Auxin steers numerous physiological processes in plants, making the tight control of its endogenous levels and spatiotemporal distribution a necessity. This regulation is achieved by different mechanisms, including auxin biosynthesis, metabolic conversions, degradation, and transport. Here, we introduce cis-cinnamic acid (c-CA) as a novel and unique addition to a small group of endogenous molecules affecting in planta auxin concentrations. c-CA is the photo-isomerization product of the phenylpropanoid pathway intermediate trans-CA (t-CA). When grown on c-CA-containing medium, an evolutionary diverse set of plant species were shown to exhibit phenotypes characteristic for high auxin levels, including inhibition of primary root growth, induction of root hairs, and promotion of adventitious and lateral rooting. By molecular docking and receptor binding assays, we showed that c-CA itself is neither an auxin nor an anti-auxin, and auxin profiling data revealed that c-CA does not significantly interfere with auxin biosynthesis. Single cell-based auxin accumulation assays showed that c-CA, and not t-CA, is a potent inhibitor of auxin efflux. Auxin signaling reporters detected changes in spatiotemporal distribution of the auxin response along the root of c-CA-treated plants, and long-distance auxin transport assays showed no inhibition of rootward auxin transport. Overall, these results suggest that the phenotypes of c-CA-treated plants are the consequence of a local change in auxin accumulation, induced by the inhibition of auxin efflux. This work reveals a novel mechanism how plants may regulate auxin levels and adds a novel, naturally occurring molecule to the chemical toolbox for the studies of auxin homeostasis.

• MeSH
• Arabidopsis účinky léků   růst a vývoj   MeSH
• cinnamáty chemie   metabolismus   farmakologie   MeSH
• cyklin B genetika   metabolismus   MeSH
• geneticky modifikované rostliny MeSH
• isomerie MeSH
• kořeny rostlin účinky léků   růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• mechy účinky léků   růst a vývoj   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• proteiny Qa-SNARE genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• Selaginellaceae účinky léků   růst a vývoj   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cinnamáty MeSH
• cinnamic acid MeSH Prohlížeč
• CycB1 protein, Arabidopsis MeSH Prohlížeč
• cyklin B MeSH
• KNOLLE protein, Arabidopsis MeSH Prohlížeč
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• proteiny Qa-SNARE MeSH

Here we present an overview of what is known about endogenous plant compounds that act as inhibitors of hormonal transport processes in plants, about their identity and mechanism of action. We have also summarized commonly and less commonly used compounds of non-plant origin and synthetic drugs that show at least partial 'specificity' to transport or transporters of particular phytohormones. Our main attention is focused on the inhibitors of auxin transport. The urgent need to understand precisely the molecular mechanism of action of these inhibitors is highlighted.

• Klíčová slova
• Abscisic acid, Auxin, Cell biology, Cytokinins, Inhibitors, Plant hormones, Strigolactones, Transport,
• MeSH
• biologické modely MeSH
• biologický transport MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostlinné proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH

The phenylpropanoid 3,4-(methylenedioxy)cinnamic acid (MDCA) is a plant-derived compound first extracted from roots of Asparagus officinalis and further characterized as an allelochemical. Later on, MDCA was identified as an efficient inhibitor of 4-COUMARATE-CoA LIGASE (4CL), a key enzyme of the general phenylpropanoid pathway. By blocking 4CL, MDCA affects the biosynthesis of many important metabolites, which might explain its phytotoxicity. To decipher the molecular basis of the allelochemical activity of MDCA, we evaluated the effect of this compound on Arabidopsis thaliana seedlings. Metabolic profiling revealed that MDCA is converted in planta into piperonylic acid (PA), an inhibitor of CINNAMATE-4-HYDROXYLASE (C4H), the enzyme directly upstream of 4CL. The inhibition of C4H was also reflected in the phenolic profile of MDCA-treated plants. Treatment of in vitro grown plants resulted in an inhibition of primary root growth and a proliferation of lateral and adventitious roots. These observed growth defects were not the consequence of lignin perturbation, but rather the result of disturbing auxin homeostasis. Based on DII-VENUS quantification and direct measurement of cellular auxin transport, we concluded that MDCA disturbs auxin gradients by interfering with auxin efflux. In addition, mass spectrometry was used to show that MDCA triggers auxin biosynthesis, conjugation, and catabolism. A similar shift in auxin homeostasis was found in the c4h mutant ref3-2, indicating that MDCA triggers a cross talk between the phenylpropanoid and auxin biosynthetic pathways independent from the observed auxin efflux inhibition. Altogether, our data provide, to our knowledge, a novel molecular explanation for the phytotoxic properties of MDCA.

