II. 19. Gene symbols for barley high-lysine mutants.
Jens Jensen and Hans Doll. Agricultural Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark. "R"
A high-lysine barley is characterized by an increased content of the amino acid lysine of its seed protein compared to that of normal barley. The basic gene symbol lys and sex have each been proposed for the genes of the barley high-lysine mutants. Some arguments are given below for using the symbol lys.
The first high-lysine barley discovered was Hiproly (Munck et al. 1970). The increased lysine content of Hiproly is conditioned by a single recessive gene; it was suggested that this be designated lys referring to the increased content of lysine (Munck 1972). Furthermore, Munck (1972) mentioned that the symbol lys should be revised when the basic action of the gene is understood better. However, to change gene symbols every time we gain a better insight into a basic gene action would not be practical. Moreover, the Recommendation by the International Committee for the Nomenclature and Symbolization of Barley Genes point 2 (BGN, Vol. 2 page 12) states that the symbol should be as descriptive as possible of the phenotype. A gene symbol referring to the basic action of the gene would probably not be sufficiently descriptive. The second high-lysine locus was named lys2 by Eslick and Hockett (1976a).
After that time the consistency of the gene symbols for high-lysine mutants was over. Most of the high-lysine mutants have shrunken endosperms, and Ullrich and Eslick (1977, 1978b) proposed to designate the gene controlling the shrunken endosperm trait of the high-lysine mutant Risø 1508 sex3c. However, they stress the close association between the high-lysine trait and the shrunken endosperm, and they favor the explanation that the two traits are pleiotropic effects of one gene. Furthermore, they suggest different ways to suppress the shrunken endosperm trait while retaining the high-lysine content of the seeds (Ullrich and Eslick 1978a). If the high-lysine character is present in materials with plump seeds, which is a goal of many barley breeding efforts, the sex symbol will no longer be meaningful. It was proposed in another study that the high-lysine gene of Risø 1508 be designated lys3a and that its allelic genes, in Risø 18 and 19, be designate lys3b and lys3c, respectively (Jensen 1979a). The designation lys was advanced because the mutants were selected and best known for their increased lysine content, and also because the symbol lys was considered to have priority in that the similar gene in Hiproly was so designated (Munck 1972).
The genes responsible for the shrunken seed character of the high-lysine Risø mutants 8, 13, 29, and 86 were given the designation sex5g, sex4f, sex1e, and sex1d, respectively by Ullrich and Eslick (1978d). The high-lysine and shrunken endosperm characters of the high-lysine mutants 8, 13, 16, and 17 were found to be pleiotropic, controlled by their respective high-lysine genes (Jensen 1979b).
Six shrunken endosperm (sex or seg) mutants and one high amylose (amo1) mutant were reported as additional high-lysine mutants by Ullrich and Eslick (1978a). These mutants were selected apparently for the character indicated by their gene-symbols. One of these genes, sex1a, previously designated sex1f (Eslick and Hockett 1976b), was shown to be allelic with the genes on chromosome 6 of the high-lysine mutants 29 and 86, and non-allelic with the gene also located on chromosome 6 of the high-lysine mutant 13 (Ullrich and Eslick 1978c, 1978d). However, our studies have shown that the high-lysine gene of the mutants 13, 29, and 86 are allelic, and that they are allelic with the sex1a gene (Jensen 1979b). Besides those genes only one more high-lysine gene - that of Risø mutant 527 - is known to be on chromosome 6 (Jensen 1979b). This indicates that mutant 13 may have been interchanged with mutant 527. We do not know whether the mistake was done in our laboratory, or at Bozeman. However, we are willing to check doubtful samples by an analysis of their hordein composition by means of which we have been able to distinguish them.
