New insights into the regulatory effects of galloylated catechin on male reproduction in Camellia oleifera.

Flavonoids, particularly galloylated catechins, are known to regulate pollen tube growth, but their mode of action in woody plants remains poorly characterized. Here, we investigated the effects of epigallocatechin gallate (EGCG)-a major galloylated catechin-on Camellia oleifera pollen tubes using combined cytological and transcriptomic approaches. In vitro treatment with 100 μg mL-1 EGCG significantly reduced pollen germination and tube elongation. Confocal and fluorescence microscopy revealed that EGCG rapidly disrupted the apical Ca2+ gradient within 10 min, accompanied by disorganized actin filaments and altered distribution of methyl-esterified pectin at the tube apex. Transcriptome profiling and antisense oligonucleotide (AS-ODN)-mediated knockdown identified a Rho GTPase-activating protein (ROPGAP6)-centered regulatory network associated with growth inhibition. Weighted gene co-expression network analysis and subsequent AS-ODN knockdown experiments further revealed transcriptional coordination among Decapping protein 1 (Dcp1), small heat shock factor (sHSF) and ROPGAP6 in response to EGCG treatment. Collectively, our findings offer a multilevel framework for understanding how galloylated catechins regulate pollen tube growth in C. oleifera, providing insights into their roles in male reproduction of trees.