• MeSH
• 4-monooxygenasa kyseliny skořicové antagonisté a inhibitory   metabolismus   MeSH
• Arabidopsis účinky léků   genetika   metabolismus   MeSH
• benzoáty metabolismus   farmakologie   MeSH
• biosyntetické dráhy účinky léků   MeSH
• cinnamáty chemie   metabolismus   farmakologie   MeSH
• fenylpropionáty chemie   metabolismus   farmakologie   MeSH
• geneticky modifikované rostliny MeSH
• hmotnostní spektrometrie MeSH
• homeostáza účinky léků   MeSH
• koenzym A-ligasy antagonisté a inhibitory   metabolismus   MeSH
• konfokální mikroskopie MeSH
• kořeny rostlin účinky léků   genetika   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• lignin biosyntéza   MeSH
• semenáček účinky léků   genetika   růst a vývoj   metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 4-coumarate-CoA ligase MeSH Prohlížeč
• 4-monooxygenasa kyseliny skořicové MeSH
• benzoáty MeSH
• cinnamáty MeSH
• cinnamic acid MeSH Prohlížeč
• fenylpropionáty MeSH
• koenzym A-ligasy MeSH
• kyseliny indoloctové MeSH
• lignin MeSH
• phenylpropanoid 3,4-(methylenedioxy)cinnamic acid MeSH Prohlížeč
• piperonylic acid MeSH Prohlížeč

Flavonols are a group of secondary metabolites that affect diverse cellular processes. They are considered putative negative regulators of the transport of the phytohormone auxin, by which they influence auxin distribution and concomitantly take part in the control of plant organ development. Flavonols are accumulating in a large number of glycosidic forms. Whether these have distinct functions and diverse cellular targets is not well understood. The rol1-2 mutant of Arabidopsis thaliana is characterized by a modified flavonol glycosylation profile that is inducing changes in auxin transport and growth defects in shoot tissues. To determine whether specific flavonol glycosides are responsible for these phenotypes, a suppressor screen was performed on the rol1-2 mutant, resulting in the identification of an allelic series of UGT89C1, a gene encoding a flavonol 7-O-rhamnosyltransferase. A detailed analysis revealed that interfering with flavonol rhamnosylation increases the concentration of auxin precursors and auxin metabolites, whereas auxin transport is not affected. This finding provides an additional level of complexity to the possible ways by which flavonols influence auxin distribution and suggests that flavonol glycosides play an important role in regulating plant development.

• Klíčová slova
• Arabidopsis thaliana, UGT89C1, auxin, auxin transport, auxin turnover, flavonoid, flavonol glycosides, flavonols, metabolism, rhamnose*, rol1-2, transport,
• MeSH
• Arabidopsis genetika   růst a vývoj   metabolismus   MeSH
• flavonoly metabolismus   MeSH
• glukosyltransferasy genetika   metabolismus   MeSH
• hexosyltransferasy chemie   genetika   metabolismus   MeSH
• homeostáza MeSH
• kyseliny indoloctové metabolismus   MeSH
• molekulární sekvence - údaje MeSH
• proteiny huseníčku chemie   genetika   metabolismus   MeSH
• rhamnosa metabolismus   MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• vývoj rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• flavonoly MeSH
• glukosyltransferasy MeSH
• hexosyltransferasy MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• rhamnosa MeSH
• RHM1 protein, Arabidopsis MeSH Prohlížeč
• UGT89C1 protein, Arabidopsis MeSH Prohlížeč