Purple: H+-ATPase; blue: AUX1; dashed arrow: diffusion

Yellow: PIN proteins; red: PGPs

PINs/PGP proteins:

Tissue-specific distribution of PIN efflux facilitator proteins

br2 mutant:

Normal tassels and ear, but compact lower stalks

Auxin transport inhibitors

efflux inhibitor

influx inhibitor

Aglycone flavonoids

displace NPA

isoflavones

Actin-dependent PIN complex cycling

Auxin transport inhibitors may act by interfering with PIN1 complex cycling

Web Essay 19.1

PLoS ONE (January 2008)

In dark: PIN2, in vacuole;

In light: predominantly in PM

Physiological effects of auxin – cell elongation

Endogenous vs. Exogenous auxin

Oat coleoptile sections

Suc maintain turgor pressure; can be substituted by KCl; 15 min lag time

The optimal auxin concentration– pea stem or oat coleoptile sections

ppm (ethylene induction)

For roots: opt. 10-10 to 10-9 M; 10-6 M inhibition

Not only for IAA level but also for auxin types for different cells

10 M IAA, 2% sucrose

The characteristics of auxin induce stem growth: acquire energy is inhibited when the presence of inhibitor of metabolic, protein synthesis

(cycloheximide), or RNA synthesis the limiting time of lag phase could not be shortened some biochemical machinery involved

0.5 h

Auxin-induced elongation vs. cell wall acidification

Maize coleoptile

lag time

Current models for IAA-induced H+ extrusion

(cell wall loosening proteins)

ABP1: track H+-ATPase to membrane

(auxin-binding protein)

Receptor (?)

p. 503 polyubiquitin