S phase cyclin-CDK accumulates in late G1 , they are immediately inactivated by binding of a CKI called Sic1

TLS Online TPP Program

#Id: 9840

#Unit 6. System Physiology – Plant

Plant phytochrome is an autophosphorylating

serine/threonine kinase that may phosphorylate

other proteins

TLS Online TPP Program

#Id: 9841

#Unit 6. System Physiology – Plant

Three distinct classes of photoreceptors mediate the effects of UV-A/blue light (320–500 nm): the cryptochromes, phototropins and the ZEITLUPE (ZTL) family of proteins

TLS Online TPP Program

#Id: 9842

#Unit 6. System Physiology – Plant

Cryptochromes under blue light causes

1.Suppression of hypocotyl elongation

2.Promotion of cotyledon expansion

3.Membrane depolarization

4.Inhibition of petiole elongation

5.Anthocyanin production

6.Circadian clock entrainment

TLS Online TPP Program

#Id: 9843

#Unit 6. System Physiology – Plant

The HY4 gene encodes a 75-kDa cry1 protein with significant sequence homology to microbial DNA photolyase

TLS Online TPP Program

#Id: 9844

#Unit 6. System Physiology – Plant

Cryptochromes bind a (FAD) and the pterin 5,10 methyltetrahydrofolate (MTHF) as chromophores

TLS Online TPP Program

#Id: 9845

#Unit 6. System Physiology – Plant

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