Heritable effects of 5-azacytidine treatments on the growth and development of flax (Linum usitatissimum) genotrophs and genotypes

Seed of flax (Linum usitatissimum) were treated for short durations with 5-azacytidine and the direct and heritable effects of the treatments on plant growth and development in general and, more specifically, on the contrasting phenotypes of Durrant's large and small genotrophs were examined. 5-Azacytidine induced a reduction in the height of the plants grown from treated seed. Twenty-two percent of the first generation progeny of these plants also had short phenotypes and, in most cases, the short phenotype was stably and uniformly inherited by the second generation progeny of the short, first generation plants. Treatment also induced a marked decrease in the flowering age in a few of the first generation plants that was also transmitted to their second generation progenies. The effects seen in the progeny generations suggest that most, if not all, of the heritable changes induced by the treatment are epigenetic. Several differences were seen between the large and small genotrophs, which indicate that the genome of the small genotroph is less susceptible, than the genome of the large genotroph, to 5-azacytidine induced heritable alterations.Key words: flax genotrophs, 5-azacytidine, height, flowering.

Peroxidase activity and relative mobility at anthesis in flax genotrophs and their F2 progeny: developmental and genetic effects

The genetic regulation of the environmentally induced heritable difference in peroxidase activity between Durrant's large (L) and small (S) flax genotrophs was examined in leaves from plants ranging in developmental age from 6 days before anthesis to 3 days after. Mean peroxidase activity was higher for S than L and intermediate for the reciprocal F2's from L × S and S × L crosses (F2L × S and F2S × L). However, activity increased with development and, since there were small but significant differences in the average developmental ages of L, S, F2L × S, and F2S × L plants, the effects of development on activity had to be taken into account in examining the F2 activity data for segregation. A regression method was used to remove developmental effects and, underlying these effects, total peroxidase activity appeared to be regulated by a single locus with two alleles and L dominance. Two other dimorphic loci, both described previously, were also examined. One regulates the presence-absence of septa hairs in the seed capsules and the other the relative mobility of anionic peroxidase isozymes. There was no phenotypic linkage between the three segregating parameters. The genetic control of activity appeared to regulate cationic rather than anionic activity. In addition, a relationship between activity and plant height indicated either that peroxidase activity is one of the factors regulating main stem elongation or that the locus regulating peroxidase activity is linked to one of the loci involved in the regulation of plant height.Key words: flax genotrophs, peroxidase, genetic control, development.

Genetic control of environmentally induced DNA variation in flax genotrophs

Heritable changes can be induced in the amount of nuclear DNA of the Stormont Cirrus variety (PL) of flax when grown in the specific environments of nitrogen and phosphorus, but such changes did not occur in variety Royal (R). Changes occurred in the amount of nuclear DNA of R when the PL nuclear and cytoplasmic factors were introduced by crossing. In the experiments reported here, tests were made on the plasticity of the F1's of their reciprocal crosses to PL and R to understand why L and S genotrophs are stable. The results suggest that there may be a feedback from nucleus to cytoplasm in L0, which inactivates the cytoplasmic factor. Possibly a paramutation-like mechanism adjusts the different amount of DNA, or heterochromatin, between the homologous chromosomes in heterozygotes. L3 and S3 DNA has reverted to the same amount as in PL. This reversion in DNA appears to be accompanied by an increase in stability rather than in any gain in plasticity. Key words: environment, flax, genotrophs, DNA variation.

Evidence for heterogeneity in the carbohydrate moieties of peroxidase isozymes from two environmentally induced flax genotrophs

The corresponding isoperoxidases from the flax genotrophs L and S have different molecular weights. Utilizing affinity chromatography on Sepharose-bound concanavalin A, we have shown that this lectin has a stronger affinity for the isoperoxidases purified from S stem tissue than those from L. The presence of differences in the carbohydrate composition of L and S peroxidases was confirmed when it was observed that only S peroxidases were susceptible to digestion by endo-β-N-acetylglucosaminidase H. Glycoprotein-enriched fractions were then purified from L and S stem tissue. The results showed that most glycoproteins of S origin have higher molecular weights than their L counterparts. Certain glycoproteins were digested by endo-β-N-acetylglucosaminidase H only if they were of S origin, while others were digested regardless of their origin. In both cases, the original differences in molecular weight between L and S glycoproteins were eliminated. These results support our view that posttranslational modification at the level of the carbohydrate chains of the L and S peroxidases is the reason for their heterogeneity on polyacrylamide gels.

DNA variation in flax tissue culture

The DNAs from leaves and callus from a series of flax genotrophs have been compared. The probes used for this comparison represent all of the highly repeated DNA sequence families in the flax genome. The abundance of most of the families could vary in culture, but the extent of variation was dependent on the genotroph. The extent of the variation observed between leaf DNA and callus DNA from a single genotroph was greater than that observed between the genotrophs in vivo. The DNAs from the progeny of a number of regenerated plants were also compared. They sometimes differed both from the callus from which the plants were regenerated and the original line from which the callus was derived. Individual progeny from a single inbred regenerated plant also differed.Key words: flax, DNA variation, somaclonal variation.