BGN 8: Inheritance of aminopeptidase and endopeptidase isozymes in barley BARLEY GENETICS NEWSLETTER, VOL. 8, II. RESEARCH NOTES
Díaz, pp. 31-34

II. 8 Inheritance of aminopeptidase and endopeptidase isozymes in barley.

Daniel G. Díaz. Departamento de Genetica, C.I.C.A.-I.N.T.A. C.C. 25, 1712 Castelar, Argentina. "R"

The inheritance of the isozymes of aminopeptidase and endopeptidase, the enzymes that can hydrolise L-Leucil beta-Naphthylamide and alpha-N-Benzoyl-DL-Arginine-beta-Naphthylamide, respectively, has been studied by means of starch gel electrophoresis techniques in barley seedlings. A single buffer system and staining method was used for both enzymes, thoughout these experiments, while different sustrates were utilised to recognise the isozymes (Scandalios, 1969).

Three isozymes presenting each a distinct zymogram, were found for aminopeptidases (Figure 1). The inheritance of bands A and C was studied in the F1 and F2 generations of several crosses: Triple Awn Lemma x Cebada Negra, M.C.90 x Cebada Negra, Hordeum spontaneum x C.I. 4220-2. It has been observed that each band is controlled by the presence of a gene pair, referred to as Amp-A and Amp-C. Each gene has two alleles, 1 and 0, the former representing the band, and the latter denoting the absence of such a band (null allele). Table 1 shows that Amp-Al and Amp-Cl are dominant over their null alleles Amp-A0 and Amp-C0, and the adjustment to a 3 : 1 ratio is statistically satisfactory. Band A and band C are inherited independently (p = 0.30). The locus Amp-A is linked to gene Nn (Naked seed) in chromosome 1, and also to a gene controlling anthocyanin production in seedlings derived from H. spontaneum. The latter character has been tentatively called Plm (red seedling). No tests have been carried out to demonstrate the homology of Plm to the Rs (red stem) gene, previously determined by Briggs and Stanford (1943) also in chromosome 1. The order of the three genes, and the distances between them, in a three-point experiment, are given below.

Figure 1. Aminopeptidases zymograms. 1) M.C. 90 and C.I. 4220-2. 2) Triple Awn Lemma and H. spontaneum. 3) Cebada Negra.

Table 1. Adjustment to a monogenic segregation in the F2 generation of the Amp-A and Amp-C genes using the G statistics. The expected ratio is 3:1; df 1.

Furthermore, the Amp-A gene is inherited independently from Trtr (triple awned lemma, in chromosome 2), Vv (row number, in chromosome 2), Bb (black lemma and pericarp in chromosome 5), Ml-m/a/c (Mildew reaction in chromosome 5), and Btbt (brittle rachis from H. spontaneum); Amp-C, in turn is inherited independently from Trtr, Bb, Vv, Ml-m/a/c, and ml-o (mildew reaction in chromosome 4).

Endopeptidases present two zymograms having two bands in both homozygous genotypes (Figure 2). In the F3 generation of crosses C.I. 4220-2 x Retu, C.I. 4220-2 x Maltería Heda, and Engledow India x C.I. 4220-2, it was found that the fast and slow zymograms were codominant, and their genetic behaviour indicates the presence of a single gene pair (Table 2). This gene, which was called Edp-A, has two alleles, Edp-Al and Edp-A2, representing the fast and slow patterns, respectively. It should be noted, however, that the Osiris barley variety showed no band for this enzyme. Edp-A is inherited independently from genes Nn, Vv, Ml-m/a/c and Ml-z (mildew reaction in chromosome 5).

Figure 2. Endopeptidases phenotypes. 1) Fast zymogram (Retu, Maltería Heda and Engledow India). 2) Zymogram of the heterozygote. 3) Slow zymogram (C.I. 4220-2).

Table 2. Adjustment to a monogenic segregation in the F3 families of the Edp-A gene, using the G statistics. The expected ratio is 1:2:1; df 2.
 

References:

Briggs, F. N. and E. H. Stanford. 1943. Jour. Agr. Res. 66: 1-5.

Scandalios, J.G. 1969. Biochem. Gen. 3: 37-79.

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