The colorless flavonoids of Arabidopsis Thaliana (Brassicaceae). I. A model system to study the orthodihydroxy structure

Abstract

The orthodihydroxy structure may mediate flavonoid coloration or antioxidant activity, making it of interest to floral or health food industries, respectively. In the first of two companion papers, the authors demonstrate a model system to study the orthodihydroxy structure in colorless flavonoids of Arabidopsis, with tools similar to those used upon the colored flavonoids. The system includes a fluorescent staining procedure to visualize colorless orthodihydroxy flavonoids at a subcellular level and to screen seedlings for rare genetic recombinants. The system also includes mutant lines to study the synthesis of colorless orthodihydroxy flavonoids, their potential role as antioxidants, and their potential risk as oxidative mutagens.

The biosynthesis of flavonoids is enhanced similarly by UV radiation and root zone salinity in L. vulgare leaves

“…100 L of 0.5% NH 3 solution (to overcome potential problems due to pH-inhibited diffusion of NR in the vacuole of epidermal cells (Sheahan et al, 1998), using a plastic syringe without the needle, through a pinhole (made with a 100 L pipette tip) on the upper leaf end. A leaf piece of approx.…”

The colorless flavonoids of Arabidopsis thaliana (Brassicaceae). II. Flavonoid 3‘ hydroxylation and lipid peroxidation

“…The most abundant hydroxycinnamic acid (HCA) phenolics of Arabidopsis leaves are its sinapate esters (Chapple et al, 1992), and the most abundant flavonoids are its kaempferol derivatives (Li et al, 1993) as is common within the Brassicaceae (Herrmann, 1976). The sinapate esters have greater UV-B attenuation (Sheahan, 1996) and antioxidant activity (Landry, Chapple, andLast, 1995, Rao, Paliyath, andOrmrod, 1996) than flavonoids in Arabidopsis. Efforts to enhance the UV-B attenuation or antioxidant activity of phenolics will require an understanding of both phenomena.…”

“…Phenolic symmetry enhances the efficiency of UV-B absorption. Although studies of plant phenolic UV-B attenuation rarely distinguish between hydroxycinamates (HCAs) and flavonoids (Sheahan, 1996) screens (Shaath, 1990). Major commercial sunscreens contain phenolic structures equivalent to the HCAs of plants, and one might expect the sinapate esters of Arabidopsis to be efficient UV-B protectants.…”

Flavonoids Are Differentially Taken Up and Transported Long Distances in Arabidopsis

“…Fluorescence microscopy of seedlings stained with diphenylboric acid 2-aminoethyl ester (DPBA; fluoresces upon binding flavonoids) provides a powerful tool to examine the accumulation, localization, and movement of flavonoids in living plants (Sheahan et al, 1998;Murphy et al, 2000;Peer et al, 2001;Wasson et al, 2006). Arabidopsis transparent testa4 (tt4) mutants treated with DPBA have only dim green fluorescence ), as they lack flavonoids (Sheahan and Rechnitz, 1993;Burbulis et al, 1996;Sheahan et al, 1998).…”

“…Arabidopsis transparent testa4 (tt4) mutants treated with DPBA have only dim green fluorescence ), as they lack flavonoids (Sheahan and Rechnitz, 1993;Burbulis et al, 1996;Sheahan et al, 1998). DPBA generates compoundspecific fluorescence Wuyts et al, 2006).…”