FmRbohH Mediates ROS Generation and Enhances Pollen Tube Growth in Fraxinus mandshurica

Flowering plants require normal pollen germination and growth to be fertilized, but studies on the mechanism regulating pollen tube growth in Fraxinus mandshurica are limited. Here, we used transcriptomic data to study the oxidative phosphorylation pathway during pollen tube growth in Fraxinus mandshurica. Our study identified 8,734 differentially expressed genes during the stages S1 to S3 of pollen tube growth. Significant enrichment of the oxidative phosphorylation pathway, amino acid synthesis, protein processing in the ER, carbon metabolism, pyruvate metabolism, citrate cycle (TCA cycle), and glycolysis/gluconeogenesis were examined using the Kyoto Encyclopedia of Genes and Genomes, and 58 genes linked to ROS synthesis and scavenging during the S1–S3 stages were identified. Also, H2DCFDA staining confirmed ROS formation in the pollen and the pollen tubes, and treatment with copper (II) chloride (CuCl2) and diphenyleneiodonium (DPI) was shown to reduce ROS in the pollen tube. Reduction in ROS content caused decreased pollen germination and pollen tube length. Furthermore, FmRbohH (respiratory burst oxidase homolog H) expression was detected in the pollen and pollen tube, and an antisense oligodeoxynucleotide assay demonstrated reduced ROS and pollen tube growth in Fraxinus mandshurica. This study shed more light on the RbohH gene functions during pollen tube growth.