Investigating the Role of the Circadian Clock Genes PRR5, PRR7, and PRR9 in Regulating Plant Immunity

Abstract

Successful defense against pathogens is critical for plant survival. Recent studies have shown that the circadian clock, the internal time measuring machinery, is involved in disease resistance in addition to its roles in plant development. One such protein, LUX, binds to the promoters of the clock genes PRR5, 7, and 9; and we have preliminary results to show that these genes are involved in defense. To confirm if these genes affect SA-mediated defense, we introduced individual single mutants of the genes PRR5, 7, and 9 into acd6-1, a small mutant plant with constitutive defense whose size change predicts the defense levels. We have isolated the double mutants (acd6-1prr5, acd6-1prr7, acd6-1prr9), two triple mutants (acd6-1prr5prr9 and acd6-1prr7prr9), and the quadruple mutant (acd6-1prr5prr7prr9). We are currently assessing the plant phenotypes by measuring their sizes, cell death levels, SA levels, and the expression of defense genes. Analysis of acd6-1 phenotype suppression, if any exists, will show whether the PRR5, 7, and 9 genes act in a synergistic manner in the SA pathway. Significant phenotypic recovery would be evidence for roles of these genes in defense control.