Protein Polymorphisms in the Quail Lines Selected for Large and Small Body Weight

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1 123 << Research Note>> Protein Polymorphisms in the Quail Lines Selected for Large and Small Body Weight Sri Murni ARDININGSASI, Yoshizane MAEDA, Shin OKAMOTO, Satoru OKAMOTO1) and TSutomu HASHIGUCHI Department of Animal Science, Faculty of Agriculture, Kagoshima University, Kagoshima 890 1) Department of Biological Resources, Faculty of Agriculture, Saga University, Saga 840 Protein polymorphisms were screened for 10 polymorphic loci in two lines of Japanese quail, selected for high (LL) and low (SS) body weight respectively, during 57 generations, and a random bred control line (RR). The Hb-1 locus of the 10 loci was fixed in Hb-1B gene in all lines. The gene frequency of Es-DF was high in LL and low in SS. In the 6-PGD locus, although LL and RR lines showed the highest frequency in 6-PGDC, SS line was the highest (0.60) in 6- PGDD. The 6-PGDA allele was absent in SS line. The average heterozygosities based on 9 polymorphic loci of the LL, RR and SS lines were 0.410, and 0.417, respectively. Inbreeding coefficient of LL and SS lines calculated as the degree of heterozygosity loss to RR line were 9.7% and 8.1%, respectively. The value of subdivision index (GST) was estimated The genetic distance value between RR and LL and between RR and SS were about and 0.020, respectively. Although differentiation of allele frequencies among lines was found at the Es-D and 6-PGD loci, the data of inbreeding coefficient, subdivision index and genetic distance indicate that the degree of differentiation among the LL, RR and SS lines is small. (Jpn. Poult. Sci., 30: , 1993) Key words: protein polymorphisms, Japanese quail, selected line, heterozygosity Introduction Japanese quail lines selected for large body weight (LL) and small body weight (SS), and a random bred control line (RR) reached the body weights of 197g, 60g and 101g for male at the 57th generation at 6 weeks of age (OKAMOTO et al., 1989). MAEDA et al. (1986, 1992) demonstrated that the muscle protein degradation rate, body temperature and the O2 consumption in SS line were higher than those of RR and LL lines. Recently, MAEDA et al. (1991) reported that high rate of muscle protein degradation in SS line was related to their high activity of calcium activated neutral protease and low activity of its inhibitor. It is very interesting to assess the difference of protein polymorphisms among these strains with different physiological function. MAEDA et al. (1980) examined a heavy strain developed in the United States and found differences in allelic frequencies of plasma amylase and esterase-d corresponding to male body weight. Recently, CHANG et al. (1992) examined a Received Jul. 6, 1992

2 124 Jpn. Poult. Sci., 30 (2), 1993 comparison of genetic variability in strain of Japanese quail selected for heavy body weight and found that 1) the proportion of polymorphic loci was higher in the heavy strain than in the random bred strain, and 2) the heavy strains also differred from the random bred strain in the allelic frequencies of liver esterase and phosphogluconate dehydrogenase. These results suggest that some polymorphic loci in Japanese quail reflect allelic difference in selective adaptation for body weight. The present study was conducted to clarify the differences of the gene constitution and heterozygosity among quail lines selected for 6-week body weight. Materials and Methods Two selected lines used in this study were the large line (LL) and the small line (SS) which had been selected through 57 generations for increasing or decreasing 6-week body weight. The control line (RR) was a closed population maintained by random breeding over a 20-year period at Saga University. Within each line, one male and one female without common ancestor during the previous three generations were mated to reproduce the subsequent generation. There were 20 `25 matings in each line per generation. Ten protein loci were screened for the genetic variation by starchor agar- gel electrophoresis (Table 1). Gene frequencies were calculated by the direct counting method. The average heterozygosity (H) for all detected loci was estimated as the expected proportion of heterozygosity per locus, using the following formula: H=2nƒ (1-qi2)/(2n-1) where qi is the frequency of the ith allele at a locus, n is the number of individuals of the population and the bar means the average over all the loci examined. The relative inbreeding coefficients (F) of the LL and SS lines were calculated by the following formula: FLL=(HRR-HLL)/HRR FSS=(HRR-HSS)/HRR The relative magnitude of gene differentiation among strains was estimated by the coefficient (GST) of gene differentiation, GST=(HT-HS)/HT (NEI, 1973). Where Table 1. List of protein for examined for polymorphisms

