were identified in the luffa genome. LaHT6 expression strongly correlated with sugar and cellulose content, and demonstrated fructose/glucose transport activity in yeast. mRNA in situ hybridization further confirmed its high accumulation in the fruit vascular bundles (FVB). Subsequently, silencing LaHT6 resulted in abnormal sugar accumulation, accompanied by reduced expression of LaCES1.1/LaCES3.1 and consequent decreases in UDPG and cellulose content, whereas overexpression yielded opposite effects. Furthermore, the transcription factor LaDOF3.7, upregulated during senescence, activates LaHT6 transcription. These results indicate that LaHT6 -mediated sugar transport regulates cellulose accumulation, providing functional insights into LaHT genes and revealing LaHT6 's role in luffa senescence.