The role of nitrate reduction for anaerobic metabolism of roots
Project management at the University of Würzburg:
Roots frequently experience oxygen deficiency. Nitrate fertilization appears to
facilitate survival of such anoxic or hypoxic phases, but the mechanisms behind
are not understood. We compared the response to anoxia
in roots of two tobacco lines: The WT plants had normal nitrate reductase
activities in roots and leaves. A transformant (obtained by Prof. R. Mendel,
TU Braunschweig) had almost normal nitrate reductase activity in leaves, but
absolutely no activity in the roots.
Under anoxia, roots of the transformant, but not those of the WT, produced
large amounts of alcohol and lactic acid. Due to that, transformant roots had a stronger
cytosolic acidification than those of the WT. Also, the transformants
showed heavy wilting symptoms after a few hours of anoxia, whereas the WT
did not. Similar observations were made when WT plants were fed with tungstate,
which leads to a non-functional nitrate reductase. Thus it is obvious that nitrate
reduction avoids toxic accumulation of fermentation products under anoxia.
In a follow-up project we are presently studying the signal chain that
connects nitrate reduction and fermentation.
Projekt period: from 01.2001 to 06.2002
DFG ,Granting date: 13.07.2000