PbrFEN-1 positively regulates pear pollen tube growth and is involved in the self-incompatibility response

S-RNase-mediated gametophytic self-incompatibility (GSI) prevents self‑fertilization by inhibiting the growth of self-pollen tubes, yet the contribution of DNA metabolism, particularly radiation sensitive 2 (RAD2) family nucleases, to this process remains largely unknown. In this study, 49 RAD2 family genes were identified across pear and eight other fruit crops and classified into four conserved subfamilies (XPG, FEN-1, EXO1, and SEND). Of these, six RAD2 members were identified in pear, among which only PbrFEN-1 was significantly downregulated in pollen tubes treated with self S-RNases compared to non-self S-RNases, Furthermore, overexpression of PbrFEN-1 was found to alleviate the toxic effect of self S-RNase, indicating its involvement in the GSI response. Notably, antisense oligonucleotide-mediated knockdown of PbrFEN-1 disrupted ROS homeostasis at the pollen tube tip, leading to reduced ROS levels and subsequent inhibition of pollen tube growth. In contrast, pollen magnetofection-mediated overexpression of PbrFEN-1 helped maintain ROS homeostasis at the pollen tube tip, which was associated with faster pollen tube growth. These results suggest that PbrFEN-1 positively regulates ROS levels at the tip of pollen tube to support pollen tube elongation. These findings extend the mechanistic understanding of S-RNase-mediated GSI to the level of DNA metabolism and genome stability, providing new insights into the molecular basis of pollen tube inhibition in Rosaceae species.