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Genetika - UDC 575.117 Original scientific paper GENE...

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UDC 575.117 Original scientific paper GENE REGULATION AND ITS ROLE IN HYBRID VIGOR AND STABILITY OF PERFORMANCE. Athanasios S. TSAFTARIS, Alexios N. POLIDOROS, and Eleni TANI Department of Genetics and Plant Breeding, Aristotelian University of Thessaloniki, 54006 Thessaloniki, Greece Athanasios S. Tsaftaris, Alexios N. Polidoros, and Eleni Tani (2000): Gene regulation and its role in hybrid vigor and stability of per- formance. –Genetika, Vol32, No.3, 189-201 Recent biochemical and molecular investigations on heterosis indicate that quantitative variation of gene expression may be important in vigor manifestation. In the present study we examined differences in quantitative expression for 35 genes between hybrids and their parents and compared these differences in a heterotic and a non-heterotic hybrid at different developmental stages. The heterotic hybrid had a significant number of genes expressed over the quantity of the better parent at three developmental stages. The non- heterotic hybrid had a minor number of genes expressed over the better parent at the first and the second stage. In addition, the non-heterotic hybrid had a significant number of genes ex- pressed below the level of the worst parent. These results support the significance of regulatory mechanisms involved in the quantitative modulation of gene expression. Since DNA methylation could be considered as a genome-wide general regulatory mechanism that affects the expression of many genes important for the manifestation of heterosis, we measured total DNA methylation in maize parental inbreds and their hybrids using HPLC chromatography, and site-specific DNA methylation changes re-lated to stress using the CRED-RA technique. We found developmental differences in the level of total DNA methylation among the different genotypes, which could be related to hybrid vigor. Stressful growth con-ditions resulted in more methylated DNA (less expressed) and, in general, Corresponding Author : Athanasios S. Tsaftaris, Department of Genetics and Plant Breeding, Aristotelian University of Thessaloniki, 54006 Thessaloniki, Greece
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190 GENETIKA, Vol. 32, No. 3, 189-201, 2000. vigorous hybrids were more resistant to such density induced methylation changes. Key words: gene expression, heterosis, maize, methylation INTRODUCTION Heterosis is a genetic phenomenon, in which hybrids manifest superiority over the inbred parental genotypes, for several quantitative characters, including yield. While plant breeders and agronomists achieved an impressive increase in yield of maize, utilizing heterosis, the biological basis of the phenomenon remains unknown. Previous attempts to understand physiological and biochemical aspects of heterosis demonstrated that maize hybrids possess physiological and biochemical properties superior than those of the parental lines (for review see Tsaftaris 1995).
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