FUSCA3 (FUS3) is a member of B3-domain transcription factor family and master regulator of seed development. It has potential roles in hormone biosynthesis and signaling pathways and therefore plays diverse roles in plant life cycle, especially in seed germination, dormancy, embryo formation, seed and fruit development, and maturation. However, there is limited information about its functions in seed and fruit development of grapevine. In this study, we expressed VvFUS3 in tomato for its functional characterization. Overexpression of VvFUS3 in tomato led to a reduction in seed number and seed weight without affecting the fruit size. Histological analysis found that both cell expansion and cell division in transgenic seed and fruit pericarp have been affected. However, there were no obvious differences in pollen size, shape, and viability, suggesting that VvFUS3 affects seed development but not the pollen grains. Moreover, the expression of several genes with presumed roles in seed development and hormone signaling pathways was also influenced by VvFUS3. These results suggest that VvFUS3 is involved in hormonal signaling pathways that regulate seed number and size. In conclusion, our study provides novel preliminary information about the pivotal roles of VvFUS3 in seed and fruit development and these findings can potentially serve as a reference for molecular breeding of seedless grapes.

FUSCA3 (FUS3)是 B3 域转录因子家族的成员，是种子发育的主要调节因子。它在激素生物合成和信号通路中具有潜在作用，因此在植物生命周期中发挥着多种作用，特别是在种子萌发、休眠、胚胎形成、种子和果实发育以及成熟方面。然而，关于其在葡萄种子和果实发育中的作用的信息有限。在这项研究中，我们在番茄中表达了 VvFUS3的功能表征。VvFUS3的过表达在番茄中导致种子数量和种子重量减少而不影响果实大小。组织学分析发现转基因种子和果实果皮中的细胞扩增和细胞分裂都受到了影响。然而，花粉大小、形状和活力没有明显差异，这表明VvFUS3影响种子发育但不影响花粉粒。此外，在种子发育和激素信号通路中具有假定作用的几个基因的表达也受到VvFUS3的影响。这些结果表明，VvFUS3参与了调节种子数量和大小的激素信号通路。总之，我们的研究提供了关于VvFUS3的关键作用的新的初步信息在种子和果实发育方面，这些发现可能为无核葡萄的分子育种提供参考。