Joint transcriptomic and metabolomic analyses of the mechanisms of Juniperus tibetica in response to Arceuthobium oxycedri

Abstract As a key species in China's ecologically fragile Sanjiangyuan region, Juniperus tibetica faces severe threats from Arceuthobium oxycedri. This study preliminarily identified the mistletoe species parasitizing Juniperus tibetica as Arceuthobium oxycedri. The results of physiological parameter measurements indicate that infection with Arceuthobium oxycedri significantly increased the activity of peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), cinnamaldehyde dehydrogenase (CAD), glutathione peroxidase (GSH-Px) , as well as the malondialdehyde (MDA) and proline (PRO) content in Juniperus tibetica. This suggests that, under Arceuthobium oxycedri infection, Juniperus tibetica resists the infection by scavenging reactive oxygen species, increasing lignin content and enhancing drought-related physiological indicators. Multi-omics analysis indicates that following infection by Arceuthobium oxycedri, the major enriched pathways in Juniperus tibetica associated with the Arceuthobium oxycedri invasion are all linked to drought stress defence. It is hypothesised that the growth and reproduction of Arceuthobium oxycedri require the uptake of large amounts of water from the host, its parasitism leads to an imbalance in the host’s water transport, thereby triggering drought-stress-related response mechanisms. These findings are consistent with the results of physiological parameter measurements. This study provides preliminary insights into the physiological and molecular mechanisms by which Juniperus tibetica responds to Arceuthobium oxycedri stress, offering a theoretical basis for the effective control of the occurrence and damage caused by Arceuthobium oxycedri.