All-Union Inst. Agric. Biotechnology

Esterase and peroxidase patterns in leaves of A188 somaclones

--Emil E. Khavkin

Fully developed 4th and 5th leaves of light-grown seedlings were employed for zymographical analysis of SC2 generation in eight somaclonal variants described in the note by Dolgykh et al. (MNL, this issue). Variable bands of anodic esterases (marked by arrows in Fig. 1A and B) could be tentatively assigned to E5, E7, E9 and E4 loci and non-identified bands 42/43 and 59 as described by MacDonald and Brewbaker (Hawaii Agr. Exp. Sta. Tech. Bull. No. 89, 1975). Among anodic peroxidases (Fig. 2A) variable bands appeared immediately following the most mobile zone described as PRX6 by Brewbaker and Johnson (MNL 46:29, 1972) and between two slowly moving zones assigned to PRX3 and PRX7, this interval could be tentatively identified as PRX9 and PRX10 zones. Only quantitative changes in staining were found in the cathodic peroxidase spectrum (Fig. 2B).

Two features of these isozyme patterns fall in line with our previous observations made with inbred 346 somaclones (MNL 64:91, 1990). First, the extent of variation found within several samples of sibs produced from the same SC1 ear (e.g., in the case of somaclones 11, 15, 27, 53 or 54b) sometimes exceeded the deviation from the standard (control, A188). Second, some of the bands active in somaclones but absent from the leaves of the standard were previously described by Brewbaker et al. not as leaf-specific but as characteristic of other tissues, e.g., root-specific E4 or root-, coleoptile- and mesocotyl-specific PRX9 and PRX10. It is also noteworthy that in both inbreds some loci seemed to be more sensitive to somaclonal variation and affected more frequently than others: virtually the same organ-specific anodic esterases and peroxidases exhibited significant changes in contrast to invariant non-specific isozymes, e.g., E8 or PRX3.

These observations, along with our earlier data on isozyme patterns of intact and isolated tissues (Biochem. Physiol. Pflanzen 174:431, 1979; MNL 55:47, 1981), suggest that there is a specific control system ordering tissue- and organ-specific isozyme spectra that might be affected by somaclonal variation at the early steps of a regulatory cascade ruling cell and tissue differentiation. By misgoverning some of temporal and spatial signals for isozyme loci expression, somaclonal variation could produce numerous, apparently non-linked (judging by sibs) and probably non-heritable, changes in isozyme patterns.

Figure 1. Esterase patterns of control (C) and somaclone leaves as resolved by PAGE after Davis (A) and Taber and Sherman (B).

Figure 2. Peroxidase patterns of leaves as resolved by PAGE after Davis (A) and Reisfield et al. (B).

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