Sumie Kato

Organelle DNA polymorphism in apple cultivars and rootstocks

SummaryRestriction fragment length polymorphisms (RFLPs) have been used to detect chloroplast (cp) and mitochondrial (mt) DNA variation among 18 apple cultivars and three rootstocks. The distribution of RFLP patterns allowed the assignment of these genotypes into three groups of cytoplasmic relatedness. Our results also demonstrate maternal inheritance of cp- and mtDNAs in apple. Thus, the organelle DNA assay provides a convenient and reliable method to assess cytoplasmic diversity within the apple germ-plasm collection and to trace the maternal lineages involved in the evolution of apple.

Evolutionary changes in the structures of the cox2 and atp6 loci in the mitochondrial genome of soybean involving recombination across small interspersed sequences

Abstract Mitochondrial DNA (mtDNA) fragments that contained cox2 or atp6 loci were cloned from three accessions of wild soybean (Glycine soja) in order to understand the evolutionary changes of mitochondrial genomes in the genus Glycine subgenus Soja. Cox2 was cloned as a single configuration, while atp6 was cloned as either one or two configurations from each accession. Structural variations were detected in the 5′ upstream region of cox2 and in both the 5′ upstream and 3′ downstream regions of atp6. These variations appeared to be the results of recombination events. A comparison of the mtDNA fragments previously cloned from a cultivated soybean (G. max) and a wild soybean revealed various sites of recombination, as well as various combinations of the 5′ and 3′ regions, at the cox2 and atp6 loci. Some of the cloned fragments were found to contain a set of repeated sequences, namely 299-bp and 23-bp repeats in the 5′ region of cox2 or atp6, which were interspersed in the mitochondrial genome in the subgenus Soja. Recombination events involving the 299-bp or 23-bp repeated sequences were shown to account for the generation of structural variations in the 5′ regions of these loci.

Analysis of mitochondrial DNA of an endangered beech species, Fagus hayatae Palibin ex Hayata

Mitochondrial DNA restriction fragment length polymorphisms were used to examine cytoplasmic diversity within a relic-like population of Fagus hayatae, located in northern Taiwan. Fifteen trees were surveyed for three restriction endonucleases (BamHI, EcoRI and HindIII) and five mitochondrial gene probes (atpA, atp6, atp9, coxI and coxII). The analysis failed to reveal any polymorphisms, an observation that suggests cytoplasmic uniformity in the F. hayatae population examined. It is also interesting to note that the chondriome type of our F. hayatae samples is very close to that characteristic of F. crenata populations in the southernmost area of Japan.

Mitochondrial DNA analysis reveals cytoplasmic variation within a single cultivar of perennial ryegrass (Lolium perenne L.)

SummaryThe extent of mitochondrial DNA restriction fragment length polymorphisms among individual plant samples of perennial ryegrass was determined. A total of 72 plants from three cultivars Yorktown II, S23 and Riikka were surveyed using three restriction enzymes (BamHI,EcoRI andHindIII) and three mitochondrial gene probes (coxI, coxIII andnad9). Polymorphisms were noted within each of the two cultivars Yorktown II and S23, whereas in ‘Riikka’ no variation was detected. It seems most likely that the mitochondrial genome diversity within the same cultivar has resulted from non-homogeneous ancestor cytoplasms. The hybridization-based assay employed is simple to perform, gives unambiguous results, and may thus be used in mass screening of perennial ryegrass populations for breeding purpose.