Evolution and seed development responses of Nelumbo SWEET genes

• Published in: Scientia horticulturae Vol. 333; p. 113281
• Main Authors: Chen, Lin, Xin, Jia, Song, Heyun, Cheng, Wei, Yang, Mei, Yang, Dong, Sun, Heng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2024
• Subjects: Evolution; Lotus seed; Nelumbo; Sugar transporter; SWEET; Sugar transporter; Evolution; Nelumbo; SWEET; Lotus seed
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2024.113281

•Phylogenetic and evolutionary analysis of SWEET genes in 13 plant species.•Systematic identification and functional characterization of SWEET genes in lotus.•Lotus SWEET proteins were localized in the plasma membrane.•Transcriptional regulation and co-expression network analysis of NnSWEET genes.•NnSWEET14 positively regulates soluble sugar accumulation in lotus seeds.
The Sugars Will Eventually be Exported Transporter (SWEET) proteins are a group of sugar transporters that are present in various organisms and facilitate the flux of sugars across cell membranes. In this study, we identified SWEET proteins from 13 representative plant species and further classified them phylogenetically into four clades. Different rates of contraction and expansion of SWEET genes were observed among different species. Our focus was on the characteristics and biological functions of SWEET genes in the basal eudicot lotus. A total of 26 SWEET genes were identified in Nelumbo, including 14 NnSWEETs in N. nucifera and 12 NlSWEETs in N. lutea. The expansion of SWEET genes in Nelumbo was driven by tandem and segmental duplication events. Analysis of three-dimensional (3D) structures revealed that SWEET proteins typically consist of two 3-TM units (THB1 and THB2) and are attached via the center TM4. Subcellular localization assays demonstrated that the NnSWEET proteins were localized in the plasma membrane. The potential transcriptional regulation mechanisms were investigated by systematically scanning for binding transcription factor in the promoter regions of NnSWEET genes. Some NnSWEETs were found to be preferentially expressed during lotus seed development, and co-expression analysis revealed that certain NnSWEET genes were involved in sugar and starch metabolism. Moreover, transient overexpression of NnSWEET14 significantly increased the soluble sugar content in lotus seed. These findings not only lay the groundwork for functional characterization of SWEET genes in Nelumbo, but also provide valuable genetic resources for future improvement of lotus seed quality.