Chromosome Arms 7DS Research Articles

The structure and genetic control of a new class of disulphide-linked proteins in wheat endosperm

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of unreduced total protein extracts from the endosperm of hexaploid wheat revealed three high molecular weight protein bands (triplet bands) in a zone of heavy background streaking. Electrophoretic examination of 135 hexaploid cultivars showed at least five different patterns of these triplet bands. Nine durum wheat cultivars showed a single band only. Analysis of nullisomic-tetrasomic and ditelocentric lines of 'Chinese Spring' wheat revealed that the slowest moving band (Tri-1) of the triplet was controlled by gene(s) on chromosome arm 1DS and the fastest moving band (Tri-3) by 1AS. The band with intermediate mobility (Tri-2) was found to be a hybrid aggregate of the subunits controlled by 1DS and 1AS. Using a non-reducing/reducing form of 2-dimensional (2-D) electrophoresis, these triplet bands were shown to be heterotetramers of four subunits designated D (M.W. 58,000), δ (22,000), A (52,000) and α (23,000) where Tri-1=DδDδ, Tri-2 = DδAα and Tri-3 = AαAα. With very low concentrations of 2-mercaptoethanol (ME), the tetramers dissociated into dimeric subunit pairs (Dδ, Aα), the monomers being observed with higher concentrations of ME. The structure of these subunit pairs resembles that of the subunit pairs in the globulin storage proteins of oats and some legumes. The 2-D method employed in this study was useful also for separating low molecular weight (LMW) subunits of glutenin from the monomeric gliadins which have similar electrophoretic mobility in 1-D separation. It was shown that at least four of these LMW glutenin subunits are controlled by genes on 1DS and 1AS and at least one subunit is controlled by gene(s) on 1BS. This electrophoretic separation method has proven useful in understanding the aggregation behaviour of the seed proteins of wheat.

The chromosomal locations of leaf peroxidase genes in hexaploid wheat, rye and barley

Eight leaf peroxidase isozymes were distinguished by IEF in 'Chinese Spring'. Two genes which control the production of three of these isozymes were located on chromosome arms 1BS and 1DS by nullisomic analysis. These loci probably form part of a homoeoallelic series and have been designated Per-B1 and Per-D1 respectively. Analysis of chromosome 1B short arm terminal deletion stocks indicated that the Per-B1 locus is located between the nucleolar organiser region and another isozyme marker, Hk-B1. Two variant leaf peroxidase phenotypes were distinguished in a small sample of hexaploid wheat varieties. Analysis of wheat-alien addition and substitution lines identified homoeologous loci in rye (Per-R1) and barley (Per-H1).

A comparative study of the changes of peroxidase patterns during wheat, rye, and triticale germination

A comparative study on the electrophoretic peroxidase patterns of rye (Secale cereale L.), tetraploid wheat (Triticum turgidum L. durum), hexaploid wheat (Triticum aestivum L.), and hexaploid Triticale during kernel germination has been carried out. Endosperm, embryo, coleoptile, and the first leaf have been analyzed. A drastic change in peroxidase patterns was observed during the first hours of germination in all the materials studied. The triticale peroxidase patterns were similar to tetraploid wheat female parent patterns. The chromosomal locations of two leaf peroxidase isozymes of hexaploid wheat 'Chinese Spring' are also reported. These two isozymes, C9 and C10, are associated with chromosome arms 3DS and 7DS, respectively.

The genetic control of hexokinase isozymes in wheat

SUMMARYIn extracts of mature wheat grains, 13 hexokinase isozymes were distinguished by IEF. The genes controlling the production of five isozymes were located on chromosome arms 1BS, 1DS and 3BS by nullisomic analysis. The three loci, part of two homoeoallelic series (Hk-1andHk-2) are designatedHk-B1,Hk-D1andHk-B2respectively. Analysis of chromosome 1D short-arm terminal deletions indicated theHk-D1locus to be located proximally to the glucose phosphate isomerase locus,Gpi-D1on the shortarm. Three variant HK phenotypes were distinguished amongst 55 hexaploid wheats examined. Analysis of seven Chinese Spring/Agropyron elongatumchromosome addition lines showed thatAg. elongatumisozymes were expressed in the wheat background in additions IV and V.

CHROMOSOMAL LOCATION OF GENES CONTROLLING FLAVONOID PRODUCTION IN HEXAPLOID WHEAT

Two-dimensional paper chromatography was performed on methanol extracts of leaves of hexaploid bread wheat, Triticum aestivum L. em. Thell. cultivar Chinese Spring, and of the available nullisomic-tetrasomic compensating lines, the tetrasomic lines and the ditelocentric lines. The chromatograms had 27 spots identified as flavonoids and six representing phenolic acids. Some of the areas were complex and contained more than one compound. Four flavonoids were identified as under the control of gene(s) on chromosome arms 1DS, 4DL, 5AS and 6BS. A phenolic glycoside was concluded to be controlled by a gene(s) on chromosome arm 7BL. Gene(s) on chromosome arm 4DL affected the amount of compounds in two other spots, and gene(s) on chromosome arm 4BS reduced the level of all flavonoid compounds. The individual compounds in some of the complex spots may be under the control of gene(s) on homoeologous chromosomes.

Identification of chromosome segments controlling the synthesis of peroxidases in wheat seeds and in transfer lines with Agropyron elongatum

The genes coding the synthesis of the three major cathodic isoperoxidases a, c, and d in common wheat cv. Chinese Spring, as determined by polyacrylamide slab gel electrophoresis, are located on the chromosome arms 7DS, 4BL, and 7AS, respectively. Transfer lines with Agropyron elongatum can be detected by electrophoretic analysis of peroxidases if the chromosome arm 7AgS is involved in these transfers. Results have also shown a homology between the chromosome 7D of common wheat and the chromosome 7Ag of Agropyron elongatum.

Nucleolar behaviour in Triticum

The maximum number of major nucleoli (macronucleoli) per nucleus of hexaploid, tetraploid and diploid wheat, Aegilops speltoides and Ae. squarrosa corresponded to the number of satellited chromosomes of each species. Smaller nucleoli (micronucleoli) were rare or absent in all of these species except the hexaploid, in which they were predominantly organized on chromosome arm 5Ds. — Fewer than the maximum number of macronucleoli in a mitotic interphase nucleus resulted from fusion of developing nucleoli. Enforced proximity of nucleolus-organizing regions resulted in more frequent fusion of nucleoli. — Analyses of related interphase nuclei showed that nucleoli, and hence probably chromosomes, undergo limited movement during mitotic interphase. These observations also indicate that specific chromosomes do not occupy specific sites in the interphase nucleus.