Abstract
Sugars are the primary products of photosynthesis and play an important role in plant growth and development. They contribute to sweetness and flavor of fleshy fruits and are pivotal to fruit quality, and their translocation and allocation are mainly dependent on sugar transporters. Genome-wide characterization of Satsuma mandarin identified eighteen SWEET family members that encode transporters which facilitate diffusion of sugar across cell membranes. Analysis of the expression profiles in tissues of mandarin fruit at different developmental stages showed that CitSWEET11d transcripts were significantly correlated with sucrose accumulation. Further studies indicated that overexpression of CitSWEET11d in citrus callus and tomato fruit showed a higher sucrose level compared to wild-type, suggesting that CitSWEET11d could enhance sucrose accumulation. In addition, we identified an ERF transcription factor CitERF16 by yeast one-hybrid screening assay which could directly bind to the DRE cis-element on the promoter of CitSWEET11d. Overexpression of CitERF16 in citrus callus significantly induced CitSWEET11d expression and elevated sucrose content, suggesting that CitERF16 acts as a positive regulator to promote sucrose accumulation via trans-activation of CitSWEET11d expression.
Highlights
Sugars are the primary products of photosynthesis and play an important role during plant growth and development as sources of carbon skeletons, osmolytes, signals, transport molecules, and transient energy storage (Chen et al, 2015b)
The results indicated that sucrose content showed a continuous increase during development, and the accumulation mainly occurred at the later stage (150 DAFB to 180 DAFB), which is consistent with the change of soluble solids content (Figure 2)
The transcript abundance of CitSWEET11d was consistent with the accumulation of sucrose, and the relative index was up to 0.93 (Figure 3; Supplementary Figure S4)
Summary
Sugars are the primary products of photosynthesis and play an important role during plant growth and development as sources of carbon skeletons, osmolytes, signals, transport molecules, and transient energy storage (Chen et al, 2015b). There have been numerous studies in which SWEET members were identified at the genome level (Chong et al, 2014; Li et al, 2017a; Guo et al, 2018), compared to their well-known functions in phloem loading and seed filling described above, the understanding about the roles of SWEET in fruit development and sugar accumulation remains limited. The specific mechanisms remain unclear and further exploration of the regulation of SWEETs is necessary to elucidate and understand the regulatory network governing production and activity of SWEETs. In the current study, eighteen SWEET members were identified in Satsuma mandarin based on genome-wide analysis, their expression profiles during fruit development were analyzed and the transcript level of CitSWEET11d was found to be highly positively correlated with sucrose accumulation. Our results enrich and broaden the regulatory network of manipulating SWEETs and provide new insights into the functional roles of SWEETs to contribute to fruit quality by mediating sucrose accumulation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
