ZHONG Siyu, JIAO Jiahui, ZHAO Le, YU Xincan, TANG Guanghui, LIANG Chaoqiong, LI Peiqin
Stem canker, caused by Fusarium zanthoxyli, is a devastating disease in prickly ash production. The limited understanding of pathogen-host interaction mechanisms has hindered the development of effective control strategies. Effector proteins, which are crucial in these interactions, offer key insights into pathogenic mechanisms. In this study, we focused on FzEP119, an effector protein gene previously identified to be significantly up-regulated during the early infection stage of F. zanthoxyli. We constructed a knockout mutant (ΔFzEP119) and a complemented strain (ΔFzEP119-C) to systematically analyze the function of this gene in the pathogenicity and biological characteristics of the fungus. The results showed that, compared to the wild-type strain (Fz-WT), the virulence of ΔFzEP119 was significantly reduced, with lesions only 37% the size of those caused by Fz-WT. Although ΔFzEP119 showed no significant differences in mycelial growth rate, sporulation, and spore germination rate compared to the wild-type, its germ tubes were significantly shorter. In terms of carbon source utilization, the mutant exhibited significantly faster colony growth than Fz-WT when maltose was used as the carbon source, but grew significantly slower on glucose. Regarding nitrogen source utilization, ΔFzEP119 grew significantly slower than the wild-type on yeast extract, beef extract, potassium nitrate, and sodium nitrate. Additionally, ΔFzEP119 exhibited significantly reduced tolerance to H2O2 stress, while its responses to Congo red and NaCl stresses were similar to those of the wild-type. The mycelial penetration ability of ΔFzEP119 was also markedly impaired. The complemented strain ΔFzEP119-C restored virulence and other related biological characteristics to wild-type levels. In conclusion, the effector protein FzEP119 is a positive regulator of virulence in F. zanthoxyli and is involved in regulating multiple physiological processes, including germ tube elongation, nutrient utilization, stress response, and hyphal penetration. This study lays a foundation for further elucidating the molecular function and mechanism of FzEP119.
