Cytochrome P450s in plant steroid hormone synthesis and metabolism

Abstract

Cytochrome P450s (P450s) are essential for both plant steroid hormone biosynthesis and inactivation. Synthesis of plant steroid hormones, brassinosteroids (BRs), requires P450s of the CYP85 clan. This includes members of the CYP85, CYP90 and CYP724B families of P450s. These enzymes are associated with the hydroxylation/oxidation of the C-2, C-3, C-6, C-22 and C-23 positions with their function being determined via genetic and biochemical approaches. P450s involved in BR metabolism belong to the CYP72C and CYP734A families in the CYP72 clan of P450s. The CYP734A family is associated with C-26 hydroxylation of BRs. The transcriptional regulation of these genes via feedback regulation provides a mechanism for the maintenance of optimum BR levels. Phylogenetic analysis of these P450s highlights that the biosynthesis and metabolism genes have evolved independently. Similar analysis suggests that the BaeyerVilliger reaction catalysed by the CYP85 family of P450s may have evolved independently in several dicotyledonous species.

Evolution of growth-promoting plant hormones

“…pollen) (Yokota 1997). Over 65 BRs have now been identified but elegant work using mutants late in the biosynthetic pathway suggests that only two C28 BRs are active, brassinolide and its precursor, castasterone (Nomura et al 2005;Nomura and Bishop 2006). BRs have been identified from many angiosperm and gymnosperm families and also from a pteridophyte (Equisetum avense), a bryophyte (Marchantia polymorpha) and a chlorophyte (Hydrodictyou reticulatum) (Kim et al 2002;Bajguz and Tretyn 2003).…”

“…The biosynthetic pathways for sterols from the cycloartenol precursor appear to be conserved across all land plants (Morikawa et al 2009). The steps leading to the BRs have also been clarified recently with the predominant C28 pathway leading from 24-methylenecholesterol to castasterone, and then to brassinolide in certain species and tissues (Fujita et al 2006;Nomura and Bishop 2006;Jager et al 2007). While a complex matrix of steps is possible, recent work has suggested a likely dominant pathway.…”

“…We also understand GA and BR biosynthesis in several model species, such as Arabidopsis thaliana, tomato (Lycopersicon esculentum Mill. ), pea (Pisum sativum L.) and rice (Orysa sativa L.) (Yokota 1997;Nomura and Bishop 2006;Yamaguchi 2008), and progress is being made in untangling auxin biosynthesis (Normanly 2010). While the presence of growth-promoting hormones across the many groups of plants has been documented extensively (e.g.…”

Salinity effects on expression of some important genes in sensitiveand tolerant grape genotypes

“…Cytochrome P450s (P450s or CYPs) are key enzymes involved in hydroxylation/oxidation reactions (Nomura and Bishop, 2006).…”

Phytoecdysteroid C2‐hydroxylase is microsomal in spinach, Spinacia oleracea L.

“…There is evidence that the first steps would differ from those of insects and even possibly differ between plant species (Reixach et al, 1999;Fujimoto et al, 2000;Dinan et al, 2009), but the types of enzymes may be similar. Thus, the different hydroxylations are expected to be catalyzed by CYP enzymes, as is the case for the biosynthesis of steroid plant growth hormones sharing some structural features with PEs, the brassinosteroids (Fujioka et al, 2002;Nomura and Bishop, 2006).…”