19. Effects of genes Ef-1 and m-Ef-1 on free amino acid content in the leaves of Taichung 65

Ching-Min CHENG1, Nien-Tai HU1 and Kuo-Hai TSAI2

1) Agricultural Biotechnology Laboratory

2) Department of Agronomy, National Chung Hsing University, Taichunc, 40227 Taiwan, ROC

A gene for early flowering, Ef-1a (abbreviated as Ea) and its emphasizing gene, ma-Ef-1 (abbreviated as ma), were each isolated in isogenic lines of a rice variety, Taichung 65 (T65; Tsai and Oka 1966; Tsai 1985). Isogenic lines with Eb, an isoallele of Ea, were found to have higher seed protein content than T65 (Tsai 1982). Rice varieties differing in protein content were found to differ in amino acid content (IRRI 1970). To learn about free amino acid contents in the leaves, four isogenic lines with e m+ (=T65), e ma, Eam+ and Eama were examined in the summer crop season of 1986.

The sampling of leaves started from 35 days after seeding or 13 days after transplanting in the field. The leaves on the main stem of 15 plants of each line were sampled at four-day intervals, and after the 50th day at two-day intervals. The total content of free amino acids was determined by the ninhydrin reaction method. The contents of individual amino acids were determined by an LKB 4150 Alpha Amino Acid Analyzer with the 8th and 10th leaves.

The data for total amino acid content at different ages of respective lines (all lines assayed at the same time) are summarized in Table 1. The 39-day samples showed the highest value, and the content decreased with growth after that day. Lines with gene e had higher values than those with E at each time of assay. This may be considered as reflecting the primary effect of the genes.

Table 1. Free amino acid contents in the leaves of T65 and its early-heading isogenic lines sampled on different days after seeding, as shown by absorbance at 570 nm (equivalent to 90 p moles for one OD570)

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Days after seeding T65  T65(7)ma    T65(20)Ea    T65(20)Eama    
                   em+  e ma        Ea m+        Ea ma  
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35 (Aug. 18)     2.36      2.52       2.37         2.13
39               4.06      3.32       3.14         2.59
43               1.31      2.14       1.27         1.71
47               1.10      1.20       1.12         1.15
50               1.07      0.93       0.93         0.96
52               0.92      1.06       1.00         0.95
54               0.85      0.91       0.97         0.74
56               0.80      0.78       0.72         0.77
58               0.47      0.30       0.39         0.44
Mean             1.32a     1.33a      1.19b        1.16b  
LSD for lines,5% 0.06
              1% 0.08
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a, b-Differing at 1% level.

Fig. 1. Regression analysis of amino acid content (y) on days after seeding. The 39th days was taken as the first day.

 

Analysis of variance of the data showed that the differences due to lines, sampling days and their interaction were significant. Gene E/e had stronger effect on total amino acid than gene m/m+. When the data were converted into logari- thms, the regression of amino acid content on days after seeding, as shown in Fig. 1, had higher coefficients of determination than when the original data were used for computation.

The contents of individual amino acids in the 8th and 10th leaves of the main stem in T65 and T65(20)Ea are given in Table 2. Alanine had the highest value throughout the assays. Its content was taken as the standard (10.0) and the contents of other amino acids were shown by its relative values. When those amino acids were ranged in decreasing order of the content, the rank correlations between T65 and (20)Ea were 0.97 (8th leaf) or 0.96 (10th leaf), and those between the 8th and 10th leaves were 0.96 in T65 and 0.94 in (20)Ea, all being significant at 1% level. This indicates that these lines have similar compositions of free amino acids.

Table 2. Contents of 13 amino acids in the 8th and 10th leaves 
of T65 and its isogenic line, (20)Ea
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                    T65              T65(20)Ea  
Amino acid    _______________       ______________
               8th       10th       8th       10th
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Alanine*       10.0      10.0       10.0      10.0
               (=1081)  (= 622)    (= 799)   (= 537)
Arginine        1.20      0.53       0.80      0.54
Aspartic acid   1.81      2.35       1.91      2.31
Glutamic acid   4.29      8.74       4.91      8.04
Glycine         1.57      1.39       1.70      1.45
Isoleucine      1.52      1.69       0.82      1.40
Leucine         1.81      1.90       1.88      2.57
Lysine          0.95      1.12       0.73      1.14
Phenylalanine   1.04      0.81       0.69      0.71
Serine          8.35      4.35       4.42      4.15
Threonine       2.01      2.19       1.85      1.96
Tyrosine        0.61      0.20       0.53      0.61
Valine          2.68      2.57       1.99      2.01
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*unit in n mole/10 mg tissue. Each value was taken as 10.

References

IRRI, 1970. Improvement of the protein content of rice. Annual Report for 1969, p. 32-39.

Tsai, K. H., 1982. Effects of an earliness gene, Eb, on character expression in different rice varieties. J. Agric. Assoc. China 120: 42-64.

Tsai, K. H., 1985. Genic analysis of the emphatic gene, m-Ef, for early flowering in rice. J. Agr. Assoc. China 130: 1-15.

Tsai, K. H., and H. I. Oka, 1966. Genetic studies of yielding capacity and adaptability in corp plants, 2. Analysis of genes controlling heading time in Taichung 65 and other rice varieties. Bot. Bull. Acad. Sinica 7: 54-70.