The Endophytic Fungus Phomopsis liquidambari Increases Nodulation and N 2 Fixation in Arachis hypogaea by Enhancing Hydrogen Peroxide and Nitric Oxide Signalling

• Published in: Microbial ecology 2017-08, Vol.74 (2), p.427
• Main Authors: Xie, Xing-Guang, Fu, Wan-Qiu, Zhang, Feng-Min, Shi, Xiao-Min, Zeng, Ying-Ting, Li, Hui, Zhang, Wei, Dai, Chuan-Chao
• Format: Article
• Language: English
• Subjects: Arachis - microbiology; Ascomycota - physiology; Endophytes - physiology; Hydrogen Peroxide - metabolism; Nitric Oxide - metabolism; Nitrogen Fixation; Plant Root Nodulation; Symbiosis
• ISSN: 1432-184X
• DOI: 10.1007/s00248-017-0944-8

The continuous cropping obstacles in monoculture fields are a major production constraint for peanuts. Application of the endophytic fungus Phomopsis liquidambari has increased peanut yields, and nodulation and N fixation increases have been considered as important factors for P. liquidambari infection-improved peanut yield. However, the mechanisms involved in this process remain unknown. This work showed that compared with only Bradyrhizobium inoculation, co-inoculation with P. liquidambari significantly elevated endogenous H O and NO levels in peanut roots. Pre-treatment of seedlings with specific scavengers of H O (CAT) and NO (cPTIO) blocked P. liquidambari-induced nodulation and N fixation. CAT not only suppressed the P. liquidambari-induced nodulation and N fixation, but also suppressed the enhanced H O and NO generation. Nevertheless, the cPTIO did not significantly inhibit the induced H O biosynthesis, implying that H O acted upstream of NO production. These results were confirmed by observations that exogenous H O and sodium nitroprusside (SNP) reversed the inhibition of P. liquidambari-increased nodulation and N fixation by the specific scavengers. The transcriptional activities of the symbiosis-related genes SymRK and CCaMK of peanut-Bradyrhizobium interactions also increased significantly in response to P. liquidambari, H O and SNP treatments. The pot experiment further confirmed that the P. liquidambari infection-enhanced H O and NO signalling pathways were significantly related to the increase in peanut nodulation and N fixation. This is the first report that endophytic fungus P. liquidambari can increase peanut-Bradyrhizobium interactions via enhanced H O /NO-dependent signalling crosstalk, which is conducive to the alleviation of continuous cropping obstacles via an increase in nodulation and N fixation.