Xiao Kun, Fan Junmiao, Bi Xiaoyi, Tu Xiaoyu, Li Xinyu, Cao Minghao, Liu Zheng, Lin Anqi, Wang Chong, Xu Pengbo, Lian Hongli
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China.
College of Horticulture Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao 066004, China.
Plant Physiol. 2025 Mar 1;197(3). doi: 10.1093/plphys/kiaf043.
Sugar accumulation during fruit ripening is an essential physiological change that influences fruit quality. While NAC transcription factors are recognized for their role in modulating strawberry (Fragaria × ananassa) fruit ripening, their specific contributions to sugar accumulation have remained largely unexplored. This study identified FvNAC073, a NAC transcription factor, as a key regulator that not only exhibits a gradual increase in gene expression during fruit ripening but also enhances the accumulation of sucrose. Further investigation showed that FvNAC073 positively regulates the expression of sucrose-6-phosphate synthase 1 (FvSPS1), a gene associated with sucrose synthesis, and negatively regulates sucrose synthase 2 (FvSUS2), which is involved in sucrose breakdown, through direct promoter binding. Additionally, we uncovered that FvCMB1L, a MADS-box protein, exhibits high gene expression levels at the premature fruit stage and acts to repress FvSPS1 while activating FvSUS2, thus negatively affecting sucrose accumulation. Notably, we demonstrated a competitive interaction between FvNAC073 and FvCMB1L in binding to the promoters of FvSPS1 and FvSUS2, resulting in antagonistic regulation of these genes. This intricate dynamic between FvCMB1L and FvNAC073 elucidates a mechanism for balancing sugar content during strawberry fruit development. Our findings offer insights into the complex regulatory network governing sucrose accumulation in strawberries, highlighting the potential for targeted genetic interventions to enhance fruit quality.
果实成熟过程中的糖分积累是影响果实品质的重要生理变化。虽然NAC转录因子在调节草莓（Fragaria × ananassa）果实成熟中的作用已得到认可，但其对糖分积累的具体贡献在很大程度上仍未得到探索。本研究确定了一种NAC转录因子FvNAC073，它不仅在果实成熟过程中基因表达逐渐增加，还能促进蔗糖的积累。进一步研究表明，FvNAC073通过直接结合启动子，正向调节与蔗糖合成相关的基因蔗糖-6-磷酸合酶1（FvSPS1）的表达，并负向调节参与蔗糖分解的蔗糖合酶2（FvSUS2）。此外，我们发现一种MADS-box蛋白FvCMB1L在果实早熟阶段具有高基因表达水平，它通过抑制FvSPS1同时激活FvSUS2来发挥作用，从而对蔗糖积累产生负面影响。值得注意的是，我们证明了FvNAC073和FvCMB1L在结合FvSPS1和FvSUS2启动子方面存在竞争性相互作用，导致对这些基因的拮抗调节。FvCMB1L和FvNAC073之间这种复杂的动态关系阐明了草莓果实发育过程中糖分含量平衡的机制。我们的研究结果为草莓中蔗糖积累的复杂调控网络提供了见解，突出了通过靶向基因干预提高果实品质的潜力。
