Transcriptome analysis and metabolic profilingreveal the key role of carotenoids in thepetal coloration of Liriodendron tulipifera[2]
The coloration of leaves and petals holds significant economic value in ornamental plants. Liriodendron tulipifera, a highly popular ornamental horticultural plant in North America, features an orange stripe at the base of its leaves. However, the regulatory mechanism responsible for this orange striping remains unclear. This study revealed that during the petal formation process, the petal stripes appear pale yellow when the bracts (modified leaves) have fully senesced or fallen off, while they become deep orange when the petals are fully expanded.
Metabolically, the key pigment responsible for the coloration of petal stripes is the specific local accumulation of γ-carotenoids. At the transcriptional level, there are two major rate-limiting enzymes in the carotenoid synthesis process: carotenoid isomerase (CRTISO) and ε-lycopene cyclase (ε-LCY). These two enzymes are primarily responsible for the accumulation of the specific orange pigments in the petal stripes.
In comparison to Chinese Liriodendron tulipifera, the primary reason for the formation of orange petal stripes in North American Liriodendron tulipifera is the specific expression of ε-LCY.
Gene Regulation in Petal Development
Development of zeaxanthin-rich tomato fruit throughgenetic manipulations of carotenoid biosynthesis[3]
Carotenoid Metabolic Engineering in Tomatoes for Enhanced Zeaxanthin Content
Zeaxanthin, an oxygen-containing carotenoid, is a lipophilic pigment found in tomatoes and is a dihydroxylated derivative of β-carotene. It is known for its potential health benefits, including the prevention of cardiovascular diseases and the mitigation of atherosclerosis.
In this study, two approaches were employed to increase zeaxanthin content in tomato varieties: transgenic metabolic engineering and conventional breeding methods.
In the conventional breeding approach, hybridization was carried out by crossing a Bsh mutant (lacking the CYCB enzyme responsible for zeaxanthin synthesis) with a high zeaxanthin-producing hp3 individual. The resulting double mutant, BSH/hp3, was then further crossed with a gs individual (containing the STAY-GREEN mutation), yielding a triple mutant. Lastly, this triple mutant was crossed with a high-pigment mutant hp2dg to generate a quadruple homozygous mutant designated as "Xantomato." Throughout these successive crosses, the accumulation of zeaxanthin gradually increased.
In the transgenic approach, the β-carotene hydroxylase (BCH) gene was overexpressed in the BSH/hp3 mutant. This overexpression resulted in the gradual accumulation of zeaxanthin in the fruit during ripening, demonstrating that the overexpression of enzymes upstream in the carotenoid biosynthetic pathway can facilitate the accumulation of zeaxanthin.
These findings reveal that both breeding and transgenic approaches can be effective in enhancing zeaxanthin content in tomatoes.
Composition of Carotenoids (μg/g, FW) in "Xantomato" (a) and Control Group M82 (b): (Note: FW refers to sample fresh weight; DW refers to sample dry weight.)
Improving the cancer prevention/treatment role of carotenoids through various nano-delivery systems[4]
In recent years, research on the use of natural bioactive compounds and plant-derived chemicals for cancer prevention and treatment has been steadily increasing. Carotenoids, which include substances like lycopene, β-carotene, astaxanthin, and lutein, have garnered attention due to their anti-inflammatory, antioxidant, and free radical scavenging properties. They have also been shown to induce cell cycle arrest, apoptosis, and tumor cell differentiation, contributing to the prevention of various diseases, including cancer and cardiovascular conditions.
However, carotenoids are lipophilic compounds, and their pharmacological functions are often constrained by low solubility and limited bioavailability. The development of novel nanomaterials offers a promising opportunity for targeted delivery and controlled release of carotenoids. This article elaborates on the utilization of various types of nanomaterials to load carotenoids, enabling targeted drug delivery and controlled release. For instance, compared to free β-carotene, β-carotene carried by lipid-based nano-carriers composed of soy lecithin and cholesterol exhibits enhanced apoptosis-inducing effects, serving as a foundation for leukemia treatment. Additionally, the use of poly-L-lysine (PLL)-modified nanoliposomes to deliver lutein helps protect lutein from external conditions and facilitates its release in simulated gastric and intestinal fluids. This approach enhances cellular uptake of lutein, thereby inhibiting the development of human colon cells.
References
- García-Cerdán JG, Schmid EM, Takeuchi T, et al. Chloroplast Sec14-like 1 (CPSFL1) is essential for normal chloroplast development and affects carotenoid accumulation in Chlamydomonas. Proc Natl Acad Sci U S A. 2020 Jun 2;117(22):12452-12463.
- Hao Z, Liu S, Hu L, et a. Transcriptome analysis and metabolic profiling reveal the key role of carotenoids in the petal coloration of Liriodendron tulipifera. Hortic Res. 2020 May 1;7:70.
- Karniel U, Koch A, Zamir D, et al. Development of zeaxanthin-rich tomato fruit through genetic manipulations of carotenoid biosynthesis. Plant Biotechnol J. 2020 Nov;18(11):2292-2303.
- Zare M, Norouzi Roshan Z, Assadpour E, et al. Improving the cancer prevention/treatment role of carotenoids through various nano-delivery systems. Crit Rev Food Sci Nutr. 2021;61(3):522-534.
- Seel W, Baust D, Sons D, et al. Carotenoids are used as regulators for membrane fluidity by Staphylococcus xylosus. Sci Rep. 2020 Jan 15;10(1):330.
