Exogenous Application of 5-Aminolevulinic Acid Promotes Coloration and Improves the Quality of Tomato Fruit by Regulating Carotenoid Metabolism

Abstract

5-Aminolevulinic acid (ALA) plays an important role in plant growth and development. It can also be used to enhance crop resistance to environmental stresses and improve the color and internal quality of fruits. However, there are limited reports regarding the effects of ALA on tomato fruit color and its regulatory mechanisms. Therefore, in this study, the effects of exogenous ALA on the quality and coloration of tomato fruits were examined. Tomato (Solanum lycopersicum “Yuanwei No. 1”) fruit surfaces were treated with different concentrations of ALA (0, 100, and 200 mg⋅L–1) on the 24th day after fruit setting (mature green fruit stage), and the content of soluble sugar, titratable acid, soluble protein, vitamin C, and total free amino acids, as well as 11 kinds of free amino acid components, intermediates of lycopene synthetic and metabolic pathways, and ALA metabolic pathway derivatives were determined during fruit ripening. The relative expression levels of genes involved in lycopene synthesis and metabolism and those involved in ALA metabolism were also analyzed. The results indicated that exogenous ALA (200 mg⋅L–1) increased the contents of soluble sugars, soluble proteins, total free amino acids, and vitamin C as well as 11 kinds of amino acid components in tomato fruits and reduced the content of titratable acids, thus improving the quality of tomato fruits harvested 4 days earlier than those of the control plants. In addition, exogenous ALA markedly improved carotenoid biosynthesis by upregulating the gene expression levels of geranylgeranyl diphosphate synthase, phytoene synthase 1, phytoene desaturase, and lycopene β-cyclase. Furthermore, exogenous ALA inhibited chlorophyll synthesis by downregulating the genes expression levels of Mg-chelatase and protochlorophyllide oxidoreductase. These findings suggest that supplementation with 200 mg⋅L–1 ALA not only enhances the nutritional quality and color of the fruit but also promotes early fruit maturation in tomato.

Exogenous DCPTA Treatment Increases Mung Bean Yield by Improving Carbon Metabolism Pathway and Up-Regulating Photosynthetic Capacity and Antioxidants

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The combined treatments of brassinolide and zeaxanthin better alleviate oxidative damage and improve hypocotyl length, biomass, and the quality of radish sprouts stored at low temperature

“…In water stress, Li and Feng (2010) found that roots soaked in brassinolide solution (0.2 mg L −1 ) could enhance soluble sugar, soluble protein, and ascorbic acid contents in Xanthoceras sorbifolia seedlings. Exogenous application of 5-aminolevulinic acid (ALA) could enhance soluble sugar, soluble protein, and ascorbic acid contents in tomato fruit by controlling carotenoids metabolism ( Wang et al, 2021 ). Liu et al (2014) found that ectopic expression of a BZR1-1D transcription factor in the brassinosteroids signaling pathway led to carotenoids accumulation and the increase of soluble sugar and vitamin C contents in tomatoes.…”

Beneficial Effects of Sodium Nitroprusside on the Aroma, Flavors, and Anthocyanin Accumulation in Blood Orange Fruits

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