In Meristematic zone, 

cells divide both in the direction of the root base to form cells that will differentiate into the tissues of the functional root and in the direction of the root apex to form the root cap

TLS Online TPP Program

#Id: 9356

#XL - T Zoology

RI will not bind to RII unless RII is bound to TGF-β.

TLS Online TPP Program

#Id: 9357

#XL - T Zoology

RII phosphorylates serine and threonine in the juxtamembrane segment of the RI (ligand induced receptor hetero-oligomerization), releasing the inhibition of RI kinase activity.

TLS Online TPP Program

#Id: 9358

#XL - T Zoology

Active type I receptor kinase phosphorylates a Smad

TLS Online TPP Program

#Id: 9359

#XL - T Zoology

Three types of Smad proteins function in the TGF-β signaling pathway: 

R-Smads (Smad2 and Smad3)

Co-Smads (Smad4)

I-Smads (Smad7)

TLS Online TPP Program

#Id: 9360

#XL - T Zoology

Smad2/3 become phosphorylated by active RI receptors and together with Smad4 move into the nucleus to activate gene transcription

TLS Online TPP Program

#Id: 9361

#XL - T Zoology

R-Smads comprising: 

An N-terminal MH1 domain

A central proline-rich linker 

A C-terminal MH2 domain