Abstract
Excretion of organic acids, especially citrate, from roots is a tolerance mechanism to aluminum (Al) stress. The mechanism is suggested to be controlled by citrate metabolism and transport system on plasma membrane. A key enzyme in the metabolism is NADP-isocitrate dehydrogenase (NADP-ICDH), which is a member of citrate conversion pathway. We generated transgenic Eucalyptus, in which NADP-ICDH was down-regulated by RNA interference procedure. Two transgenic lines showing 50% and 20% of NADP-ICDH activity of wild-type plants were not changed activity of other enzymes. Citrate concentration in roots of the transgenic lines was 1.4-1.6 times higher than that of wild-type plants. In addition, transgenic lines excreted citrate 1.5-1.7 times more. Growth of transgenic line on an acid soil was greater than that of wild-type plant. We inferred that RNAi-mediated repression of NADP-ICDH is a useful technology to confer Al tolerance to woody plants.
