ROS regulate pollen germination and tube growth in Betula platyphylla with involvement of H2O2 and polyamine oxidase BpPAO2.

Abstract

Reactive oxygen species (ROS) function as important signaling molecules during pollen germination and pollen tube growth, however, the mechanisms coordinating ROS production in Betula platyphylla pollen tubes remain unclear. In this study, we combined fluoresence imaging, ROS scavengers treatments, transcriptome analysis, and antisence oligonucleotide-mediated knock down to investigate ROS dynamics and their regulatory basis during birch pollen tube development. ROS signals were detected in pollen grains and became enriched at the tips of elongating pollen tubes. Scavenging of O₂ ^·- significantly reduced tip-localized ROS accumulation, and impaired pollen germination and tube elongation. This indicating that balanced ROS production is required for normal pollen tube growth. To find the key regulator of ROS, we performed RNA-Seq for three stages of birch pollen tube development. Weighted gene co-expression network analysis (WGCNA) identified a ROS-enriched module highly associated with pollen tube growth, incorporating oxidoreductase genes distributed across mitochondria, chloroplasts, peroxisomes, endoplasmic reticulum, cytoplasm, and the apoplast. qRT-PCR validation confirmed coordinated activation of multiple ROS-related genes. Among these, the expression level of BpPAO2 which encoding a polyamine oxidase shows progressively increasing during three stages. Targeted inhibition of BpPAO2 through antisense oligonucleotides significantly decreased its transcript level and PAO activity, diminished H₂O₂ accumulation in the pollen tube, and strongly disrupted pollen germination and tube elongation. Our findings establish BpPAO2-mediated H₂O₂ production as a key regulator of pollen tube growth in B. platyphylla.

Supplementary information: The online version contains supplementary material available at 10.1007/s12298-026-01788-2.