Biotechnology Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Plant Resource Conservation and Germplasm Innovation, Southwest University, Chongqing, 400715, China; State Cultivation Base of Crop Stress Biology for Southern Mountainous Land, Academy of Agricultural Sciences, Southwest University, Chongqing, 400715, China.
Biotechnology Research Center, Southwest University, Chongqing, 400715, China; State Cultivation Base of Crop Stress Biology for Southern Mountainous Land, Academy of Agricultural Sciences, Southwest University, Chongqing, 400715, China.
Metab Eng. 2021 Nov;68:187-198. doi: 10.1016/j.ymben.2021.10.008. Epub 2021 Oct 18.
Herbicide-resistance in weeds has become a serious threat to agriculture across the world. Thus, there is an urgent need for the discovery and development of herbicides with new modes of action. Thaxtomin phytotoxins are a group of nitrated diketopiperazines produced by potato common scab-causing phytopathogen Streptomyces scabies and other actinobacterial pathogens. They are generally considered to function as inhibitors of cellulose synthesis in plants, and thus have great potential to be used as natural herbicides. Generation of an overproducing strain is crucial for the scale-up production of thaxtomins and their wide use in agriculture. In the present study, we employed a stepwise strategy by combining heterologous expression, repressor deletion, activator overexpression, and optimization of fermentation media for high-level production of thaxtomins. The maximum yield of 728 mg/L thaxtomins was achieved with engineered Streptomyces albidoflavus J1074 strains in shake-flask cultures, and it was approximately 36-fold higher than S. albidoflavus J1074 carrying the unmodified cluster. Moreover, the yield of thaxtomins could reach 1973 mg/L when the engineered strain was cultivated in a small-scale stirred-tank bioreactor. This is the highest titer reported to date, representing a significant leap forward for the scale-up production of thaxtomins. Our study presents a robust, easy-to-use system that will be broadly useful for improving titers of bioactive compounds in many Streptomyces species.
杂草的抗除草剂性已成为全世界农业的严重威胁。因此，迫切需要发现和开发具有新作用模式的除草剂。炭疽菌毒素植物毒素是一组由马铃薯普通疮痂病致病病原体链霉菌疮痂病和其他放线菌病原体产生的硝化二酮哌嗪。它们通常被认为是植物纤维素合成的抑制剂，因此具有很大的潜力作为天然除草剂。产生高产菌株对于炭疽菌毒素的规模化生产及其在农业中的广泛应用至关重要。在本研究中，我们采用了逐步策略，结合异源表达、抑制剂缺失、激活剂过表达和发酵培养基优化，实现了炭疽菌毒素的高水平生产。经过工程化的白色链霉菌 J1074 菌株在摇瓶培养中达到了 728mg/L 的炭疽菌毒素最大产量，比携带未修饰簇的白色链霉菌 J1074 高出约 36 倍。此外，当在小型搅拌罐生物反应器中培养工程菌株时，炭疽菌毒素的产量可达 1973mg/L。这是迄今为止报道的最高浓度，代表着炭疽菌毒素规模化生产的重大飞跃。我们的研究提出了一个强大、易于使用的系统，将广泛用于提高许多链霉菌物种中生物活性化合物的产量。
