GENETIC BASIS OF THE MAJOR MALATE DEHYDROGENASE ISOZYMES IN MAIZE

[摘要] The mitochondrial MDH isozymes in the scutellum of the mature maize ( Zen mays L.) kernel are encoded by three independently inherited nuclear genes. Mdhl is located on chromosome 8 , close to the breakpoint (8 L .35) of a waxy-marked reciprocal translocation between chromosomes 8 and 9 . Mdh2 is located in the distal region of the long arm of chromosome 6 . Mdh3 is on the long arm of chromosome 3 , approximately 2.6 map units from sh2 . A modifier of the mitochondrial MDH isozymes ( Mmm ) maps approximately 27.5 units proximal to Adh1 in the central portion of the long arm of chromosome 1 . Independently assorting duplicate genes code for the soluble MDH isozymes. Mdh4 is located in the same region of chromosome 1 as Mmm, approximately 29 map units proximal to Adh1 . Mdh5 maps approximately 20 units distal to a2 in the short arm of chromosome 5 .——Intergenic and interallelic heterodimer formation occurs among gene products that occupy the same subcellular compartment. MDH isozymes were purified and analyzed by native-SDS two-dimensional polyacrylamide gel electrophoresis. The proposed mitochondrial MDH intergenic heterodimer bands were found to be composed of two subunits, which differ in their migrations on SDS gels; whereas, genetically defined homodimers contained only one type of subunit.——This evidence is discussed in terms Of two genetic models proposed for the maize mitochondrial MDH isozymes.

[学科分类] 医学（综合）