Quantification of plant resistance to isoprenoid biosynthesis inhibitors.

Plants use two pathways for the production of the same universal isoprenoid precursors: the mevalonic acid (MVA) pathway and the methylerythritol 4-phosphate (MEP) pathway. Inhibitors of the MVA pathway prevent the activity of the shoot apical meristem and the development of true leaves in seedlings, whereas those inhibiting the MEP pathway show an additional bleaching phenotype. Here, we describe two methods to quantify plant resistance to inhibitors of the MVA pathway or the MEP pathway based on seedling establishment and photosynthetic pigment measurements. Although the methods are presented for Arabidopsis, they are valid for other plant species. These methods can be used as inexpensive and high-throughput alternatives to in vitro assays to estimate the activity of the corresponding target enzymes and to screen for mutants with altered levels or activities of these enzymes.