II. Genic analysis, mutation and linkage

15. Two newly found aminopeptidase loci and allelic variation in Asian cultivars
        Xin-Li Sun1, Hong-Wei Cai1 , Ji-Chen Xu2 ,Li-Huang Zhu2 and Xiang-Kun Wang 1
        1) Dept. of Plant Genetics and Breeding, Beijing Agric. Univ., Beijing, 100094 China
        2) Institute of Genetics, Academia Scinica, Beijing, 100101 China
 

     Four isozyme loci coding aminopeptidase have been found by the starch gel system in rice. Using PAGE method, we found two new loci for AMP isozyme named Amp-5 and Amp-6(t).Amp-5 is a monomer, and its band migrates faster than Amp-l. Band.of Amp-6 (t) migrates slower than Amp-2 (Fig. 1 ). Mendelian segregation for Amp-5 was confirmed in F2 and double haploid (DH) lines (Table 1).
    In an Indica-Japonica (ZYQ/JX17) DH population, the linkage of Amp-5 with other isozyme loci and RFLP markers was examined. Amp-5 showed linkage with Est-2 (13cM) and CD017B (26cM) which are located on chromosome 6 (Fig. 2). Amp-3 was
also studied, which is known to be closely linked with Est-2 on chromosome 6 (Sano and Barbier 1985). Band of Amp-3 migrates slower than that of Amp-l and Amp-5, indicating that Amp-3 and Amp-5 have different loci.
    A total of 539 Asian cultivated rice varieties (273 Japonicas and 266 Indicas) were examined for their allelic variation at these loci as shown in Table 2. In addition to a null allele, four active alleles were found at Amp-5 locus. Amp-50 and Amp-51 were more frequent in Indica than in Japonica, while Amp-52 was frequently found in Japonica. Amp-6 (t)1 and Amp-6(t)2 were frequently found in Japonica and Indica, respectively.
 
Table 1. Segregation for Amp-5 in F2 and DH lines
Cross Generation 11 12 22 Total c2
130/221 ZYQ/JX17 F2
DH		 23
21

 

 26 
0		 29 
27		 78 
48		 9.59* 0.75

 
 
Table 2. Allele frequencies of Amp-5 and Amp-6(t)
Locus Allele No. of samples Indica Japonica Total
Amp-5 0 

1 

2 

3

 96 

73 

357 

13

 0.336 

0.210 

0.446 

0.008

 0.039 

0.059 

0.863 

0.039

 0.178 

0.135 

0.662 

0.025
Amp-6(t) 0 

1 

2

 5 

308 

226

 0.011 

0.248 

0.740

 0.004 

0.895 

0.098

 0.009 

0.572 

0.419

 


Fig. 2. Partial linkage map of chromosome 6 showing location of Amp-5.

References

Morishima, H. and J. C. Glaszmann, 1990. Current status of isozyme symbols. RGN 7: 50-57.
Sano, R. and P. Barbier, 1985. Analysis of five isozyme genes and chromosomal location for Amp-l. RGN 2:
        60-62.