ABSTRACT
The origin and genomic constitution of the tetraploid perennial species Dasypyrum hordeaceum (2n = 4x = 28) and its phylogenetic relationships with the annual diploid Dasypyrum villosum (2n = 2x = 14) have been investigated by comparing the two genomes using different methods. There is no apparent homology between the conventional or Giemsa C-banded karyotypes of the two Dasypyrum species, nor can the karyotype of D. hordeaceum be split up into two similar sets. Polymorphism within several chromosome pairs was observed in both karyotypes. Cytophotometric determinations of the Feulgen-DNA absorptions showed that the genome size of D. hordeaceum was twice as large as that of D. villosum. Both the cross D. villosum x D. hordeaceum (crossability rate 12.1%) and the reciprocal cross (crossability rate 50.7%) produced plump seeds. Only those from the former cross germinated, producing sterile plants with a phenotype that was intermediate between those of the parents. In these hybrids (2n = 21), an average of 13.77 chromosomes per cell paired at meiotic metaphase I. Trivalents were only rarely observed. Through dot-blot hybridizations, a highly repeated DNA sequence of D. villosum was found not to be represented in the genome of D. hordeaceum. By contrast, very similar restriction patterns were observed when a low-repeated DNA sequence or different single-copy sequences of D. villosum or two sequences in the plastidial DNA of rice were hybridized to Southern blots of the genomic DNAs of the two Dasypyrum species digested with different restriction endonucleases. By analyzing glutamic-oxaloacetic-transaminase, superoxide dismutase, alcohol dehydrogenase, and esterase isozyme systems, it was shown that both Dasypyrum species shared the same phenotypes, which differed from those found in hexaploid wheat. In situ hybridizations using DNA sequences encoding gliadins showed that these genes were located close to the centromere of three pairs of D. villosum chromosomes and that they had the same locations in six pairs of D. hordeaceum chromosomes. We conclude that the autoploid origin of D. hordeaceum from D. villosum, which cannot be defended on the basis of chromosomal traits, is suggested by the other findings obtained by comparing the two genomes. Key words : Dasypyrum hordeaceum, Dasypyrum villosum, phylogenetic relationships.
ABSTRACT
Subrepeating sequences of 325 bp found in the ribosomal intergenic spacer (IGS) of Vicia faba and responsible for variations in the length of the polycistronic units for rRNA were isolated and used as probes for in situ hybridization. Hybridization occurs at many regions of the metaphase chromosomes besides those bearing rRNA genes, namely chromosome ends and all the heterochromatic regions revealed by enhanced fluorescence after quinacrine staining. The DNA homologous to the 325 bp repeats that does not reside in the IGS was isolated, cloned and sequenced. It is composed of tandemly arranged 336 bp elements, each comprising two highly related 168 bp sequences. This structure is very similar to that of the IGS repeats and ca. 75% nucleotide sequence identity can be observed between these and the 168 bp doublets. The most obvious difference lies in the deletion, in the former, of a 14 bp segment from one of the two related sequences. It is hypothesized that the IGS repeats are derived from the 336 bp elements and have been transposed to ribosomal cistrons from other genome fractions. The possible relations between these sequences and others with similar structural features found in other species are discussed.
Subject(s)
DNA, Ribosomal/genetics , Fabaceae/genetics , Plants, Medicinal , Repetitive Sequences, Nucleic Acid , Base Sequence , Blotting, Southern , Chromosome Mapping , Cloning, Molecular , Molecular Sequence Data , RNA Probes , RNA, Ribosomal/genetics , Restriction MappingABSTRACT
Experiments were carried out on Vicia faba major involving (1) determination of the pattern of legumin accumulation during seed development, (2) protein purification from mature cotyledons, (3) the characterization of legumin mRNA, and (4) the chromosomal localization of the genes coding for legumins. In developing cotyledons the synthesis of legumin begins 28 days after petal desiccation (DAPD), and 4 days after initiation of vicilin synthesis. The two subunits (αA and ßA) of legumin A appear 2 days earlier than those (αB and ßB) of legumin B. While the accumulation of vicilin peaks on the 30th DAPD, that of legumin continues during further seed development, and the synthesis of legumin mRNA peaks on the 37th DAPD. Northern blot hybridizations using two DNA plasmids containing cDNA inserts with sequence homology to the A- and B-type legumin genes, respectively, indicated that legumin mRNAs extracted from cotyledons 36 DAPD band below the 18S RNA band. In addition, a faint band below that of the 25S RNA band can be observed in legumin mRNAs extracted from cotyledons at an earlier developmental stage (30 DAPD). By means of polyacrylamide gel electrophoresis in the presence or absence of SDS and 2-mercaptoethanol, two fractions could be eluted after zonal isoelectric precipitation of the globulins from mature seeds: one fraction contains mainly vicilin, the other, legumin. In situ hybridization showed that legumin genes are arranged in two clusters: the genes coding for legumin A are located in the longer arm of the one between the two shortest subtelocentric chromosome pairs whose centromere is in a less terminal position; those coding for legumin B are located in the non-satellited arm of the longer submetacentric pair.
