Attenuator riboswitch (Leader sequence) is made up of almost 140 nt which further can be divided into four Intra -complementary regions 

TLS Online TPP Program

#Id: 9805

#Unit 6. System Physiology – Plant

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

TLS Online TPP Program

#Id: 9806

#Unit 6. System Physiology – Plant

Pr chromophore undergoes a cis–trans isomerization between carbons 15 and 16 and rotation of the C14-C15 single bond on red light exposure.

TLS Online TPP Program

#Id: 9807

#Unit 6. System Physiology – Plant

Phytochromobilin is synthesized in plastids from chlorophyll biosynthetic pathway and transported into cytosol by a passive process.

TLS Online TPP Program

#Id: 9808

#Unit 6. System Physiology – Plant

Phytochromobilin is exported from the plastid to the cytosol where it autocatalytically attaches to the PHY apoprotein through a thioether linkage to a cysteine residue.

TLS Online TPP Program

#Id: 9809

#Unit 6. System Physiology – Plant

hy1 and hy2 mutant are chromophore biosynthesis mutant: which fail to supress hypocotyl elongation

TLS Online TPP Program

#Id: 9810

#Unit 6. System Physiology – Plant

Pfr is the physiologically active forms of Phytochrome

Wild type: short hypocotyl by white light

hy mutant (phytochrome mutant): long hypocotyl by white light