Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing, 401331, People's Republic of China.
Chongqing Engineering Research Center for Fungal Insecticide, Chongqing, 401331, People's Republic of China.
Appl Microbiol Biotechnol. 2023 Feb;107(4):1257-1268. doi: 10.1007/s00253-022-12355-6. Epub 2023 Jan 14.
Microcycle conidiation commonly exists in filamentous fungi and has great potential for mass production of mycoinsecticides. L-Arginine metabolism is essential for conidiation and conditional growth and virulence, but its role in microcycle conidiation has not been explored. Here, a unique putative arginase (MaAGA) was characterized in the entomopathogenic fungus Metarhizium acridum. Conidial germination and thermotolerance were facilitated by the disruption of MaAGA. Despite little impact on fungal growth and virulence, the disruption resulted in normal conidiation after a 60-h incubation on microcycle conidiation medium (SYA) under normal culture conditions. In the MaAGA-disruption mutant (ΔMaAGA), intracellular arginine accumulation was sharply increased. Replenishment of the direct metabolites of arginase, namely ornithine and/or urea, was unable to restore the disruption mutant's microcycle conidiation on SYA. Interestingly, nitric oxide synthase (NOS) activity and nitric oxide (NO) levels of the ΔMaAGA strain were markedly decreased in the 60-h-old SYA cultures. Finally, adding N-nitro-L-arginine, an inhibitor of NOS, into the SYA converted the microcycle conidiation of the wild-type strain to normal conidiation. In contrast, adding sodium nitroprusside, an NO donor, into the SYA recovered the mutant's microcycle conidiation. The results indicate that arginine metabolism controls microcycle conidiation by changing the content of NO. KEY POINTS: • The MaAGA-disruption led to normal conidiation on microcycle conidiation medium SYA. • Nitric oxide (NO) level of the ΔMaAGA strain was markedly decreased. • Adding an NO donor into the SYA recovered the microcycle conidiation of ΔMaAGA.
微周期分生通常存在于丝状真菌中，对于大量生产真菌杀虫剂具有巨大潜力。L-精氨酸代谢对分生和条件生长和毒力至关重要，但它在微周期分生中的作用尚未得到探索。在这里，在昆虫病原真菌玫烟色棒束孢中鉴定了一种独特的假定精氨酸酶（MaAGA）。MaAGA 缺失促进了分生孢子的萌发和耐热性。尽管对真菌生长和毒力几乎没有影响，但在正常培养条件下，在微周期分生培养基（SYA）上孵育 60 小时后，破坏会导致正常的分生。在 MaAGA 缺失突变体（ΔMaAGA）中，细胞内精氨酸积累急剧增加。补充精氨酸酶的直接代谢物，即鸟氨酸和/或尿素，无法恢复 ΔMaAGA 突变体在 SYA 上的微周期分生。有趣的是，ΔMaAGA 菌株的一氧化氮合酶（NOS）活性和一氧化氮（NO）水平在 60 小时的 SYA 培养物中明显降低。最后，将 N-硝基-L-精氨酸，NOS 的抑制剂，添加到 SYA 中，将野生型菌株的微周期分生转化为正常的分生。相比之下，将一氧化氮供体硝普钠添加到 SYA 中恢复了突变体的微周期分生。结果表明，精氨酸代谢通过改变 NO 的含量来控制微周期分生。要点：• MaAGA 缺失导致 SYA 微周期分生培养基上的正常分生。• ΔMaAGA 菌株的 NO 水平明显降低。• 将 NO 供体添加到 SYA 中恢复了 ΔMaAGA 的微周期分生。
