The UNT College of Arts and Sciences educates students in traditional liberal arts, performing arts, sciences, professional, and technical academic programs. In addition to its departments, the college includes academic centers, institutes, programs, and offices providing diverse courses of study.
Article on early steps in proanthocyanidin biosynthesis in the model legume Medicago truncatula.
Physical Description
16 p. : col. ill.
Notes
Abstract: Oligomeric proanthocyanidins (PAs) composed primarily of epicatechin units accumulate in the seed coats of the model legume Medicago truncatula, reaching maximal levels at around 20 d after pollination. Genes encoding the single Medicago anthocyanidin synthase (ANS; EC 1.14.11.19) and leucoanthocyanidin reductase (LAR; EC 1.17.1.3) were cloned and the corresponding enzymes functionally identified. Recombinant MtANS converted leucocyanidin to cyanidin, and, more efficiently, dihydroquercetin to the flavonol quercetin. Levels of transcripts encoding dihydroflavonol reductase, ANS, and anthocyanidin reductase (ANR), the enzyme responsible for conversion of anthocyanidin to (−)-epicatechin, paralleled the accumulation of PAs in developing seeds, whereas LAR transcripts appeared to be more transiently expressed. LAR, ANS, and ANR proteins were localized to the cytosol in transfected tobacco (Nicotiana tabacum) leaves. Antisense down-regulation of ANS in M. truncatula resulted in reduced anthocyanin and PA levels, but had no impact on flavonol levels. Transgenic tobacco plants constitutively overexpressing MtLAR showed reduced anthocyanin content, but no catechin or increased levels of PAs were detected either in leaves or in flowers. Our results confirm previously ascribed in vivo functions for ANS and ANR. However, the apparent lack of catechin in M. truncatula PAs, the poor correlation between LAR expression and PA accumulation, and the lack of production of catechin monomers or oligomers in transgenic plants overexpressing MtLAR question the role of MtLAR in PA biosynthesis in Medicago.
This article is part of the following collection of related materials.
UNT Scholarly Works
Materials from the UNT community's research, creative, and scholarly activities and UNT's Open Access Repository. Access to some items in this collection may be restricted.
Pang, Yongzhen; Peel, Gregory J.; Wright, Elane; Wang, Z.-Y. (Zeng-Yu), 1963- & Dixon, R. A.Early Steps in Proanthocyanidin Biosynthesis in the Model Legume Medicago truncatula,
article,
September 20, 2007;
[Rockville, Maryland].
(https://digital.library.unt.edu/ark:/67531/metadc488156/:
accessed September 17, 2024),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
crediting UNT College of Arts and Sciences.