Longan (Dimocarpus longan Lour.) is a commercially valuable tropical fruit crop that contains two antagonistic FLOWERING LOCUS T (FT) homologs involved in regulating flowering time. However, how these FT genes interact with flowering regulators FLOWERING LOCUS D (FD) and APETALA1 (AP1) remains unknown. Four flowering-related genes in longan, DlFT1, DlFT2, DlAP1 and DlFD, were successfully isolated. Expression profiling revealed that all four genes were expressed in leaves and buds across different stages of natural and KClO₃-induced floral bud differentiation. Functional characterization through heterologous overexpression in Arabidopsis thaliana showed that DlAP1 significantly promotes early flowering under long-day conditions and induced morphological changes in floral organs and leaves. In contrast, DlFD overexpression had no effect on flowering time. Subcellular localization assays revealed that DlFT1 and DlFT2 localized to both the nucleus and the plasma membrane, while DlAP1 and DlFD localized exclusively to the nucleus. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) analyses revealed a novel regulatory node: DlFT1 directly interacts with DlAP1, a finding that expands the classical FT-FD-AP1 flowering model. Additionally, DlFD interacts more strongly with DlFT1 than with DlFT2, whereas DlFT1 only interacts with DlAP1, but not DlFT2. These results demonstrate that DlFT1 promotes flowering not only via the conserved FD-dependent pathway but also through direct association with AP1. These findings advance our understanding of the regulatory mechanisms of flowering in longan and provide valuable insights into flowering pathways of perennial woody species.

Papaya (Carica papaya L.) is a widely cultivated tropical and subtropical fruit crop valued for its rich nutritional content, diverse food industry applications, and the medicinal use of papain. However, bitterness in papaya fruit, particularly in fibrous strands, negatively affects fruit quality and consumer acceptance; therefore, the development of papaya cultivars with stable and desirable quality is of great importance. To identify the bitter compounds in papaya fruit fibrous strands and elucidate the molecular mechanisms underlying their biosynthesis, we performed transcriptomic and metabolomic analyses of fibrous strands from two papaya cultivars at three developmental stages. We identified carpaine, dehydrocarpaine II, and their derivative alkaloids. Furthermore, we identified two key regulatory genes, CpNAC82 and CpHD-Zip ANT2, associated with alkaloid biosynthesis. Finally, using single-nucleus RNA sequencing technology, we constructed a comprehensive gene expression atlas of papaya fibrous strands and stems, successfully identifying multiple cell types, including epidermal cells, guard cells, parenchyma cells, and phloem cells. Epidermal and phloem cells serve as the primary sites of alkaloid metabolism in papaya. These findings provide new insights into the molecular mechanisms of bitterness in papaya’s fibrous strands and yield genomic resources for improving fruit quality in papaya.