cry2 protein is preferentially degraded under blue light, whereas cry1 is much more stable.

TLS Online TPP Program

#Id: 9800

#Unit 6. System Physiology – Plant

Proportion of phytochrome in the Pfr form after saturating irradiation by red light is only about 85%. 

TLS Online TPP Program

#Id: 9801

#Unit 6. System Physiology – Plant

Very small amount of far-red light absorbed by Pr makes it impossible to convert Pfr entirely to Pr by broad spectrum far-red light. An equilibrium of 97% Pr and 3% Pfr is achieved. This equilibrium is termed the photostationary state.

TLS Online TPP Program

#Id: 9802

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 9803

#Unit 6. System Physiology – Plant

The N-terminal a PAS domain 

a GAF domain with bilin-lyase activity, which binds the chromophore, 

PHY domain, which stabilizes phytochrome in the Pfr form

TLS Online TPP Program

#Id: 9804

#Unit 6. System Physiology – Plant

PAS-related domain (PRD) repeats mediate phytochrome dimerization. 

The PRD domain targets the Pfr form of phyB to the nucleus, although it lacks a canonical nuclear localization signal (NLS).

TLS Online TPP Program

#Id: 9805

#Unit 6. System Physiology – Plant

In higher plants the phytochrome chromophore is a linear tetrapyrrole called phytochromobilin