Genome-Wide Analysis of the PR1 Gene Family in Pinus massoniana Under Bursaphelenchus xylophilus Stress

Pathogenesis-related protein 1 (PR1) plays important roles in plant responses to both biotic and abiotic stresses; however, its role in mediating defense against pine wood nematode in Pinus massoniana remains unclear. In this study, a total of 63 PR1 family members were identified in P. massoniana using bioinformatics approaches and were named PmPR1-1 to PmPR1-63 based on their phylogenetic relationships. Phylogenetic analysis showed that these members were distributed among four of the six subfamilies. Most of the encoded proteins were hydrophilic, with lengths ranging from 131 to 406 amino acids. Their promoter regions contained multiple cis-acting elements associated with phytohormone signaling and stress responses, and some members formed gene clusters on chromosomes 2, 5, and 9. qRT-PCR (quantitative reverse transcription polymerase chain reaction) analysis showed that the clustered genes PmPR1-46, PmPR1-55, PmPR1-56, and PmPR1-61 were significantly upregulated in the early stage of pine wood nematode inoculation in both resistant and susceptible P. massoniana plants, with higher expression levels in resistant plants. Transient overexpression of PmPR1-61 increased SOD and PPO activities as well as proline content while decreasing CAT activity. These results suggest that the PmPR1 family may be involved in the defense response of P. massoniana against pine wood nematode. Among them, PmPR1-55, PmPR1-56, and PmPR1-61 represent candidate resistance genes worthy of further investigation and provide valuable gene resources for elucidating resistance mechanisms and supporting molecular breeding in P. massoniana.