There are five phytochrome isoforms in angiosperms

TLS Online TPP Program

#Id: 620

#Unit 2. Cellular Organization

At high or low trp concentration, RNA Polymerase synthesizes full mRNA till region 4

TLS Online TPP Program

#Id: 621

#Unit 2. Cellular Organization

Attenuator riboswitch (Leader sequence) region 1 is translated  till UGA (R1-2) at high trp concentration due to two conditions

1. Ribosome quickly crosses codon 10, 11

2. After crossing codon 10, 11 ribosome prematurely terminated at UGA at the end of Region 1

TLS Online TPP Program

#Id: 622

#Unit 2. Cellular Organization

During Attenuation, Region 3-4 forms hairpin then second hairpin is formed between Region 1-2

TLS Online TPP Program

#Id: 623

#Unit 2. Cellular Organization

Dual hairpin formation take place due to ribosome fall from UGA

TLS Online TPP Program

#Id: 624

#Unit 2. Cellular Organization

Dual hairpin formation (Region 3-4 forms hairpin then second hairpin is formed between Region 1-2) release RNA-DNA hybrid and RNA Polymerase causes seizing transcription of trp operon at high trp concentration.

TLS Online TPP Program

#Id: 625

#Unit 2. Cellular Organization

Attenuator riboswitch (Leader sequence) region 1 is translated atleast till codon 10 and 11 in case of Low trp concentration because ribosomes get stalled due to low availability of charged tRNA-trp