CSIC develops a technique that multiplies the beta-carotene content in plant leaves

A research group from the Institute of Molecular and Cellular Plant Biology (IBMCP), a joint center of the Spanish National Research Council (CSIC) and the Polytechnic University of Valencia (UPV), has developed an innovative method for the biofortification of leaves and other green plant tissues by increasing their content of healthy substances such as beta-carotene, the main precursor of vitamin A in the human diet. The study demonstrates that, through biotechnological techniques and high-intensity light treatments, it is possible to multiply beta-carotene levels in leaves by up to 30 times by creating new storage sites for it, without affecting vital processes such as photosynthesis. The results are published in the journal Plant Journal.

Beta-carotene is one of the main carotenoids, pigments that are naturally found in plants and other photosynthetic organisms and are beneficial for health, with antioxidant, immune-stimulating, and cognitive-enhancing properties. Specifically, beta-carotene is the primary precursor of retinoids, chemical compounds with important functions in the body (vision, cell proliferation and differentiation, immune system...), including vitamin A.

Using tobacco plants (Nicotiana benthamiana) as a laboratory model and lettuce (Lactuca sativa) as a cultivation model, the team led by Manuel Rodríguez Concepción, a CSIC research professor at IBMCP, has succeeded in increasing the beta-carotene content in the leaves without negatively affecting other vital processes such as photosynthesis.

Rodríguez sums up:

"Leaves require carotenoids such as beta-carotene in the photosynthetic complexes of chloroplasts for proper functioning. When too much or too little beta-carotene is produced in the chloroplasts, they stop functioning, and the leaves eventually die. Our work has successfully produced and accumulated beta-carotene in cellular compartments where it is not usually found by combining biotechnological techniques and high-intensity light treatments".

Better accumulation and bioaccessibility

The results of this study, published in the Plant Journal, demonstrate that it is possible to multiply the levels of beta-carotene in leaves by creating new storage sites outside the photosynthetic complexes.

On one hand, they have managed to store high levels of beta-carotene in plastoglobules, fat storage vesicles naturally present within chloroplasts. These vesicles do not participate in photosynthesis and do not normally accumulate carotenoids.

The first author of the study, Luca Morelli, states:

"By stimulating the formation and development of plastoglobules with molecular techniques and intense light treatments, not only can beta-carotene accumulation be increased, but also its bioaccessibility, meaning the ease with which it can be extracted from the food matrix to be absorbed by our digestive system".

Biofortification of produce

On the other hand, the study demonstrates that the synthesis of beta-carotene in plastoglobules can be combined with its production outside the chloroplasts through biotechnological approaches.

Pablo Pérez Colao, co-author of the study, comments:

"Beta-carotene accumulates in vesicles similar to plastoglobules but located in the cytosol, the watery substance that surrounds the organelles and the nucleus of the cells".

The combination of both strategies achieved up to a 30-fold increase in accessible beta-carotene levels compared to untreated leaves. The massive accumulation of beta-carotene also gave the lettuce leaves a distinct golden coloration.

In the researchers' opinion, the discovery that beta-carotene can be produced and stored at very high levels and in a more bioaccessible form outside of its usual locations in the leaves "represents a significant breakthrough for improving nutrition through the biofortification of vegetables like lettuce, Swiss chard, or spinach, without sacrificing their characteristic aroma and flavor".

Reference:

Morelli L, Perez-Colao P, Reig-Lopez D, Di X, Llorente B, Rodriguez-Concepcion M. Boosting pro-vitamin A content and bioaccessibility in leaves by combining engineered biosynthesis and storage pathways with high-light treatments. Plant J. 2024.

DOI: https://doi.org/10.1111/tpj.16964