(CIE A2 Biology) Gibberellin

the Le gene

a gene found in some plants for the purpose of dictating their heights whose dominant allele produces tall plants by producing a functional enzyme

active gibberellin GA₁

a plant hormone that stimulates plant cell division and stem elongation

the purpose of the enzyme produced by the Le gene

to produce active gibberellin GA₁ through a pathway (if a plant is homozygous recessive for the Le gene this enzyme’s non-functional form is produced with only a single amino acid substituted)

transcription factors

molecules that can bind to a gene’s promoter region to either promote or inhibit gene transcription

PIF

a plant transcription factor that activates amylase gene transcription with the help of gibberellin hormones

the purpose of the gibberellin hormone influencing amylase gene transcription

to control seed germination by influencing amylase gene transcription (the more gibberellin in a germinating seed the more amylase mRNA will be present there)

the first step of the gibberellin control process

gibberellin binding to gibberellin receptors to initiate DELLA breakdown by an enzyme

the second step of the gibberellin control process

PIF being released from DELLA to bind to the promoter region of the amylase gene and initiate transcription