Analysis of variants affecting the catalase developmental program in maize scutellum.

The catalase of maize scutella is coded for by two loci, Cat1 and Cat2, which are differentially expressed in this tissue during early seedling growth. Two variant lines have been previously identified in which the developmental program for the expression of the Cat2 structural gene in the scutellum has been altered. Line R6-67 exhibits higher than normal levels of CAT-2 catalase in this tissue after four days of postgerminative growth. This phenotype is controlled by a temporal regulatory gene designated Car1. Line A16 exhibits a CAT-2 null phenotype. Further analysis of Car1 verifies the initial indication that it is trans-acting and exhibits strict tissue (scutellum) specificity. A screen of other available inbred lines uncovered eight additional catalase high-activity lines. All eight lines exhibit significantly higher than normal levels of CAT-2 protein. Two of these lines have been shown to be regulated by Car1 as in R6-67. Another line (A338) uncovered during the screen exhibits a null phenotype for CAT-2 protein and resembles A16. Catalase activity levels are low in the scutellum and no CAT-2 CRM (cross-reacting material) is present in the tissues of this line. Also, unlike most maize lines, CAT-2 cannot be induced in the leaf tissue of A338 upon exposure to light. Finally, a single line (A337), demonstrating a novel catalase developmental program, was identified.