<P> One or two genes encode the enzymes responsible for the first steps of GA biosynthesis in Arabidopsis and rice . The null alleles of the genes encoding CPS, KS, and KO result in GA - deficient Arabidopsis dwarves . Multigene families encode the 2ODDs that catalyze the formation of GA12 to bioactive GA4 . </P> <P> AtGA3ox1 and AtGA3ox2, two of the four genes that encode GA3ox in Arabidopsis, affect vegetative development . Environmental stimuli regulate AtGA3ox1 and AtGA3ox2 activity during seed germination . In Arabidopsis, GA20ox overexpression leads to an increase in GA concentration . </P> <P> Most bioactive GAs are located in actively growing organs on plants . Both GA20ox and GA3ox genes (genes coding for GA 20 - oxidase and GA 3 - oxidase) and the SLENDER1 gene (a GA signal transduction gene) are found in growing organs on rice, which suggests bioactive GA synthesis occurs at their site of action in growing organs in plants . During flower development, the tapetum of anthers is believed to be a primary site of GA biosynthesis . </P> <P> Arabidopsis, a plant, and Gibberella fujikuroi, a fungus, possess different GA pathways and enzymes . P450s in fungi perform functions analogous to the functions of KAOs in plants . The function of CPS and KS in plants is performed by a single enzyme, CPS / KS, in fungi . In fungi, the GA biosynthesis genes are found on one chromosome, but in plants, they are found randomly on multiple chromosomes . Plants produce low amount of GA3, therefore the GA3 is produced for industrial purposes by microorganisms . Industrially the gibberellic acid can be produced by submerged fermentation, but this process presents low yield with high production costs and hence higher sale value, nevertheless other alternative process to reduce costs of the GA3 production is Solid - State Fermentation (SSF) that allows the use of agro-industrial residues . </P>

Role of gibberellins in plant growth and development