Flavonoid accumulation patterns of transparent testa mutants of Arabidopsis

Flavonoids have been implicated in the regulation of auxin movements in Ara bidopsis. To understand when and where flavonoids may be acting to control auxin movement, the flavonoid accumulation pattern was examined in young se edlings and mature tissues of wild-type Arabidopsis. Using a variety of bio chemical and visualization techniques, flavonoid accumulation in mature pla nts was localized in cauline leaves, pollen, stigmata, and floral primordia , and in the stems of young, actively growing inflorescences. In young Land sberg erecta seedlings, aglycone flavonols accumulated developmentally in t hree regions, the cotyledonary node, the hypocotyl-root transition zone, an d the root tip. Aglycone flavonols accumulated at the hypocotyl-root transi tion zone in a developmental and tissue-specific manner with kaempferol in the epidermis and quercetin in the cortex. Quercetin localized subcellularl y in the nuclear region, plasma membrane, and endomembrane system, whereas kaempferol localized in the nuclear region and plasma membrane. The flavono id accumulation pattern was also examined in transparent testa mutants bloc ked at different steps in the flavenoid biosynthesis pathway. The transpare nt testa mutants were shown to have precursor accumulation patterns similar to those of end product flavonoids in wild-type Landsberg erecta, suggesti ng that synthesis and end product accumulation occur in the same cells.