Gibberellin biosynthetic pathway

Growth retardation in host plants has been associated with the use of a number of these EBI s. This effect results from the inhibition of a reaction in the gibberellin biosynthetic pathway that involves cytochrome P-450 enzymes (24). 

The carbon skeleton of the ent-kaurenoid precursors of the gibberellins is closely related to that of the diterpenoids of the ent-atiserene (10.29), ent-beyerene (10.30) and ent-trachylobane (10.31) series. The dilferences lie in the structure of ring D. The flexibility of the gibberellin biosynthetic pathway in... 

Helliwell, C.A., P.M. Chandler, A. Poole, E.S. Dennis, and W.J. Peacock (2001). The CYP88A cytochrome P450, ent-kamenoic acid oxidase, catalyzes three steps of the gibberellin biosynthetic pathway. Proc. Natl. Acad. Sci. USA 98,2065-7080. 

The gibberellin biosynthetic pathway can be divided into two major sections, the early pathway, from mevalonic acid (MVA) to GAi2 aldehyde (a single pathway), and the pathways subsequent to least four at this time). 

A simple method of screening for presumptive mutants of Gibberella fujikuroi is described. The use of one mutant (Bl-41a) in the elucidation of the gibberellin biosynthetic pathway from ent-kaurenoic acid and in the metabolism of substrate analogues is briefly reviewed. Some preliminary results are described on the investigation of the inhibition of individual biosynthetic steps by nitrogen in the medium. 

Fig. 4.58 Mechanism that rationalizes the ring contraction reaction in the conversion of eni-kaurenoic acid to a precursor of GA[2 in the gibberellin biosynthetic pathway.

Fig. 6. The gibberellin biosynthetic pathway in Zea mays shoots. The position in the pathway controlled by each of the dwarf mutants, dh d2, d2, and d5. is shown by a cross line on the appropriate arrow. This early-13-hydroxylation pathway leads to GA,. the bioactive GA controlling shoot elongation in maize. The absence of G A,. G A-,. and G A.. in the dl mutant, together with the accumulation of GA., [6]. suggest that the dl gene controls a common step leading to GA, and GA-,...

Figure 25 Biosynthetic pathways of gibberellins and diterpenoid phytoallexins in rice.

Like all steroids, brassinosteroids derive from a single common precursor mevalonic acid. Some phytohormones are synthesized totally or in part via the isoprenoid pathway, such as absdsic acid, gibberellins and cytokinins. The importance of this biosynthetic pathway in processes involved with cell cycle regulation and tumorigenesis in mammals is well documented. Having in mind the similarities between certain regulatory systems in plants and animals the question arose whether brassinosteroids as putative plant steroid hormones would show a specific effect on plant tumor cells. 

Ancymidol is classified as a plant growth regulator and has a wide application. It is taken up and translocated in the phloem and inhibits internode elongation by inhibiting the CYP enzyme in the biosynthetic pathway of gibberellins. The structures of the three above-mentioned compounds are reasonably similar ... 

Gibberellins in Higher Plants The Biosynthetic Pathway Leading to GAi... 

Spray, C. R. and B. O. Phinney, Gibberellins in higher plants The biosynthetic pathway leading to GAi in Ecology and Metabolism of Lipids (G. Fuller and W. D. Nes, eds.), ACS Symposium Series 325,25-43, American Chemical Society, Washington, DC, 1987. 

Fig. 1. Numbering system and nomenclature for the gibberellins and their precursors (Fig. from Phinney and Spray ). ent-Kaurene is the first tetracyclic hydrocarbon in the biosynthetic pathway. GA53 is a precursor to GA] the trivial names for the gibberellins are based on the order of identification, GAj to GAj. ...

Fig. 2. The MVA biosynthetic pathway leading to the cyclic diterpene, ent-kaurene. GAj 2" ldehyde is the common precursor for all known gibberellins (now numbering 72). (Figure from Phinney, ).

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