Cell-type-specific gene expression and acatalasemic peroxisomes in a null Cat2 catalase mutant of maize

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Abstract
Cell separation studies in conjunction with immunocytochemical studies indicate that mesophyll cells and bundle-sheath cells, the dimorphic photosynthetic cell types in the leaves of the C4 plant Z. mays, differ in their catalase composition. In particular, catalase-2, the product of the Cat2 gene, is found primarily in the bundle-sheath cells, whereas catalase-3, the product of the Cat3 gene, is found primary in the mesophyll cells. EM observations reveal that bundle-sheath cells of A16, a mutant line lacking expression of the Cat2 gene in all tissues examined, contain numerous peroxisomes, but they are acatalasemic as determined by staining with 3,3-diaminobenzidine. The significance of this mutant in physiological studies is discussed.