Acid phosphatase isozymes in root, coleoptile and callus tissues of inbreds and their hybrids

--A. Kumar, H. Kumar, V. K. Shahi and S. K. T. Nasar

Isozymes of acid phosphatase were studied under different developmental stages, such as root and coleoptile, in vivo and at the callus stage in vitro in 5 inbreds, Tuxp162-1, Tuxp237-2, Tuxp104-2, MS1DR-120, PKMS1-49, and 4 hybrid genotypes, Tuxp162-1xTuxp237-2, Tuxp237-2xTuxp124-1, Tuxp104-2xTuxp46-6, MS1DR-120xPKMS1-49.

In all, 8 different isozymes were found in maize root, coleoptile and callus tissues. Based on their mobility towards the anode, these isozymes were numbered as A-1 to A-8 starting from the origin. These isozymes were distributed in 4 electrophoretically different zones named (i) AP-1 having isozyme band A-1, (ii) AP-2 having isozyme bands A-2 to A-4, (iii) AP-3 having isozyme bands A-5 to A-7 and (iv) AP-4 having isozyme band A-8.

Coleoptile tissues had zones AP-1, AP-2 and AP-3. The AP-4 zone was present only in callus tissues with AP-1 and AP-2 zones. Roots had only AP-2 and AP-3 zones.

Coleoptile tissues of inbreds Tuxp162-1, Tuxp237-2 and their hybrid had identical isozyme bands showing the same isozyme pattern, but they differed in the intensity of isozyme activity. Similar observations were found with inbreds MSDR1-120, PKMS1-49 and their hybrid. Hybrid Tuxp237-2xTuxp124-1 had different bands than its parent Tuxp237-2, while hybrid Tuxp104-2xTuxp46-6 showed similar bands to those shown by one of its parents, Tuxp104-2. However, the intensity of activity of isozymes was different.

The isozyme pattern of callus tissues was different than that of coleoptile tissues. Inbreds Tuxp162-1, Tuxp237-2 and their hybrid had the same bands, except for the absence of the A-8 band in the latter inbred and a difference in intensity of bands. A-8 was a new isozyme band not found in coleoptile and root tissues.

Isozyme pattern of root tissues in the inbreds MS1DR-120, PKMS1-49 and their hybrid differed in bands as well as in the intensity of identical bands.

On overall comparison, it has been found that: (i) the maximum number of isozymes was expressed in the coleoptile tissues; (ii) not only fewer isozymes were present in the calli grown in vitro, but their mobility and intensity were also markedly different; (iii) a new band, A-8, appeared in the calli of only two genotypes; and (iv) a uniform pattern of isozyme expression as was found in coleoptilar tissues was not obtained in the case of calli.

The study has shown that the genotypes under consideration were closely related with respect to acid phosphatase enzyme. In no case was a total absence of acid phosphatase enzyme observed. In coleoptiles, variation in electrophoretic mobility between parents and hybrids has not been seen. This was indicative of homozygosity at the acp loci. A marked difference in the isozyme number and mobility in calli compared to their callusing explant and nonavailability of band A-8 in in vitro tissues was due to activation of an otherwise normally repressed locus due to genotype x tissue culture interactions.

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