Vacuolar proton pumps activities supply power to the vacuolar secondary active transport system in plants. Plant response to salt and water stress have much in common. The salinity reduces the ability of plants to take up water, and this quickly cause reduction in growth rate, along with a suite of metabolic changes identical to those cause by water stress. The ability of plant cells to survive under saline conditions can be summarized as the ability to maintain normal ionic conditions in the cytoplasm. In the present study, we evaluate the expression of the vacuolar proton pumps from Vigna unguiculata (L.) Walp cv. Vita 5 hypocotyls in response to salt and osmotic stress. The seeds of V. unguiculata cv. Vita 5 were germinated in water and after 3 days were transferred to Hoagland's medium and grown in the absence (control), presence of NaCl (0,1 M) or presence of manitol (0,2 M) during 4 and 7 days at green house. Total RNA was isolated from hypocotyls. The mRNA was indirectly quantified by the cDNA obtained through RT-PCR using specific. The RT-PCR analysis showed a rapidly response to osmotic stress increasing approximately 3 times mRNA levels of the V-ATPase subunit A and PPase com pared to control condition after 4 days under stress. However, there were no significant changes between mRNA levels from seedlings under control and stress condition after 4 days in the green house. The PPase mRNA level was approximately 4 times higher than ATPase from 10-day-old seedlings in control condition. ATPase mRNA levels was approximately 4 folds enhanced in both stress condition. Contrarily, PPase mRNA level was similar in control as well as salt stress condition and was half decreased under osmotic stress. Results show a general differential expression of the vacuolar proton pumps, suggesting its fine regulation.
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