ABSTRACT
Chromosomal localization of the three homoeologous genes encoding cytosolic aspartate aminotransferase in common wheat (Triticum aestivum cv. Chinese Spring, 2n = 6x = 42, AABBDD) was specified to: 3AL (0.42÷0.61), 3BL (0.38÷0.41) and 3DL (0.23÷0.81) by a comparative zymographic analysis of the enzymatic activities in deletion lines. It was also attempted to precisely explain the nature of the relationship between a number of genes encoding α and ß subunits and a distribution of staining intensity of cytosolic aspartate aminotransferase allozyme activity bands using aneuploid lines of common wheat with modified third pair of homoeologous chromosomes from genomes A, B and D, on which the genes encoding subunit α (genome A) and ß (genome B and D) are localized. The highest consistency between the experimental results and the theoretical distributions was achieved by substituting values of α = 0.57 and ß = 0.43 in a theoretical model. These results demonstrate that the individual participation of the diploid genome A in the biosynthesis of the cytosolic aspartate aminotransferase allozymes subunits is greater than the individual participation of the diploid genomes B and D.
ABSTRACT
Zymograms of the aspartate aminotransferase (AAT, EC 2.6.1.1) activity in leaf extracts from Aegilops and Triticum species revealed three AAT zones, denoted according to the decreasing electrophoretic mobility towards the anode as AAT-1, AAT-2 and AAT-3. The AAT activity zymograms of subcellular fractions isolated from T. aestivum seedlings made it possible to establish that the AAT-1 zone is located in the mitochondria, AAT-2 in the chloroplasts and AAT-3 in the cytoplasm. Most of the total AAT activity from wheat leaves arises from the chloroplasts and cytoplasm. The AAT-3 zone exhibited the lowest electrophoretic mobility, but 3 isoenzymes occurring within were the most visibly separated. The occurrence of a single band in this zone at the AAT-3a position (closest to the anode) for the aneuploid CS3ASDt AABBDD line (the absence of long arms of the 3rd pair of homologous chromosomes in the A genome) and at the AAT-3c position for Ae. umbellulata (genome UU), as well as three bands in the whole zone for T. durum (AABB) and T. aestivum (AABBDD) each, made it possible to evaluate the subunit composition of isoenzymes in the AAT-3 zone. The band at the AAT-3a position in the zymogram is formed from bb dimers, AAT-3b from ab and AAT-3c from aa. By comparing the distribution of isoenzyme bands intensities (the result of enzymatic activity) with the mathematical models, the frequencies of the occurrence of the a and b subunits within AAT-3 zone were evaluated. In AAT-3 from T. durum, a and b occurred at the ratio of 0.54:0.46, and in that from T. aestivum - 0.62:0.38, respectively.
