Transportation engineering for enhanced production of plant natural products in microbial cell factories

Abstract

Plant natural products (PNPs) exhibit a wide range of biological activities and have essential applications in various fields such as medicine, agriculture, and flavors. Given their natural limitations, the production of high-value PNPs using microbial cell factories has become an effective alternative in recent years. However, host metabolic burden caused by its massive accumulation has become one of the main challenges for efficient PNP production. Therefore, it is necessary to strengthen the transmembrane transport process of PNPs. This review introduces the discovery and mining of PNP transporters to directly mediate PNP transmembrane transportation both intracellularly and extracellularly. In addition to transporter engineering, this review also summarizes several auxiliary strategies (such as small molecules, environmental changes, and vesicles assisted transport) for strengthening PNP transportation. Finally, this review is concluded with the applications and future perspectives of transportation engineering in the construction and optimization of PNP microbial cell factories.

Keywords: Microbial cell factories; Plant natural products; Transportation engineering; Transporters.

Fig. 1

The structure of ABC transporters and MATE transporters in plants. (A) The structure of plant ABC transporters, featuring positively arranged two TMDs and two NBDs in MDR subfamily and MRP subfamily transporters. (B) The structure of plant ABC transporter PDR subfamily, displaying two TMDs and two NBDs arranged in reverse. (C) The structure of a small number of MRP subfamily transporters in plant ABC transporters, characterized by five α-helices at the N-terminal. (D) The structure of a typical plant MATE transporter. ABC: ATP binding cassette; MATE: multidrug and toxic compound extrusion; TMD: transmembrane domain; NBD: nucleotide-binding domain; MDR: multidrug resistance; MRP: multidrug resistance-associated protein; PDR: pleiotropic drug resistance.

Fig. 2

Intracellular and extracellular transport process of PNPs. The figure illustrates typical transport processes of PNPs in eukaryotic cells and sub-cellular organelles. Arrows indicate the direction of PNPs transfer. BUP1: BIA uptake permease; PDR5/11/12/15: pleiotropic drug resistance transporter 5/11/12/15; YOL075C: an endogenous ABC transporter of S. cerevisiae; CmMATE1: C. melo MATE transporter 1; ClMATE1: C. lanatus MATE transporter 1; QDR1/2: quinidine resistance transporter 1/2; SNQ2: sensitivity to 4-nitroquinoline-N-oxide transporter 2; ABC-G1: G. clavigera ABC transporter; AtDTX1: A. thaliana detoxification 1; BPT1: bile pigment transporter 1; AbPUP1: A. belladonna purine uptake permease-like transporter 1; NtJAT1: N. tabacum jasmonate-inducible alkaloid transporter 1; NtMATE2: N. tabacum MATE transporter 2; CsABCC2/4a: C. sativus stigma ABC transporter 2/4a.

Fig. 3

Strategies for identifying PNP transporters. (A) General processes for the mining of PNP transporters, involving the establishment of a suitable screening model and bioinformatics analysis to identify specific PNP transporters from different plant tissues. (B) Molecular docking strategies to identify the best transporter candidates for a specific substrate. (C) Transportom-wide engineering and high-throughput screening processes for identifying specific PNP transporters. (D) Transcriptomic analysis with or without exogenous supplementation of PNPs for the identification of candidate transporters. PDR5/11/12: pleiotropic drug resistance transporter 5/11/12; SNQ2: sensitivity to 4-nitroquinoline-N-oxide transporter 2.

Fig. 4

Small molecule and low temperature assisted PNP efflux. (A) Small molecule-assisted PNP efflux, demonstrating the addition of organic solvents or adsorptive polymers to the cell culture system. (B) Environmental changes, such as low temperature, for enhanced efflux of PNPs. (C) Vesicular transport of PNPs, showcasing the efflux of PNPs encapsulated in vesicles.