ABSTRACT
This study was conducted to assess the genetic basis of the variability observed for the glutamate oxaloacetate transaminase (GOT), Superoxide dismutase (SOD), esterase (EST), and malate dehydrogenase (MDH) isozyme systems in different open-pollinated Vicia faba varieties. Individual plants showing contrasting zymogram patterns were simultaneously selfed and cross-combined. Crossing was unsuccessful in producing progeny, and only selfed progenies were suitable for genetical analysis of isozyme variability. Three zones of GOT activity were made visible. The isozyme of GOT-2 and GOT-3 zones were dimeric and under the control of three alleles at the Got-2 locus and two alleles at the Got-3 locus, respectively. The isozymes of the GOT-1 zone did not show any variability. Three zones of SOD isozyme activity were made visible. The isozymes occurring in the SOD-1 (chloroplastic isozyme form) and SOD-2 (cytosol isozyme form) zones were dimeric and under the control of two alleles at the Sod-1 and Sod-2 loci. The isozyme visualized in the SOD-3 zone (mitochondrial isozyme form) were tetrameric and under the control of two alleles at the Sod-3 locus. Apparently the isozymes made visible in the most anodal esterase zones EST-1, EST-2, and EST-3 were monomeric, and the occurrence of two alleles at each of two different loci explained the variability observed in the EST-2 and EST-3 zones. For MDH, only two five-banded zymogram pattern types were found, and every selfed progeny showed only one of the two zymogram type, indicating that each individual possessed fixed alleles at the loci controlling MDH isozyme. Got-2, Got-3, Sod-1, Sod-2, and Sod-3 appear to be five new isozyme gene markers that can be useful in Vicia faba breeding for linkage study, varietal fingerprinting, outcrossing rate estimate, and indirect selection for quantitative characters.
ABSTRACT
The biochemical complexity and its consequence has been investigated in the amphiploids M x v and CS x v derived from crossing the tetraploid wheat Triticum turgidum var durum cv 'Modoc' and the hexaploid wheat T. aestivum cv 'Chinese Spring', respectively, with Dasypyrum villosum. Electrophoretic analysis of variation in six enzyme systems (GOT, ADH, GPI, SOD, EST, and LPX) and in high molecular weight glutenin seed storage proteins indicated that in the amphiploids these proteins were specified by a minimum of seven sets of homologous genes on wheat and D. villosum chromosomes and that in each set there were allelic differences. The enzymes detected in each amphiploid were fully accounted for by simple additivity of protomers specified by the homologous genes inherited from their parents. The amphiploids also expressed novel oligomeric enzymes not produced in either one of their parents. The ascertained expression for all the alleles inherited by both parents and the resulting biochemical complexity suggested that some peculiar feature of the amphiploids such as high nitrogen content in the plant and in the kernels and their immunity to the powdery mildew disease caused by both Erysiphe graminis f.sp. tritici and E. graminis f. sp. haynaldiae may be the consequence of the indicated complexity but specified by other sets of genes. The biochemical complexity of the M x v amphiploid may be the basis for its versatility as new crop species.
ABSTRACT
The zymogram phenotypes of glucose-phosphate isomerase (GPI), alcohol dehydrogenase-1 (ADH-1), glutamate oxaloacetate transaminase (GOT), superoxide dismutase (SOD), lipoxygenase (LPX), esterase (EST) and the banding patterns of gliadin and glutenin seed storage proteins were determined for Triticum aestivum cv. 'Chinese Spring' (CS), Dasypyrum villosum, the octoploid amphiploid T. aestivum cv. 'Chinese Spring' D. villosum (CS × v) (2n=8x=56; AABBDDVV), and for five CS-D. villosum disomic addition lines. The genes Gpi-V1, Adh-V1, Got-V2, and Sod-V2 coding for GPI-1, ADH-1, GOT-2, and SOD-2 isozymes were located in D. villosum on chromosome 1V, 4V, 6V, and 7V, respectively. Genes coding for gliadin- and glutenin-like subunits are located in D. villosum chromosomes 1V. There are no direct evidence for chromosomal location of genes coding for GOT-3, EST-1 and LPX-2 isozymes. The linkage between genes coding for glutenin-like proteins and GPI-1 isozymes in chromosome 1V is evidence of homoeology between chromosome 1V and the chromosomes of homoeologous group 1 in wheat.
