ESTIMATES OF GENOTOXIC EFFECT BY THE ANALYSIS OF MALE GAMETOPHYTE GENERATION OF VINES
Nebish A.A.
Laboratory of General Biology, Department of Genetics and Cytology,
Yerevan State University, Yerevan, Armenia
Introduction
The process of in situ indication of genotoxicity requires well-founded selection of indicator species to obtain a reliable indicator of the genotoxic potential in the examined locality or region.
One of advantages in using pollen grains as bioindicators of mutagencity is the high sensitivity conditioned by the haploid state, when all lethal mutations affecting the development of pollen are immediately evident (Micieta and Murin, 1995). The pollen abortion assay reflect deletions in virtually any part of the genome. However, the greatest advantage is that the species live in the polluted environment under evaluation, and this makes possible to evaluate the effectiveness of ecological factors including pollution components (Constantin,1984).
For such research are very convenient the sorts of Vitis vinifera with low level of sterility. Some minimal sterility of pollen is detected even in normal functional anthers. It can be the result of abnormal distribution of chromosomes in meiosis. Lyakh (1995) presented interesting hypothesis about the evolutionary consequences of decrease or absence of concurrence between microgametophytes. In that case in the population arrive many new non-typical forms, that can be positive for the preservation of the species in the changing conditions of the environment.
Male gametophyte generation of vines can be applied as bioindicators of genotoxicity (Ma, 1979). The pollution of the environment with technogenic factors can change the evolutionary formed complexes of adaptive reactions. In situ indication of genotoxicity requires well-founded selection of indicator genotypes to estimate genotoxic potential in the examined locality or region (Micieta and Murin,1995).
The reasons of formation of abortive pollen can be different. They can include the regulatory role of tapetum, RNA, i-RNA, intensity of all synthetic processes. Pederson et al (1987) mentioned the difference in the gene expression on the different stages of formation and functioning of the pollen. In the species with three-cell pollen the genes can be expressed on both stages, and in two-cell pollen most of the genes are expressed during the pollen formation.
Penetration of different types of irradiation (UV, gamma, X-rays) varies in species, depending on the size and shape of the pollen grain, and the thickness of the pollen wall (Gilles, Prakash, 1987). Low levels of normal pollen bring to low fertilization and abnormal seeds development.
One of mentioned approaches, allowing to estimate the genotoxic action of environmental factors, is the test for the definition of plants pollen grains fertility. Flowering plants have been used as bioindicators of mutagenicity, phototoxicity and genotoxicity of environmental pollutants. Pollen grains fertility parameter for any kinds of plants including fruit trees, allows to estimate gametocide effects of environmental mutagens. Thus, it is reasonable to use those kinds of plants that proceed in the investigated environment sporophyte and gametophyte cycles of development.
Materials and Methods
The complex analysis of male reproductive system of vines growing on distance of 3-5 km from the Armenian Nuclear Power Plant (ANPP) near the settlement Metsamor, in comparison with the control point on distance more than 30 km from ANPP is realized. Investigated 10 sorts of vines are Charentsi, Meghrabuyr, Nerkarat, Burmunk, Shahumyani, Kishmish black, Kishmish white, Ararati, Arakseni, Hadisi. Biometric parameters of pollen are investigated by the method of the acetocarmine preparations analysis. In the fertile grains the cytoplasm is colored dark carmine-red. The sterile pollen grained are not stained or are stained non-uniformly. The data obtained on the basis of analysis of large quantities of pollen grains (about 10000 in each variant).
Results and Discussion
The results presented in Table provide evidence for a high level of pollen fertility in investigated sorts of vine. The highest level of pollen fertility discovered for sort Nerkarat (in control 98.84 ± 0.11%, in experiment 97.62 ± 0.15%). The data on sorts Charentsi, Meghrabuyr, Nerkarat, Burmunk, Kishmish black, Arakseni, Hadisi are shown the fertility level more than 87% in both points of experiments. Analysis of the male gametophyte of vines confirmed a higher quality of the pollen population.
Table. Properties of pollen fertility in vines in different points of growth
Metsamor / Control point
Charentsi / 95.36 ± 0.21 / 95.16 ± 0.21
Meghrabuyr / 90.60 ± 0.29 / 90.80 ± 0.29
Nerkarat / 98.84 ± 0.11 / 97.62 ± 0.15
Burmunk / 96.60 ± 0.18 / 97.69 ± 0.15
Shahumyani / 89.96 ± 0.3 / 72.36± 0.45
Kishmish black / 98.0 ± 0.14 / 97.34 ± 0.16
Kishmish white / 87.67 ± 0.33 / 84.90± 0.36
Ararati / 69.55 ± 0.46 / 96.8 ± 0.18
Arakseni / 87.70 ± 0.33 / 96.92 ± 0.17
Hadisi / 97.03 ± 0.17 / 94.17 ± 0.24
Conclusion
The obtained results demonstrate high fertility of pollen of investigated sorts of vines growing around the area of ANPP, that significantly not differs from the control point. Thus, the influence of the ANPP on the male generative system of the investigated sorts of vines is not revealed.
The further monitoring of pollen fertility is necessary at the different plants species, growing around the area of ANPP, for the definition of their suitability for bioindication of action of environment factors.
References
1. Giles L.K., Prakash P.J. Pollen cytology and development. International Review of Cytology. 1987, 5, p. 107-151.
2. Ma Te-Hsiu. Micronuclei induced by X-rays and chemical mutagens in meiotic pollen mother cells of tradescantia. Mutation Research, 1979, 64, p.307-313.
3. Micieta K., Murin G. Microspore analysis for genotoxicity of a polluted environment. Environmental and Experimental Botany, 1995, vol. 36, N 1, pp. 21-27
4. Pederson S., Simonsen V., Loeschcke V. Overlap of gametophyte and sporophytic gene expression in barley. Theor. And Appl. Genet., 1987, 75, p. 200-206.