Abstract
Amaranth plants contain large amounts of betalains, including betaxanthins and betacyanins. Amaranthin is a betacyanin, and its molecular structure and associated metabolic pathway differ from those of betanin in beet plants. The chlorophyll, carotenoid, betalain, and flavonoid contents in amaranth leaves were analyzed. The abundance of betalain, betacyanin, and betaxanthin was 2–5-fold higher in the red leaf sectors than in the green leaf sectors. Moreover, a transcriptome database was constructed for the red and green sectors of amaranth leaves harvested from 30-day-old seedlings. 22 unigenes were selected to analyze the expression profiles in the two leaf sectors. The RNA-sequencing data indicated that many unigenes are involved in betalain metabolic pathways. The potential relationships between diverse metabolic pathways and betalain metabolism were analyzed. The validation of the expression of 22 selected unigenes in a qRT-PCR assay revealed the genes that were differentially expressed in the two leaf sectors. Betalains were biosynthesized in specific tissues of the red sectors of amaranth leaves. Almost all of the genes related to betalain metabolism were identified in the transcriptome database, and the expression profiles were different between the red sectors and green sectors in the leaf. Amaranth plants consist of diverse metabolic pathways, and the betalain metabolic pathway is linked to a group of other metabolic pathways.
Highlights
Plant pigments mainly include anthocyanins, betalains, carotenoids, and chlorophylls [1]
An analysis of the betacyanin and betaxanthin contents in the green and red leaf sectors indicated these two pigments were more abundant in the red sectors than in the green sectors
On the basis of previous investigations by Teng et al [59] and Zheng et al[52], we identified the unigenes involved in betalain metabolism in the transcriptome following a comparison of Length Range 201–300 301–500 501–1000 1001–2000 >2000
Summary
Plant pigments mainly include anthocyanins, betalains, carotenoids, and chlorophylls [1]. Anthocyanins are commonly used as natural colorants [2,3,4,5]. Betalains, which are water-soluble nitrogen pigments, are more hydrophilic and have a higher tinctorial strength, they have physiological functions, including anti-oxidative [6] and anti-cancer [7]. Betalains may be useful for developing novel products relevant to the food and medical industries. Betalains are mainly existed in Caryophyllales species, with the exception of Caryophyllaceae and Molluginaceae species[8,9,10], as well as some higher fungi [11, 12].
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