The coding sequence of firefly luciferase reporter gene affects specific hyperexpression in Arabidopsis thaliana cpl1 mutant.

Forward genetic screening of mutants using firefly luciferase (LUC) reporter gene became a standard practice in plant research. Such screenings frequently identified alleles of CPL1 (Carboxyl-terminal Phosphatase-Like 1) regardless of promoters or pathways studied. Expression of the corresponding endogenous genes often shows the minimal difference between wild type and cpl1. Here we show that the LUC coding sequence is responsible for the high expression in cpl1, using a classical RD29a-LUC. Deletion of the LUC 30-UTR did not change hyperactivation of LUC in cpl1. However, a codon-modified LUC (LUC2) produced similar expression levels both in wild type and in cpl1. These results indicate that the coding region of LUC is responsible for the cpl1-specific LUC overexpression uncoupled with the expression of the endogenous counterpart.