Effects Of Inoculated By Fusarium Oxysporum On LOX Activity And CmLOXs Expressions Of Melon (Cucumis Melo Var. Makuwa Makino)

At present, there are widely reports about lipoxygenases which play a role in adversity stress in domestic and foreign researches, but the stress response and mechanisms about the lipoxygenase of melon in adversity are seldom reported. The oriental melon cultivar ’Yumeiren’and’Caihong7’were used as the experimental materials and inoculated with Fusarium oxysporum at the period of three leaves. Then the relative conductivity, root vigor, MDA content, disease index, Fv/Fm, LOX activity and real-time fluorescent quantitative PCR analyses of CmLOXs genes expressions were determined in different days after inoculation. The effects of lipoxygenases gene family members(CmLOXs) in the oriental melon responding to Fusarium oxysporum f. sp. melonis were studied. The results were described as follow:1.’Yumeiren’ and ’Caihong7’ were used as the study materials. Then the various physiological indexes including relative conductivity, root vigor, MDA content, disease index and Fv/Fm in different oriental melon cultivars were determined. The results show that the relative conductivities, MDA contents and disease indexes of melon seedlings after inoculation increase, while root vigors and Fv/Fm decrease.2. Through the analyses of LOX activity in melon leaves and roots, the results show that the LOX activity in’Yumeiren’is higher than’Caihong7’and melon roots is higher than melon leaves. After spraying NDGA which is a LOX inhibitor, the activity of LOX decrease and the damage degrees of melon seedlings are higher than only inoculated with Fusarium oxysporum plants. It is speculated that LOX activity and defense against pathogens infection have certain relations, but the mechanism that jasmonic acid produced through LOX pathway play a role in defense reactions remains to be further research.3. There were 13 CmLOXs up-regulated in leaves after inoculating with Fusarium oxysporum f. sp. Melonis. Among them, the expression of CmLOX02 and CmLOX11 were significantly increased at 3 day after inoculation, while other 11 CmLOXs (CmLOX03, CmLOX07-10, CmLOX12-17) reached peak value at 5 day.4. Meanwhile, there were 5 CmLOXs up-regulated in roots after inoculation. CmLOX03, CmLOX16 and CmLOX17 were significantly increased at 1 day after inoculation, while CmLOX05 and CmLOX06 were significantly higher than the control at 3 day.5. After spraying NDGA to the leaves of melon seedlings, the expression of CmLOX03、 CmLOX10 and CmLOX12 decreased. Furthermore, the expression of CmLOX03、CmLOX17 in melon root decreased following spraying NDGA. The experiment results provide the theoretical basis for the future study in the role of LOXs in pathogen infection.In summary, the leaves and roots of oriental melon suffered with more or less infection, following inoculating with Fusarium oxysporum f. sp. Melonis. The change tendencies of the LOX activity increase was positively correlated with relative conductivity, MDA content, while negatively correlated with root activity. Meanwhile, the disease index increased and fluorescence parameters declined. Furthermore, CmLOXs expressions in leaves and roots of melon exist obvious space-time difference. CmLOX03、CmLOX12、CmLOX18 expression in melon leaves significantly increased after inoculating with Fusarium oxysporum f. sp. Melonis, while CmLOX03、CmLOX06、CmLOX16 expression quantity change significantly in melon roots. These results of this experiment suggest that CmLOXs may participate in defense responses against pathogens and the study will provide the foundation for subsequent research in which the founction of LOX under the biotic stress were identified through transgenic technology.