Chromosome assignment of four photosynthesis-related genes and their variability in wheat species

Abstract

Copy numbers of four photosynthesis-related genes, PhyA, Ppc, RbcS and Lhcb1 (*)1, in wheat genomes were estimated by slot-blot analysis, and these genes were assigned to the chromosome arms of common wheat by Southern hybridization of DNA from an aneuploid series of the cultivar Chinese Spring. The copy number of PhyA was estimated to be one locus per haploid genome, and this gene was assigned to chromosomes 4AL, 4BS and 4DS. The Ppc gene showed a low copy number of small multigenes, and was located on the short arm of homoeologous group 3 chromosomes and the long arm of chromosomes of homoeologous group 7. RbcS consisted of a multigene family, with approximately 100 copies in the common wheat genome, and was located on the short arm of group 2 chromosomes and the long arm of group 5 chromosomes. Lhcb1 (*)1 also consisted of a multigene family with about 50 copies in common wheat. Only a limited number of restriction fragments (approximately 15%) were used to determine the locations of members of this family on the long arm of group 1 chromosomes owing to the multiplicity of DNA bands. The variability of hybridized bands with the four genes was less in polyploids, but was more in the case of multigene families. RFLP analysis of polyploid wheats and their presumed ancestors was carried out with probes of the oat PhyA gene, the maize Ppc gene, the wheat RbcS gene and the wheat Lhcb1 (*)1 gene. The RFLP patterns of common wheat most closely resembled those of T. Dicoccum (Emmer wheat), T. urartu (A genome), Ae. speltoides (S genome) and Ae. squarrosa (D genome). Diversification of genes in the wheat complex appear to have occurred mainly at the diploid level. Based on RFLP patterns, B and S genomes were clustered into two major groups. The fragment numbers per genome were reduced in proportion to the increase of ploidy level for all four genes, suggesting that some mechanism(s) might operate to restrict, and so keep to a minimum, the gene numbers in the polyploid genomes. However, the RbcS genes, located on 2BS, were more conserved (double dosage), indicating that the above mechanism(s) does not operate equally on individual genes.

Expression Profile of Two Storage-Protein Gene Families in Hexaploid Wheat Revealed by Large-Scale Analysis of Expressed Sequence Tags

“…Total DNA was isolated from seedlings of common wheat (T. aestivum cv CS) and from nullisomic-tetrasomic as well as ditelosomic lines of CS (Sears, 1965), as described previously (Ogihara et al, 1994). By tracing the SNP sites in the contigs, primer sets were designed using Primer3 software (Rozen and Skaletsky, 2000) so as to specifically amplify each multigene (Table II).…”

High-resolution RFLP map of the long arm of chromosome 5A in wheats and its synteny among cereals.

“…These inconsistencies found in wheat chromosomes were mainly due to the rearrangements involving chromosomes arms 4AL, 5AL, and 7BS in the polyploid wheats . The A genome of polyploid wheats was shown to be most closely related to that of T. urartu, showing differentiation from T. monococcum and T. boeoticum (Nishikawa, 1983;Dvorak et al, 1993;Takumi et al, 1993;Ogihara et al, 1994b). Actually, the hybrids between T. urartu and T. monococcum are sterile (Johnson and Dhaliwal, 1976).…”

“…Actually, the hybrids between T. urartu and T. monococcum are sterile (Johnson and Dhaliwal, 1976). On the other hand, the A genomes of T. monococcum (cultivated) and T. boeoticum (wild relative) were classified into one group due to the good crossability and chromosome pairing between the two species (Kihara et al, 1929) and their common molecular markers (Nishikawa, 1983;Dvorak et al, 1993;Takumi et al, 1993;Ogihara et al, 1994b).…”

Subfamily divergence in the multigene family of ribulose-1, 5-bisphosphate carboxylase/oxygenase (rbcS) in Triticeae and its relatives.

“…Exon 1 encodes a transit peptide of 46 amino acids plus 2 amino acids of the mature protein and exon 2 encodes the major part of the mature protein which consists of 127 amino acids (Broglie et al, 1983). Galili et al (1991) estimated that there were at least 22 copies of rbcS in the hexaploid wheat genome, while Ogihara et al (1994) reported the presence of approximately 100 copies. The wheat rbcS genes were classified into four subfamilies based on differences in the Southern hybridization pattern using the 3' non-coding region as probe (Galili et al, 1992).…”