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Specialized metabolites are structurally diverse and cell‐ or tissue‐specific molecules produced in restricted plant lineages. In contrast, primary metabolic pathways are highly conserved in plants and produce metabolites essential for all of life, such as amino acids and nucleotides. Substrate promiscuity – the capacity to accept non‐native substrates – is a common characteristic of enzymes, and its impact is especially apparent in generating specialized metabolite variation. However, promiscuity only leads to metabolic diversity when alternative substrates are available; thus, enzyme cellular and subcellular localization directly influence chemical phenotypes. We review a variety of mechanisms that modulate substrate availability for promiscuous plant enzymes. We focus on examples where evolution led to modification of the ‘cellular context’ through changes in cell‐type expression, subcellular relocalization, pathway sequestration, and cellular mixing via tissue damage. These varied mechanisms contributed to the emergence of structurally diverse plant specialized metabolites and inform future metabolic engineering approaches.
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Is specialized metabolite regulation specialized?
Abstract Recent technical and theoretical advances have generated an explosion in the identification of specialized metabolite pathways. In comparison, our understanding of how these pathways are regulated is relatively lagging. This and the relatively young age of specialized metabolite pathways has partly contributed to a default and common paradigm whereby specialized metabolite regulation is theorized as relatively simple with a few key transcription factors and the compounds are non-regulatory end-products. In contrast, studies into model specialized metabolites, such as glucosinolates, are beginning to identify a new understanding whereby specialized metabolites are highly integrated into the plants’ core metabolic, physiological, and developmental pathways. This model includes a greatly extended compendium of transcription factors controlling the pathway, key transcription factors that co-evolve with the pathway and simultaneously control core metabolic and developmental components, and finally the compounds themselves evolve regulatory connections to integrate into the plants signaling machinery. In this review, these concepts are illustrated using studies in the glucosinolate pathway within the Brassicales. This suggests that the broader community needs to reconsider how they do or do not integrate specialized metabolism into the regulatory network of their study species.
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- PAR ID:
- 10462447
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Experimental Botany
- Volume:
- 74
- Issue:
- 17
- ISSN:
- 0022-0957
- Format(s):
- Medium: X Size: p. 4942-4948
- Size(s):
- p. 4942-4948
- Sponsoring Org:
- National Science Foundation
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