Firefly luciferase (LUC) is a sensitive and versatile reporter for the analysis of gene expression. Transgenic plants carrying CLOCK GENE promoter:LUC fusions can be assayed with high temporal resolution. LUC measurement is sensitive, noninvasive, and nondestructive and can be readily automated, greatly facilitating genetic studies. For these reasons, LUC fusion analysis is a mainstay in the st...