Malate dehydrogenase isozymes as markers of the organelles physiological state in sugar beet ( Beta vulgaris L.)

Subcellular localization of NAD-dependent malate dehydrogenase (MDH) isozymes from sugar beet was studied with an integrative method combining differential sedimentation, isopicnic centrifugation in sucrose density and 14% starch gel electrophoresis. The ss and ll isozymes, controlled respectively by the Mdh2 and Mdh3 loci, were found to be located in the mitochondria of young leaves, and the pp isozyme, which is under control of the Mdh1 locus, was present in the microbodies. All the assayed MDH isozymes of older leaves were detected in the cytoplasm and in traced amounts in mitochondria. The use of NAD-dependent MDH isozymes for the assessment of subcellular organelles physiological state is discussed.