R2R3-MYB transcription factor PpMYB17 positively regulates flavonoid biosynthesis in pear fruit
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ORIGINAL ARTICLE
R2R3‑MYB transcription factor PpMYB17 positively regulates flavonoid biosynthesis in pear fruit Apekshika T. Premathilake1,2,3,4 · Junbei Ni1,2,3 · Songling Bai1,2,3 · Ruiyan Tao1,2,3 · Mudassar Ahmad1,2,3 · Yuanwen Teng1,2,3 Received: 23 April 2020 / Accepted: 15 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Main conclusion PpMYB17 positively regulates flavonoid biosynthesis in pear fruit by activating PpCHS, PpCHI, PpF3H, and PpFLS in the flavonoid biosynthesis pathway independently of bHLH or WD40 cofactors in the MBW complex. Abstract Flavonoids are important secondary metabolites in plants. The flavonoid biosynthesis pathway is regulated by various transcription factors, with MYB transcription factors considered to be the key regulators. However, the regulation of flavonoid biosynthesis in the pear fruit has not been fully characterized. The R2R3-MYB transcription factor PpMYB17 was isolated from ‘Red Zaosu’ pear fruit and functionally characterized. An exposure to light upregulated PpMYB17 expression in the pear fruit. A phylogenetic analysis indicated PpMYB17 is related to the flavonol regulators. A subcellular localization assay suggested that PpMYB17 is a nuclear protein. Overexpression of PpMYB17 increased the flavonoid content of pear calli and Arabidopsis via the upregulated expression of structural genes in the flavonoid biosynthesis pathway, especially FLS. The LC–MS/MS analysis revealed most of the differentially accumulated flavonols, flavanones, flavones, isoflavones, and anthocyanins were significantly more abundant in PpMYB17-overexpressing calli than in wild-type calli. Moreover, PpMYB17 did not interact with PpbHLH3, PpbHLH33, or PpWD40 in a yeast system. Dual-luciferase assays demonstrated that PpMYB17 strongly activates the promoters of PpCHS, PpCHI, PpF3H, PpFLS, and PpUFGT which are key downstream genes in the flavonoid biosynthesis pathway, independently of the PpbHLH3 cofactor. These gene expression changes may enhance flavonoid biosynthesis in pear fruit. The data presented may be useful for further elucidating the flavonoid biosynthesis regulatory network, potentially leading to the development of new pear cultivars that produce fruits with increased flavonoid contents. Keywords Flavonoids · LC–MS/MS · Light · Pear · PpMYB17 · Transcription factor Abbreviations CHS Chalcone synthase CHI Chalcone isomerase
Communicated by Dorothea Bartels. Apekshika T. Premathilake and Junbei Ni contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00425-020-03473-4) contains supplementary material, which is available to authorized users. * Yuanwen Teng [email protected] Extended author information available on the last page of the article
F3H Flavanone 3-hydroxylase ANS Anthocyanin synthase FLS Flavonol synthase UFGT UDP-glucose: flavonoid 3-glucosyltransferase
Introduction Flavonoids are a group of polyphenolic compounds that are abundant in plants. The g
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