AUTHOR=Wang Junwen , Yuan Hong , Wu Yue , Yu Jihua , Ali Basharat , Zhang Jing , Tang Zhongqi , Xie Jianming , Lyu Jian , Liao Weibiao 

TITLE=Application of 5-aminolevulinic acid promotes ripening and accumulation of primary and secondary metabolites in postharvest tomato fruit

JOURNAL=Frontiers in Nutrition

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.1036843

DOI=10.3389/fnut.2022.1036843

ISSN=2296-861X

ABSTRACT=<p>5-Aminolevulinic acid (ALA) plays a vital role in promoting plant growth, enhancing stress resistance, and improving fruit yield and quality. In the present study, tomato fruits were harvested at mature green stage and sprayed with 200 mg L<sup>–1</sup> ALA on fruit surface. During ripening, the estimation of primary and secondary metabolites, carotenoids, and chlorophyll contents, and the expression levels of key genes involved in their metabolism were carried out. The results showed that ALA significantly promoted carotenoids accumulation by upregulating the gene expression levels of <italic>geranylgeranyl diphosphate synthase</italic> (<italic>GGPPS</italic>, encoding geranylgeranyl diphosphate synthase), <italic>phytoene synthase 1</italic> (<italic>PSY1</italic>, encoding phytoene synthase), <italic>phytoene desaturase</italic> (<italic>PDS</italic>, encoding phytoene desaturase), and <italic>lycopene</italic>β<italic>-cyclase</italic> (<italic>LCYB</italic>, encoding lycopene β-cyclase), whereas chlorophyll content decreased by downregulating the expression levels of <italic>Mg-chelatase</italic> (<italic>CHLH</italic>, encoding Mg-chelatase) and <italic>protochlorophyllide oxidoreductase</italic> (<italic>POR</italic>, encoding protochlorophyllide oxidoreductase). Besides, the contents of soluble solids, vitamin C, soluble protein, free amino acids, total soluble sugar, organic acid, total phenol, and flavonoid were increased in ALA-treated tomato fruit, but the fruit firmness was decreased. These results indicated that the exogenous ALA could not only promote postharvest tomato fruit ripening but also improve the internal nutritional and flavor quality of tomato fruit.</p>