Development of a FungalBraid Penicillium expansum-based expression system for the production of antifungal proteins in fungal biofactories

Fungal antifungal proteins (AFPs) have attracted attention as novel biofungicides. Their exploitation requires safe and cost-effective producing biofactories. Previously, Penicillium chrysogenum and Penicillium digitatum produced recombinant AFPs with the use of a P. chrysogenum-based expression system that consisted of the paf gene promoter, signal peptide (SP)-pro sequence and terminator. Here, the regulatory elements of the afpA gene encoding the highly produced PeAfpA from Penicillium expansum were developed as an expression system for AFP production through the FungalBraid platform. The afpA cassette was tested to produce PeAfpA and P. digitatum PdAfpB in P. chrysogenum and P. digitatum, and its efficiency was compared to that of the paf cassette. Recombinant PeAfpA production was only achieved using the afpA cassette, being P. chrysogenum a more efficient biofactory than P. digitatum. Conversely, P. chrysogenum only produced PdAfpB under the control of the paf cassette. In P. digitatum, both expression systems allowed PdAfpB production, with the paf cassette resulting in higher protein yields. Interestingly, these results did not correlate with the performance of both promoters in a luciferase reporter system. In conclusion, AFP production is a complex outcome that depends on the regulatory sequences driving afp expression, the fungal biofactory and the AFP sequence.This work was supported by grant RTI2018-101115B-C21 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”, PROMETEO/2018/066 from ‘Conselleria d’Educació’ (Generalitat Valenciana, Comunitat Valenciana, Spain) and by grant PCI2018-092893 funded by MCIN/AEI/ 10.13039/501100011033 and by “The European Union” (SUSPHIRE Project, ERACoBioTech; Horizon 2020 grant agreement No. 722361). EM and MGL were recipients of predoctoral grants FPU18/02019 and FPU19/02066 funded by MCIN/AEI/ 10.13039/501100011033 and by “ESF Investing in your future”.Peer reviewe