Spatial and temporal responses of the maize catalases to low temperature

Abstract

Catalase (H2O2:H2O2 oxidoreductase, EC 1.11.1.6) is a primary antioxidant enzyme that can remove H2H2 rapidly and prevent the formation of reactive oxygen species. The maize (Zea mays L.) catalase genes are regulated in their expression spatially and temporally. Using embryos from germinating seeds and developing kernels from the maize standard inbred line W64A, which expresses all three Cat genes, and the CAT‐2 null line A338F, we have examined the response of the three catalase genes to low temperatures (14°C, 4°C, or 14/4°C). Total catalase activity increased in response to low temperatures in germinating embryos of both maize lines. Zymogram analysis showed that the increase in total catalase activity was due to accumulation of the CAT‐1 and CAT‐2 isozymes in the scutella and embryonic axes of germinating embryos. In both lines, CAT‐3 activity decreased in the embryonic axes of germinating embryos in response to low temperatures. The steady‐state levels of Cat transcripts did not parallel the pattern of the corresponding catalase proteins, indicating the involvement of post‐transcriptional control mechanisms. In contrast to germinating embryos and excepting an increase at 4°C in A338F, total catalase activity decreased in response to low temperatures in scutella of developing embryos of both lines. CAT‐2 activity (in W64A) and CAT‐3 activity (in A338F) decreased in response to low temperatures and their corresponding steady‐state levels of mRNA also decreased. Only CAT‐1 activity increased dramatically at 4°C in A338F, but Cat I transcript level did not change. Our data indicate that the three maize catalase genes respond differentially to low temperatures at two different developmental stages.