Response of nitrogenase to altered carbon supply in a Frankia-Alnus incana symbiosis
Lundquist, P; Huss-Danell, K
To study the effect of altered carbon supply on nitrogenase (EC 188.8.131.52), plants of Alnus incana (L.) Moench in symbiosis with the local source of Frankia were exposed to darkness for 2 days, and then returned to normal light/dark conditions. During the dark period nitrogenase activity in vivo (intact plants) and in vitro (Frankia cells supplied with ATP and reductant), measured as acetylene reduction activity, was almost completely lost. Western blots for both the Fe-protein (dinitrogenase reductase) and the MoFe-protein (dinitrogenase) showed that, in particular, the amount of MoFe-protein was strongly reduced during darkness. Protein stained sodium dodecyl sulphate-polyacrylamide gels of Frankia protein showed that the nitrogenase proteins were the only abundant proteins that clearly decreased during darkness. During recovery, studied for 4 days, nitrogenase activity in vivo recovered to the level before dark treatment but was still only half of control activity, Nitrogenase activity in vitro and the amount of MoFe-protein, both expressed per Frankia protein, recovered and reached similar values in previously dark treated plants and in control plants. The rate of recovery was similar to the increase in activity of control plants, suggesting growth of Frankia in addition to synthesis of nitrogenase proteins during the recovery after carbon starvation.
Ultrastructure; Alnus incana; carbon starvation; darkness; Fe-protein; Frankia; grey alder; MoFe-protein; nitrogenase; recovery of nitrogenase activity; symbiosis
1991, Volume: 83, number: 3, pages: 331-338
Publisher: Blackwell Publishing Ltd
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