Secondary metabolites in plants: transport and self-tolerance mechanisms

This review was written in response to the author’s receipt of the JSBBA Award for Young Scientists in 2015.

Abstract

Plants produce a host of secondary metabolites with a wide range of biological activities, including potential toxicity to eukaryotic cells. Plants generally manage these compounds by transport to the apoplast or specific organelles such as the vacuole, or other self-tolerance mechanisms. For efficient production of such bioactive compounds in plants or microbes, transport and self-tolerance mechanisms should function cooperatively with the corresponding biosynthetic enzymes. Intensive studies have identified and characterized the proteins responsible for transport and self-tolerance. In particular, many transporters have been isolated and their physiological functions have been proposed. This review describes recent progress in studies of transport and self-tolerance and provides an updated inventory of transporters according to their substrates. Application of such knowledge to synthetic biology might enable efficient production of valuable secondary metabolites in the future.

Graphical abstract

Uses of tolerance and transport proteins for efficient production of valuable compounds in microorganisms.

Key words:

• secondary metabolites
• self-tolerance
• transporter
• transport engineering

Acknowledgments

I am very grateful to professor Kazufumi Yazaki (Kyoto University) for his continuous support and invaluable discussion. I sincerely thank professor Fumihiko Sato (Kyoto University) for his kind guidance and encouragement, and all my past and present co-workers and laboratory members for their help and discussion. I also acknowledge Dr Akifumi Sugiyama for critical reading and comments on the manuscript. I am grateful to the Japan Society for Bioscience, Biotechnology, and Agrochemistry for its presentation to me of the Award for the Encouragement of Young Scientists.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes

This review was written in response to the author’s receipt of the JSBBA Award for Young Scientists in 2015.

Abbreviations: ABC, ATP-binding cassette; GST, glutathione S-transferase; MATE, multidrug and toxic compound extrusion; MDR, multidrug resistance; MRP, multidrug-resistance associated protein; NBD, nucleotide binding domain; NRT, nitrate transporter; PDR, pleiotropic drug-resistance; PUP; purine permease; TMD, transmembrane domain.