Chromosome-level genome assembly of Tilia mandshurica reveals divergence of duplicated TPP genes associated with fructose-rich nectar formation.

Authors

Lin Lin, Jiayi Du, Qingshan Li, Cong Yu, Le Chen, Wenzheng Li, Fucai Xia, Huaizhi Mu

Published in

Tree physiology. Oct 09, 2026. Epub Oct 09, 2026.

Abstract

Tilia mandshurica is an important woody nectar plant, but the genomic and transcriptional basis of its nectar sugar accumulation remains poorly understood. Here, we generated a chromosome-level reference genome for T. mandshurica and integrated comparative genomics, gene duplication analysis, RNA-seq across seven floral developmental stages, qRT-PCR validation, carbohydrate measurements and metabolite profiling. Gene family analysis revealed lineage-specific expansion of families involved in carbohydrate metabolism, ion transport and specialized metabolism. Ks and synteny analyses identified an ancient Eocene whole-genome duplication likely shared with Craigia yunnanensis, whereas duplication-mode analysis indicated that subsequent small-scale duplications contributed to lineage-specific duplicate retention. Among the enriched carbohydrate-related categories, trehalose-phosphatase activity provided a link between genome evolution and floral sugar accumulation. Sixteen trehalose-phosphate phosphatase (TPP) genes separated into fructose-positive C1 and fructose-negative C2 classes, with strong divergence at both the gene level (Δ = 1.060) and module level (Δ = 1.294). C1 TPP genes tracked fructose accumulation, whereas C2 genes followed starch-related developmental programs. Coexpression analysis further revealed contrasting network architectures: C1 TPP genes formed a convergent network with enriched vacuolar/tonoplast-related targets, whereas C2 genes showed a dispersed architecture with no consensus targets. C1-co-expressed candidates included genes related to vacuolar ion homeostasis, cell-wall/glycan remodeling, and isoprenoid/carotenoid metabolism. Together, these results support a model in which duplicated TPP genes are associated with distinct carbohydrate-associated transcriptional programs for starch remobilization and fructose-rich nectar formation. This study provides a genomic resource for Tilia and identifies candidate TPP-centered networks for nectar sugar accumulation in woody honey plants.

PMID:
42853113
Bibliographic data and abstract were imported from PubMed on 09 Oct 2026.

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