马铃薯糖苷生物碱对腐皮镰刀菌呼吸作用及其活性氧代谢的影响

Potato glycoalkaloids affect the respiration and reactive oxygen species metabolism of Fusarium solani

摘要:

【背景】腐皮镰刀菌(Fusarium solani)是一种分布较为广泛的致病性真菌，可引起多种植物的土传病害，是枸杞根腐病的主要致病菌之一。马铃薯糖苷生物碱(potato glycoside alkaloids, PGA)为一类植物源提取物，其原材料种植广泛、成本低廉，对腐皮镰刀菌具有较强的抑菌活性。【目的】探究PGA对腐皮镰刀菌呼吸作用及活性氧(reactive oxygen species, ROS)代谢的影响，从能量代谢角度揭示其可能的抑菌机理。【方法】以马铃薯芽为原材料，采用乙酸-氨水沉淀法提取PGA，以腐皮镰刀菌为供试病原菌，通过PDA和PDB培养体系考察PGA对腐皮镰刀菌菌丝生长的抑制作用，并确定半最大效应浓度(EC₅₀)；采用氧电极仪检测PGA对腐皮镰刀菌呼吸作用的影响；并通过PDB液态培养试验体系，研究PGA对腐皮镰刀菌抗氧化酶系统、ROS及其代谢产物丙二醛(malondialdehyde, MDA)的影响。【结果】PGA处理下菌丝体呼吸速率明显下降，且随着PGA处理时间的延长，表现出一定的时间浓度效应。PGA处理使胞内过氧化氢(H₂O₂)和超氧阴离子(O₂⁻)含量显著增高(P<0.05)，引起了细胞体内过氧化物酶(peroxidase, POD)、过氧化氢酶(catalase, CAT)和超氧化物歧化酶(superoxide dismutase, SOD)抗氧化酶系统的失衡，加剧了膜脂过氧化进程，导致MDA含量增加。透射电镜结果显示，PGA处理的腐皮镰刀菌线粒体膜组织破裂，线粒体内含物逐渐流失，线粒体消亡。【结论】PGA抑制了腐皮镰刀菌呼吸作用及活性氧代谢，破坏了其能量代谢途径的主要细胞器——线粒体，最终抑制了病原菌菌丝的生长。

Abstract:

[Background] Fusarium solani, a ubiquitous pathogenic fungus, can cause a variety of soil borne diseases of plants and is one of the main pathogens causing root rot of Lycium barbarum. Potato glycoalkaloids (PGAs) have strong activity against F. solani and their source plants are widely cultivated with low cost. [Objective] To observe the effects of PGAs on the respiration and reactive oxygen species (ROS) metabolism of F. solani and decipher the possible antibacterial mechanism from the perspective of energy metabolism. [Methods] PGAs were extracted from potato buds by acetic acid and ammonia precipitation method, and F. solani was selected as the test pathogen. The inhibitory effect of PGAs on the mycelial growth of F. solani in PDA and PDB was investigated and the concentration for 50% of maximum effect (EC₅₀) was determined. The effect of PGAs on the respiration of F. solani was detected by an oxygen electrode. The effects of PGAs on the antioxidant enzyme system, ROS, and the metabolite malondialdehyde (MDA) of F. solani were studied in PDB. [Results] The PGA treatment decreased the mycelial respiration rate in a concentration and time-dependent manner and increased the content of intracellular hydrogen peroxide (H₂O₂) and superoxide anion (O₂⁻) (P<0.05). Furthermore, the treatment caused the imbalance of the peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) system, aggravated the membrane lipid peroxidation, and increased MDA content. Transmission electron microscopy results showed that the PGA treatment broke the mitochondrial membrane, caused the loss of mitochondrial contents, and destroyed the mitochondria of F. solani. [Conclusion] PGAs inhibit the respiration and reactive oxygen species metabolism, destroy mitochondria, the main organelle of the energy metabolism pathway, and finally inhibit the mycelial growth of F. solani.