3 ARDININGSASI et al.: Protein Polymorphisms of Japanese Quail 125 HT and HS are the average heterozygosities of the total population calculated from average gene frequencies of strains and a mean of average heterozygosity of strain, respectively. The genetic distance was calculated by NEI'S formula (NEI, 1972) modified by MULLER and AYALA (1982) for small population. Dr=-loge(Jxy/JxJy) where Jx, Jy and Jxy are the averages of (2nxXi2-1)/(2nx-1), and XiYi over the r loci studied, respectively. the ith allele at one locus in X and Y populations, (2nyYi2-1)/(2ny-1) The Xi and Yi are the frequencies of and nx and ny are the number of individual sampled from X and Y populations, respectively. The locus fixed in one gene in all strains was excluded for calculations of heterozygosity per locus, relative inbreeding coefficient, GST and genetic distance. Results Gene frequencies of 10 loci are given in Table 2. The gene frequencies at Amy, Alb, Hb-1, PGM-1, PGM-2, ADH and Es-2 loci were similar among three lines. locus of SS line was fixed in AmyA, and Hb-1 locus was fixed in Hb-1B in all lines. high frequency Amy Alb locus in the LL line was fixed in AlbQ1. For Es-D locus, LL line showed (0.583) of Es-DF, whereas the SS line showed low frequency (0.367) of Es-DF. In 6-PGD locus, although LL and RR lines showed the highest frequency of 6-PGDC, SS line was highest (0.60) in 6-PGDD. SS line. And 6-PGDA allele was absent in the Average heterozygosities of LL, RR and SS were calculated as 0.410, and 0.417, respectively. Inbreeding coefficient of LL and SS lines were estimated as 9.7% and 8.1%. The values of HT, HS and GST were calculated as 0.435, and 0.018, respectively. The genetic distance among three quail lines selected for body weight are given in Table 3. Genetic distance values between RR and LL and between RR and SS lines were about and 0.020, respectively. Discussion The gene frequency of Es-DF was high in LL and low in SS. These results were same to P line quail selected during 47 generations for 4-week body weight at University of Georgia (MAEDA et al., 1980). The relative inbreeding coefficients (FLL=9.7% and FSS=8.1%) of LL and SS lines were lower than those expected, and were marked much lower than that (F=31%) of P line (MAEDA et al., 1980). The difference of relative inbreeding coefficient between our quail lines and P line (MARKS, 1978) may be related to the mating system during the selective breeding in some degree. In the case of P line, the female was assinged randomly to individual males, with the restriction that full- or half-sib mating were not permitted. In contrast, the LL and SS lines have been selected under the restriction that matings were permitted only between male and female not having a common ancestor for the previous 3 generations. This restriction of mating might have prevented the increase in the inbreeding coefficient. CHANG et al. (1992)

4 126 Jpn. Poult. Sci., 30 (2), 1993 Table 2. Gene frequencies at 10 loci in three lines of quail selected of large (LL) or small (SS) body weight or were randomly bred (RR) n: number of birds Table 3. Matrix of genetic distance between respective pair of 3 lines based on 9 loci calculated by NEI'S formula equation (1972) compared the gene constitution among two large body weight strains and one random bred strain which were from genetically different origin in each other, and found that the proportion of polymorphism and expected heterozygosity value of the heavy strains were slightly higher than those of random bred strain. Higher value of heterozygosity