As the genes controlling the high-lysine character in the mutants 13, 29, and 86 are alleles in the locus sex1, the high-lysine genes in those Risø mutants should carry the sex1 locus symbol as proposed by Ullrich and Eslick (1978c). The sex1a gene was selected probably for its shrunken endosperm trait; its locus was localized, and the sex1 symbol was proposed before any other alleles were known in that locus. We acknowledge therefore the priority of the sex1 symbol but we prefer a lys symbol in this case because we believe that it will prevent unnecessary confusion.
Shrunken endosperm and high-lysine content have arisen simultaneously in many mutants, and attempts to separate the two traits by recombination have apparently failed. Thus it appears safe to assume that the two characters are controlled by a single gene.
We therefore propose: 1) that the high-lysine gene of mutant Risø 1508, 18, and 19 be designated lys3a, lys3b and lys3c as previously proposed (Jensen 1979a); 2) that the high-lysine gene in Risø mutant 8 be designated Lys4d as this gene is dominant or semidominant (Jensen 1979b). Lys4d is located on chromosome 5 under the designation sex5g (Ullrich and Eslick 1978d) and, as far as we know, no other genes which might have high-lysine traits is known on chromosome 5; 3) the high-lysine gene of Risø mutant 13, 29, and 86 be designated lys5f, -g, and -h respectively, assuming that the genes all are allelic, and the sex1a gene be designated lys5e; and 4) the high-lysine gene in Risø mutant 527 be designated lys6i. The high-lysine genes of Risø mutants 16 and 17 are located on chromosome 1 (Jensen 1979b); they are not yet given a gene symbol as they may be allelic with localized and shrunken endosperm genes. The genes in the other known high-lysine mutants are not yet localized and also may be allelic with shrunken endosperm genes already located and designated. The proposed gene symbols are shown in Table 1.
Table 1. Proposed gene symbols for high-lysine mutants of barley.
References:
Eslick, R.F. and E.A. Hockett. 1976a. A second locus for high lysine barley. Barley Genetics III:634.
Eslick, R.F. and E.A. Hockett. 1976b. In: Description of genetic stocks. Barley Genetic Newsletter 6:140.
Jarvi, A.J. and R.F. Eslick. 1971. In: Description of genetic stocks in the barley genetic stock center at Fort Collins, Colorado. Barley Genetics Newsletter 1:193.
Jensen, J. 1979a. Location of a high-lysine gene and the DDT-resistance gene on barley chromosome 7. Euphytica (in press).
Jensen, J. 1979b. Chromosomal location of one dominant and four recessive high-lysine genes in barley mutants. In proc.: Int. Symp. of Seed Protein Improvement in Cereals and Grain Legumes. Neuherberg, Federal Republic of Germany, 4-8 Sept. 1978, IAEA (in press).
Munck, L., K.E. Karlsson, A. Hagberg, and B.0. Eggum. 1970. Gene for improved nutritional value in barley seed protein. Science 168:985-987.
Munck, L. 1972. High lysine barley - a summary of the present research development in Sweden. Barley Genetics Newsletter 2:54-59.
Ullrich, S.E. and R.F. Eslick. 1977. Inheritance of the shrunken endosperm character, sex3c of Bomi Risø mutant 1508 and its association with lysine content. Barley Genetics Newsletter 7:66-73.
Ullrich, S.E. and R.F. Eslick. 1978a. Lysine and protein characterization of spontaneous shrunken endosperm mutants of barley. Crop Science 18:809-812.
Ullrich, S.E. and R.F. Eslick. 1978b. Inheritance of the associated kernel characters, high lysine and shrunken endosperm, of the barley mutant Bomi, Risø 1508. Crop Science 18:828-831.
Ullrich, S.E. and R.F. Eslick. 1978c. Allelism evidence for barley high lysine, shrunken endosperm xenia (sex) mutants. Barley Genetics Newsletter 8:109-112.
Ullrich, S.E. and R.F. Eslick. 1978d. Chromosome location evidence for Risø induced high lysine shrunken endosperm mutants of barley. Barley Genetics Newsletter 8:114-125.
