Carotenoid-carbohydrate crosstalk: evidence for genetic and physiological interactions in storage tissues across crop species

Authors: VILLWOCK, SEREN - Cornell University; Li, Li; Jannink, Jean Luc

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2024
Publication Date: 10/14/2024
Citation: Villwock, S.S., Li, L., Jannink, J. 2024. Carotenoid-carbohydrate crosstalk: evidence for genetic and physiological interactions in storage tissues across crop species. New Phytologist. 244:1709-1722. https://doi.org/10.1111/nph.20196.
DOI: https://doi.org/10.1111/nph.20196

Interpretive Summary: This review looks at how carotenoids (plant pigments important for photosynthesis and nutrition) interact with carbohydrates like sugars and starches in crops. While breeding has successfully increased carotenoid levels in many staple foods, it has sometimes caused unwanted changes, such as less starch or different sugar levels. Research in crops like cassava, sweet potato, and maize shows that higher carotenoids often mean less starch but more sugars. Scientists think this link could be due to competition for the same building blocks, changes inside plant cell structures where both are made, or signals from sugars and carotenoid by-products affecting each other’s production. Some of these links may also be due to genetics or statistical effects, not biology. Understanding these interactions could help breeders develop nutrient-rich crops without hurting other important qualities like dry matter content.

Technical Abstract: Carotenoids play essential roles in photosynthesis, photoprotection, and human health. Efforts to increase carotenoid content in several staple crops have been successful through both conventional selection and genetic engineering methods. Interestingly, in some cases, altering carotenoid content has had unexpected effects on other aspects of plant metabolism, impacting traits like sugar content, dry matter percentage, fatty acid content, stress tolerance, and phytohormone concentrations. Studies across several diverse crop species have identified negative correlations between carotenoid and starch contents, as well as positive correlations between carotenoids and soluble sugars. Collectively, these reports suggest a metabolic interaction between carotenoids and carbohydrates. We synthesize evidence pointing to four hypothesized mechanisms: (1) direct competition for precursors; (2) physical interactions in plastids; (3) influences of sugar or apocarotenoid signaling networks; and (4) nonmechanistic population or statistical sources of correlations. Though the carotenoid biosynthesis pathway is well understood, the regulation and interactions of carotenoids, especially in nonphotosynthetic tissues, remain unclear. This topic represents an underexplored interplay between primary and secondary metabolism where further research is needed.