Abstract: The present inventors have discovered that ferredoxin NADP oxidoreductase (FNR) is essential for plant growth. Specifically, the inhibition of FNR gene expression in plant seedlings resulted in seedlings that looked pale and very stunted. Thus, FNR can be used as a target for the identification of herbicides. Accordingly, the present invention provides methods for the identification of compounds that inhibit FNR expression or activity, comprising: contacting a compound with a FNR and detecting the presence and/or absence of binding between the compound and the FNR, or detecting a decrease in FNR expression or activity. The methods of the invention are useful for the identification of herbicides.

Abstract: The present inventors have discovered that NADPH:protochlorophyllide oxidoreductase (POR) is essential for plant growth. Specifically, the inhibition of POR gene expression in plant seedlings results in reduced growth and chlorosis. Thus, POR is useful as a target for the identification of herbicides. Accordingly, the present invention provides methods for the identification of herbicides by measuring the activity of a POR in the presence and absence of a compound, wherein an alteration of POR activity in the presence of the compound indicates the compound as a candidate for a herbicide.

Abstract: The cloning of a truncated Arabidopsis gene expressing squalene synthase, as well as the expression and purification of the squalene synthase, are described. Also described herein is a fluorescent assay using squalene synthase that is amenable to high-throughout use, particularly for studying the regulation of isoprenoid synthesis and identifying squalene synthase inhibitors and promoters. As the formation of squalene is stoichiometric with the depletion of NADPH, the activity of squalene synthase can be evaluated by following the NADPH concentration over time. Squalene synthase activity is determined by combining FPP, NADPH, squalene synthase and a magnesium ion cofactor to form a reaction mixture under conditions suitable for squalene formation, optionally in the presence of a compound being analyzed for its ability to inhibit or promote squalene synthase. The concentration of NADPH over time is determined by subjecting the reaction mixture to UV light and detecting fluorescent light emission.

Abstract: Novel DNA and enzymes such as Plant Thioredoxin-Porphobilinogen Synthase (T-PPS) or Plant Porphobilinogen Synthase (PPS), together with novel compositions thereof and methods using such enyzmes are claimed.