High impact information on LDOX

• Anthocyanidin synthase (ANS), a member of the 2-oxoglutarate-dependent dioxygenase family in flavonoid biosynthesis, catalyzes the conversion of leucoanthocyanidins (e.g. 2R,3S,4S-cis-leucocyanidin, LCD) to flav-2-en-3,4-diols, a direct precursor of colored anthocyanidins via flavan-3,3,4-triols [1].
• In an AtMYB32 insertion mutant, the transcript levels of the DIHYDROFLAVONOL 4-REDUCTASE and ANTHOCYANIDIN SYNTHASE genes decreased while the level of the CAFFEIC ACID 0-METHYLTRANSFERASE transcript increased [2].
• Independent Arabidopsis lines with a T-DNA insertion in the LDOX gene had a similar phenotype, and one was allelic to tds4-1 [3].
• The seed phenotype of ban tds4 double mutants showed that LDOX precedes BANYULS (BAN) in the PA pathway, confirming recent biochemical characterisation of BAN as an anthocyanidin reductase [3].
• Transmission electron microscopy (TEM) showed that the pattern observed when seeds of tds4 were stained with DMACA was a result of the accumulation of PA intermediates in the cytoplasm of endothelial cells [3].

Biological context of LDOX

• DNA blot analysis was used to screen the Arabidopsis genome for sequences related to FLS and LDOX and to determine the positions of the two clones on the RI map [4].
• Moreover, the enzymatic dimerization of catechin monomers is reported for the first time suggesting a role for ANS beyond the oxidation of leucocyanidins [5].
• This and other studies led to the proposal that ANS as well as FLS may select for dihydroflavonoid substrates carrying a "beta-face" C-3 hydroxyl group and initially form the 3-geminal diol by "alpha-face" hydroxylation [5].
• The crystal structure of ANS reveals a multicomponent active site containing metal, cosubstrate, and two molecules of a substrate analog (dihydroquercetin) [6].

Anatomical context of LDOX

• Fluorescent marker dyes were used to show that tds4 endothelial cells had multiple small vacuoles, instead of a large central vacuole as observed in the wild types (WT) [3].

Associations of LDOX with chemical compounds

• These studies indicate that FLS is an "early" flavonoid gene in Arabidopsis seedlings, whereas LDOX is a "late" gene [4].
• The Arabidopsis TDS4 gene encodes leucoanthocyanidin dioxygenase (LDOX) and is essential for proanthocyanidin synthesis and vacuole development [3].
• Anthocyanidin synthase from Gerbera hybrida catalyzes the conversion of (+)-catechin to cyanidin and a novel procyanidin [5].
• Assays with recombinant ANS from Gerbera hybrida fully supported the proposal and were extended to catechin and epicatechin isomers as potential substrates to delineate the enzyme specificity [5].
• Anthocyanidin synthase (ANS), a 2-oxoglutarate iron-dependent oxygenase, catalyzes the penultimate step in the biosynthesis of the anthocyanin class of flavonoids [6].

Analytical, diagnostic and therapeutic context of LDOX

• From PCR and sequence analysis, two of the three tt18 mutant alleles were found to have a small deletion within the LDOX gene and the other was revealed to contain a rearrangement [7].
• Purification, crystallization and preliminary X-ray diffraction of anthocyanidin synthase from Arabidopsis thaliana [8].

References