Integrative Transcriptomic and Metabolomics Reveal Dynamic Differences in Pathogen Resistance Between Resistant and Susceptible Cultivars of Myrica rubra

Background: Twig blight (TB), caused by Pestalotiopsis -like species, induces twig dieback in Myrica rubra, leading to substantial economic losses in its production across China and posing a significant threat to M. rubra cultivation. To date, the immune response of M. rubra to Pestalotiopsis -like infections remains poorly understood. Results: In this study, full-length transcriptomics and untargeted metabolomics were employed to investigate the immune responses of resistant “Dingao” (DA) and susceptible “Dongkui” (DK) M. rubra cultivars to Pestalotiopsis pathogen infection at early (1DPI) and later (5DPI) stage. The main findings revealed that the resistant DA triggered a rapid and robust immune response at 1DPI, with 1,111 differentially expressed genes (DEGs), including 583 increased and 528 decreased. As the immune response progressed to 5DPI, the number of DEGs in DA was reduced to with 324 DEGs (114 upregulated and 210 downregulated). In contrast, the susceptible DK cultivar exhibited a weak and delayed defense response. At 1DPI only 99 DEGs (26 upregulated and 73 downregulated) in DK leaves; by 5DPI, a substantial shift occurred in DK samples, with 3,414 DEGs (2,141 upregulated and 1,273 downregulated), showing a late but massive defense response. In DA samples, WRKY, AP2/ERF transcription factors (TFs) were the most up-regulated TFs at the early immune response stage; by 5DPI, NAC and WRKY families became the most prominently expressed TFs. In DK, notable TF upregulation (including WRKY, MYB and AP2/ERF ) was only observed at 5DPI and there were not significantly expression changes at the early immune response stage. Untargeted metabolomics further revealed that DK exhibited 280 upregulated and 12 downregulated differentially accumulated metabolites (DMs) at 1DPI; 503 DMs upregulated and 166 downregulated DMs at 5DPI. In DA plants, 472 DMs were upregulated and 110 downregulated at 1DPI, whereas at 5DPI, 387 DMs were upregulated and 219 downregulated. Conclusions: Through a combined analysis of full-length transcriptomics and untargeted metabolomics, we revealed distinct molecular and metabolic responses between resistant “Dingao” (DA) and susceptible “Dongkui” (DK) M. rubra cultivars under TB stress.