5 ARDININGSASI et al.: Protein Polymorphisms of Japanese Quail 127 selected strain compare to random bred differed from MAEDA et al. (1980) and the present study. The low value of GST (subdivision index) in the present study suggest that in spite of the differentiation of physiological character among three lines, the degree of differentiation among three lines in protein polymorphisms is small. The GST values based on the data of CHANG et al. (1992) were calculated as This value is larger than our data and suggests that the degree of differentiation strain is large. of the One of the reason of large values of GST of UBC strains may be that among the respective strains, the strains are from genetically different origin. Although differentiation of allele frequencies among lines was found at the 6-PGD and Es-D loci, the data of inbreeding coefficient, subdivision indicate that the degree of differentiation of LL, RR and SS lines is small. Acknowledgment index and genetic distance Authors wish to express our thanks to Miss Tanja BACH, International exchange advisor of Kagoshima City, Kagoshima Prefecture, for her reading of the manuscript. References CHANG, K.M., M. KIMURA and S. FUJII (1992) A comparisons of genetic variability in strains of Japanese quail selected for heavy body weight. Journal of Heredity, 83: CLAYTON, J.W. and D.N. TRETIAC (1972) Amino-citrate buffer for ph control in the starch gel electrophoresis. Journal of The Fisheries Research Board of Canada, 29: FERGUSON, K.A. and A.L. WALLACE (1961) Starch gel electrophoresis of anterior pituitary hormones. Nature, 190: HASHIGUCHI, T., M. YANAGIDA, Y. MAEDA and M. TAKETOMI (1970) Genetical studies on serum amylase isozyme in fowls. Japanese Journal of Genetics, 45: HOPKINSON, D.A., M.A. MESTRINER, J. CORTNER and H. HARIS (1973) Esterase-D: a new human polymorphisms. Annales Human Genetica. London, 37: MAEDA, Y., T. HASHIGUCHI and M. TAKETOMI (1975) Genetic variation of hemoglobin in Japanese quail. Japanese Journal of Genetics, 50: MAEDA, Y., T. HASHIGUCHI and M. TAKETOMI (1976) Genetic variation of acid phoshatase isozyme in Japanese quail, Coturnix coturnix japonica. Japanese Journal of Genetics, 51: MAEDA, Y., T. HASHIGUCHI and M. TAKETOMI (1978) Some associations of liver esterase-2 (Es-2) phenotype with economical traits in Japanese quail. Bulletin of Faculty of Agriculture Kagoshima University, 28: MAEDA, Y., K.W. WASBURN and H.L. MARKS (1980) Protein polymorphism in quail population selected for large body size. Animal Blood Groups Biochemical Genetics, 11: MAEDA, Y., K. HAYASHI, T. HASHIGUCHI and S. OKAMOTO (1986) Genetic studies on the muscle protein turnover rate of coturnix quail. Biochemical Genetics, 24: MAEDA, Y., K. KAWABE, S. OKAMOTO and T. HASHIGUCHI (1991) Genetical studies on muscle protein turnover rate and calcium activated neutral protease activity in skeletal muscle of Japanese quail, Coturnix coturnix japonica. Animal Science and Technology, 62: MAEDA, Y., Y. FUKUNAGA, S. OKAMOTO and T. HASHIGUCHI (1992) The changes of body temeratures, oxygen consumption, carbonic acid gas production and muscle protein turnover rate by selection for body size in Japanese quail. Comparative Biochemistry and Physiology, 103A:

6 128 Jpn. Poult. Sci., 30 (2), 1993 MARKS, H.L. (1978) Long-term selection for four-week body weight in Japanese quail under different nutrition environments. Theoretical and Applied Genetics, 52: MULLER, M.D. and F.J. AYALA (1982) Estimation and interpretation of genetic disance in empirical studies. Genetical Research, 40: NEI, M. (1973) Genetic distance between population. The American Naturalist, 106: NEI, M. (1983) Analysis of gene diversity in subdivided populations. Proceedings of the National Academy of Sciences of the United States of America, 70: OKAMOTO, S., S. KOBAYASHI and T. MATSUO (1989) Feed conversion to body gain and egg production in large and small Japanese quail line selected for 6-week body weight. Japanese Poultry Science, 26: SHOW, R.C. and R. PRASAD (1970) Starch gel electrophoresis of enzyme. A compilation of recipes. Biochemical Genetics, 4: