CORRELATION BETWEEN PVY-RNA AND BNYW-RNA BIOSYNTHESIS AND RIBONUCLEASES ACTIVITIES IN TOBACCO AND SUGAR BEET PLANTS
M SINDELAROVA1, L BURKETOVA1, V TABORSKY2 and L SINDELAR1
1lnstitute of Experimental Botany, Academy of Sciences of the Czech Republic, 160 00 Praha 6, CR; 2Czech Agriculture University, 160 00 Praha 6, CR
Background and objectives
Results and conclusions
Changes in the content and in the subcellular localization of ribonuclease isozymes were determined in mesophyll protoplasts prepared from Nicotiana tabacum cv. Samsun from healthy and PVY-infected plants. Intact chloroplasts, mitochondria and soluble cytosolic proteins were obtained after protoplast disruption by means of differential centrifugation. The 1000 g pellet from healthy protoplasts contained 6.7% , the 15,000 g pellet 13.2%, and the 15,000 g supernatant 83.4% of the total activity of ribonucleases. The 1000 g pellet from infected protoplasts contained 9.9% , the 15,000 g pellet 10.1% and the 15,000 g supernatant 91.0% of the total activity of ribonucleases. In infected protoplasts, activities of these enzymes were enhanced in ruptured protoplasts preparation to 136.9%, in 1000 g pellet to 203%, in 15,000 g pellet to 104%, and in 15,000 g supernatant to 149.5% of healthy mock-inoculated protoplasts. From the results we conclude that in infected tissue of intact plants, the increased activities of these enzymes are due to the increased content of cytosolic (include vacuolar) and chloroplast isozymes.
A linear correlation was found between the content of PVY and tobacco host resistance as well as between the content of BNYVV and the resistance of sugar beet plants to virus multiplication, determined by enhanced levels of ribonucleases involved in viral RNA biosynthesis in susceptible, tolerant and resistant plants. This finding enabled us to quantitatively define the degree of resistance to virus multiplication for use in gene manipulation and breeding. We presuppose the common validity of these relations so that they could be used for the study of virus resistance of further host plants.