LAUSR

Abstract The sugar content and sweetness are two indices used to characterize fruit quality in horticultural production. However, the regulation of sugar synthesis and the functional involvement of sugar signaling are far from clear. Here we descripted a strawberry S1 group basic leucine zipper (bZIP) factor FabZIPs1.1, which was significantly repressed by both blue and red light at the transcriptional level. The gene was expressed extensively in both vegetative and reproductive organs. It had closest phylogenetic relationship to AtbZIP53, with three putative sucrose-controlled upstream open reading frames (sc-uORF) in the 5′-leader region. The transcriptional level of FabZIPs1.1 was not affected by sucrose under in vitro conditions. The sucrose-induced repression of translation (SIRT) effect of FabZIPs1.1 was confirmed using stable transgenic Arabidopsis lines with a 35S::FabZIPs1.1-5′-leader-GUS reporter construct. Glucose can also induce translational inhibition of FabZIPs1.1, and this effect was sensitive to light. Transient over-expression of FabZIPs1.1 lacking the leader sequence can enhance sucrose accumulation in strawberry fruits. Our results revealed the sugar sensing and regulation role of FabZIPs1.1 and highlighted the involvement of environmental factors such as light in this mediation process.