Inducible expression of plasma membrane H+-ATPase in the roots of figleaf gourd plants under chilling root temperature

Figleaf gourd plants were grown under different root temperatures and the acclimation process of the roots was investigated. Conditioning of the roots by a gradual decrease (2 degrees C h(-1)) in root temperature to 6 degrees C considerably lowered the electrolyte leakage of the plant leaves compared to non-conditioned roots. A root temperature of 6 degrees C was critical for the increase in H+-ATPase (EC 3.6.1.35) activity in the plasma membranes of the roots and this increase was abolished by the addition of cycloheximide in the root medium. The H+-transport rate of the plasma membranes was also increased by low root temperature. Increases in the amount of the plasma membrane H+-ATPase gene transcription and translation in the plant roots under chilling root temperature were demonstrated by Northern and Western blot analysis, respectively. A correlation between the leaf temperature, measured by an infra-red thermometer, and the H+-ATPase activity suggests the involvement of H+- ATPase in the root acclimation process.