Kaempferol 3‐O‐rhamnoside‐7‐O‐rhamnoside is an endogenous flavonol inhibitor of polar auxin transport in Arabidopsis shoots

Abstract

Polar auxin transport (PAT) plays key roles in the regulation of plant growth and development. Flavonoids have been implicated in the inhibition of PAT. However, the active flavonoid derivative(s) involved in this process in vivo has not yet been identified. Here, we provide evidence that a specific flavonol bis-glycoside is correlated with shorter plant stature and reduced PAT.Specific flavonoid-biosynthetic or flavonoid-glycosylating steps were genetically blocked in Arabidopsis thaliana. The differential flavonol patterns established were analyzed by high-performance liquid chromatography (HPLC) and related to altered plant stature. PAT was monitored in stem segments using a radioactive [3H]-indole-3-acetic acid tracer.The flavonoid 3-O-glucosyltransferase mutant ugt78d2 exhibited a dwarf stature in addition to its altered flavonol glycoside pattern. This was accompanied by reduced PAT in ugt78d2 shoots. The ugt78d2-dependent growth defects were flavonoid dependent, as they were rescued by genetic blocking of flavonoid biosynthesis. Phenotypic and metabolic analyses of a series of mutants defective at various steps of flavonoid formation narrowed down the potentially active moiety to kaempferol 3-O-rhamnoside-7-O-rhamnoside. Moreover, the level of this compound was negatively correlated with basipetal auxin transport.These results indicate that kaempferol 3-O-rhamnoside-7-O-rhamnoside acts as an endogenous PAT inhibitor in Arabidopsis shoots.

Hormone-regulated defense and stress response networks contribute to heterosis inArabidopsisF1 hybrids

“…Flavonoids are repressors of auxin transport (27,28), and all three hybrids showed a down-regulation of genes involved in flavonoid biosynthesis ( Fig. 2 C and D), implying a reduction in flavonoid levels in the hybrids and presumably increased rates of IAA transport compared with the parental lines; the latter is confirmed for C24/Ler (26).…”

“…In the Arabidopsis hybrids, the increased auxin response mainly involves changes at the level of auxin biosynthesis involving repression of genes involved in producing the defense compounds, indole glucosinolates, and camalexin. Changes in flavonoid biosynthesis also contribute because flavonoids are negative regulators of polar auxin transport (27,28). Even moderate decreases in flavonoid biosynthesis gene expression improve plant growth (27).…”

cis-Cinnamic Acid Is a Novel, Natural Auxin Efflux Inhibitor That Promotes Lateral Root Formation

“…Flavonols and flavonoids such as quercetin were considered to inhibit auxin transporters (Brown et al, 2001), although later work suggested that flavonoids also act by redirecting PIN efflux protein localization (Santelia et al, 2008). Certain flavonoid mutants display auxin-related defects (Buer et al, 2013) and an auxin-transport inhibiting activity was recently assigned to the flavonol glycoside kaempferol 3-O-rhamnoside-7-O-rhamnoside (Yin et al, 2014).…”

Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1

“…For example, an Arabidopsis flavonoid 3-O-glycosyltransferase mutant, which overaccumulated kaempferol 3-O-rhamnoside-7-O-rhamnoside, showed reduced polar auxin transport (Yin et al, 2014). Similarly, auxin transport phenotypes in several Arabidopsis flavonoid mutants have been linked to altered accumulation of flavonoid glycosides as they contain undetectable levels of free kaempferol or quercetin aglycones (Buer et al, 2013).…”