The crystal structure of PCNA closely resembles the E. coli b subunit: A trimer forms a ring that surrounds the DNA.  The sequence and subunit organization are different from the dimeric b2 clamp; however, the function is likely to be similar.

TLS Online TPP Program

#Id: 7524

#Unit 6. System Physiology – Plant

Auxin-induced proton extrusion acidifies the cell wall and increases cell extension Auxin increase the rate of proton extrusion (wall acidification), and the kinetics of proton extrusion should closely match those of auxin-induced growth.

TLS Online TPP Program

#Id: 7525

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7526

#Unit 6. System Physiology – Plant

AUXIN SIGNAL TRANSDUCTION PATHWAYS

TLS Online TPP Program

#Id: 7527

#Unit 6. System Physiology – Plant

The auxin receptor is composed of two proteins: the SCF complex component TIR1 and the repressor protein AUX/IAA. Ubiquitin moieties are first activated by E1 ligase and added to target proteins by E2 ligase. 

TLS Online TPP Program

#Id: 7528

#Unit 6. System Physiology – Plant

TIR1 recruits AUX/ IAA proteins to the SCF -TIR1 complex in an auxin-dependent manner. Once recruited by auxin, AUX/IAA proteins are ubiquitinated by the E3 ligase activity of the SCF-TIR1 complex, which marks the protein for destruction by the 26S proteasome.

TLS Online TPP Program

#Id: 7529

#Unit 6. System Physiology – Plant

PHYSIOLOGICAL EFFECTS OF AUXIN:

Three main guidance systems control the orientation of plant growth:

Phototropism, 

Gravitropism, 

Thigmotropism