Palmieri Davide, Miccoli Cecilia, Notardonato Ivan, Avino Pasquale, Lima Giuseppe, De Curtis Filippo, Ianiri Giuseppe, Castoria Raffaello
Department of Agricultural, Environmental and Food Sciences, University of Molise, Campobasso, Italy.
Department of Agricultural and Forestry Sciences, University of Tuscia, Viterbo, Italy.
Front Microbiol. 2022 Aug 1;13:973670. doi: 10.3389/fmicb.2022.973670. eCollection 2022.
The active regulation of extracellular pH is critical for the virulence of fungal pathogens. is the causal agent of green-blue mold on stored pome fruits and during its infection process acidifies the host tissues by secreting organic acids. is also the main producer of patulin (PAT), a mycotoxin found in pome fruit-based products and that represents a serious health hazard for its potential carcinogenicity. While it is known that PAT biosynthesis in is regulated by nutritional factors such as carbon and nitrogen and by the pH, the mechanistic effects of biocontrol on PAT production by are not known. In this work, we assessed how optimal and suboptimal concentrations of the biocontrol agent (BCA) LS28 affect both extracellular pH and PAT biosynthesis in . In wounded apples, the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from infection, respectively, and reduced PAT contamination in both cases. However, the suboptimal concentration of the BCA increased the specific mycotoxigenic activity by . , the rate of PAT biosynthesis was strictly related to the extracellular pH, with the highest amount of PAT detected in the pH range 4-7, whereas only traces were detectable at pH 3. Moreover, both and in apple wounds the BCA counteracted the extracellular -driven acidification maintaining extracellular pH around 4, which is within the pH range that is optimal for PAT biosynthesis. Conversely, in the absence of LS28 the pathogen-driven acidification led to rapidly achieving acidic pH values (<3) that lie outside of the optimal pH range for PAT biosynthesis. Taken together, these results suggest that pH modulation by LS28 is important to counteract the host tissue acidification and, therefore, the virulence of . On the other hand, the buffering of -driven acidification provided by the BCA increases the specific rate of PAT biosynthesis through the extension of the time interval at which the pH value lies within the optimal range for PAT biosynthesis. Nevertheless, the antagonistic effect provided by the BCA greatly reduced the total amount of PAT.
细胞外pH的主动调节对于真菌病原体的毒力至关重要。 是贮藏梨果上青霉病的病原体，在其感染过程中通过分泌有机酸使宿主组织酸化。 也是棒曲霉素（PAT）的主要产生者，棒曲霉素是一种存在于梨果类产品中的霉菌毒素，因其潜在的致癌性对健康构成严重危害。虽然已知 中PAT的生物合成受碳、氮等营养因子以及pH的调节，但生物防治对 产生PAT的机制影响尚不清楚。在这项工作中，我们评估了生物防治剂（BCA）LS28的最佳和次最佳浓度如何影响 中的细胞外pH和PAT生物合成。在受伤的苹果中，BCA的最佳和次最佳浓度分别为免受 感染提供了几乎完全和部分保护，并在两种情况下都减少了PAT污染。然而，BCA的次最佳浓度使 的比产毒活性增加。 ，PAT的生物合成速率与细胞外pH严格相关，在pH 4 - 7范围内检测到的PAT量最高，而在pH 3时仅可检测到痕量。此外，在苹果伤口处， 和BCA都抵消了由 驱动的酸化，使细胞外pH维持在4左右，这处于PAT生物合成的最佳pH范围内。相反，在没有LS28的情况下，病原体驱动的酸化导致迅速达到酸性pH值（<3），该值超出了PAT生物合成的最佳pH范围。综上所述，这些结果表明LS28调节pH对于抵消宿主组织酸化从而对抗 的毒力很重要。另一方面，BCA提供的对 驱动酸化的缓冲通过延长pH值处于PAT生物合成最佳范围的时间间隔来增加PAT生物合成的比速率。然而，BCA提供的拮抗作用大大减少了PAT的总量。
