Flavonoid Accumulation Patterns of Transparent Testa Mutants of Arabidopsis

Abstract

Flavonoids have been implicated in the regulation of auxin movements in Arabidopsis. To understand when and where flavonoids may be acting to control auxin movement, the flavonoid accumulation pattern was examined in young seedlings and mature tissues of wild-type Arabidopsis. Using a variety of biochemical and visualization techniques, flavonoid accumulation in mature plants was localized in cauline leaves, pollen, stigmata, and floral primordia, and in the stems of young, actively growing inflorescences. In young Landsberg erecta seedlings, aglycone flavonols accumulated developmentally in three regions, the cotyledonary node, the hypocotyl-root transition zone, and the root tip. Aglycone flavonols accumulated at the hypocotyl-root transition zone in a developmental and tissue-specific manner with kaempferol in the epidermis and quercetin in the cortex. Quercetin localized subcellularly in the nuclear region, plasma membrane, and endomembrane system, whereas kaempferol localized in the nuclear region and plasma membrane. The flavonoid accumulation pattern was also examined in transparent testa mutants blocked at different steps in the flavonoid biosynthesis pathway. The transparent testa mutants were shown to have precursor accumulation patterns similar to those of end product flavonoids in wild-type Landsberg erecta, suggesting that synthesis and end product accumulation occur in the same cells.

Hormonal and Stress Induction of the Gene Encoding Common Bean Acetyl-Coenzyme A Carboxylase

“…4). Amazingly, the same root regions with GUS activity accumulate both flavonoids and auxins (Murphy and Taiz, 1999;Murphy et al, 2000;Peer et al, 2001;Ljung et al, 2005). In this context, it should be stressed that, in Arabidopsis roots, ChS and chalcone isomerase (Saslowsky and Winkel-Shirley, 2001) are located in sites where the PvACCase gene promoter is active (Fig.…”

“…It is noteworthy that PvACCase::GUS transgene expression during development has a strong correlation to the tissues where auxins are accumulated in Arabidopsis. For example, several studies have shown high auxin concentrations in Arabidopsis hydathodes, stipules, and root tips; furthermore, flavonoids colocalize with zones of auxin accumulation (Murphy et al, 2000;Peer et al, 2001;Aloni et al, 2003). To determine auxin responsiveness of the PvACCase gene promoter, 8-dold roots were treated with IAA.…”

Cloning and Characterization of Naringenin 8-Prenyltransferase, a Flavonoid-Specific Prenyltransferase of Sophora flavescens

“…It is not clear if SfN8DT-1 catalyzed the prenylation of kaempferol in planta, or if naringenin, a precursor of kaempferol, was first prenylated by SfN8DT-1 and then converted to 8DK in vivo. However, because kaempferol is the major flavonoid in Arabidopsis and the in vivo level of naringenin is very low, the occurrence of 8DK may be reasonable (Peer et al, 2001). The detection of an appreciable amount of 8DN in naringenin-fed transgenic Arabidopsis indicated that SfN8DT-1 was enzymatically functional in planta and contributed to the formation of prenylated flavonoids in a heterologous plant.…”

Ethylene Modulates Flavonoid Accumulation and Gravitropic Responses in Roots of Arabidopsis

“…DPBA fluorescence is the only technique that allows quantification of flavonoid abundance at a tissue-specific level. Furthermore, it has been shown in several reports that DPBA fluorescence accurately reports flavonoids as detected by microspectrofluorometry, HPLC, or mass spectroscopy (Mathesius et al, 2000;Peer et al, 2001).…”

“…Flavonoid accumulation was visualized in vivo by the fluorescence of flavonoid-conjugated DPBA after excitation with blue light (488 nm; Sheahan and Rechnitz, 1992;Murphy et al, 2000;Peer et al, 2001;Buer and Muday, 2004). Assays to determine the effect of ACC on DPBA fluorescence accumulation were performed by transplanting 5-d seedlings to control media or media containing 2.5 mM ACC and incubating for the required times before staining with DPBA and measuring intensities as described below.…”