Differential expression of the maize catalase genes during kernel development: the role of steady-state mRNA levels

In maize three isozymic forms of catalase, CAT‐1, CAT‐2, and CAT‐3 are encoded by three distinct and unlinked structural genes (Catl, Cat2, and Cat3). Catalase activity profiles and zymogram analysis were used to examine the spatial and temporal expression of the three genes during kernel maturation. Three developmental stages of catalase expression were observed in the growing kernel. During stage 1 (6‐12 days after pollination), both Catl and Cat3 were expressed; during stage 2 (15‐18 days after pollination) only Cat1 expression was observed; and during stage 3 (21‐30 days after pollination), Cat1 and Cat2 were expressed. The major constituent tissues of the kernel were examined to determine their contribution to total kernel catalase expression. Each of the tissues was found to have a unique pattern of catalase gene expression. RNA blot analysis, using catalase gene‐specific nucleic acid probes, suggests that the differential expression of the three catalase genes observed in the kernel is regulated by controlling the distribution of steady‐state mRNA species for the three genes.