Cold stress causes rapid but differential changes in properties of plasma membrane H+-ATPase of camelina and rapeseed

Camelina (Camelina sativa) and rapeseed (Brassica napus) are well-established oil-seed crops with great promise also for biofuels. Both are cold-tolerant, and camelina is regarded to be especially appropriate for production on marginal lands. We examined physiological and biochemical alterations in both species during cold stress treatment for 3 days and subsequent recovery at the temperature of 25 °C for 0, 0.25, 0.5, 1, 2, 6, and 24 h, with particular emphasis on the post-translational regulation of the plasma membrane (PM) H+-ATPase (EC3.6.3.14). The activity and translation of the PM H+-ATPase, as well as 14-3-3 proteins, increased after 3 days of cold stress in both species but recovery under normal conditions proceeded differently. The increase in H+-ATPase activity was the most dramatic in camelina roots after recovery for 2 h at 25 °C, followed by decay to background levels within 24 h. In rapeseed, the change in H+-ATPase activity during the recovery period was less pronounced. Furthermore, H+-pumping increased in both species after 15 min recovery, but to twice the level in camelina roots compared to rapeseed. Protein gel blot analysis with phospho-threonine anti-bodies showed that an increase in phosphorylation levels paralleled the increase in H+-transport rate. Thus our results suggest that cold stress and recovery in camelina and rapeseed are associated with PM H+-fluxes that may be regulated by specific translational and post-translational modifications.