PLANT PHYSIOLOGY , Vol 115, Issue 2 705-715, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Transgenic Tobacco Plants Expressing Pea Chloroplast Nmdh cDNA in Sense and Antisense Orientation (Effects on NADP-Malate Dehydrogenase Level, Stability of Transformants, and Plant Growth)
M. Faske, J. E. Backhausen, M. Sendker, M. Singer-Bayrle, R. Scheibe and A. von Schaewen
Pflanzenphysiologie, FB 5, Biologie/Chemie, Universitat Osnabruck, D-49069 Osnabruck, Germany
A full-length cDNA encoding light-activated chloroplast NADP-malate
dehydrogenase (NADP-MDH) (EC 1.1.1.82) from pea (Pisum sativum L.) was
introduced in the sense and antisense orientation into tobacco (Nicotiana
tabacum L.). Transgenic plants with decreased or increased expression
levels were obtained. Because of substantial age-dependent differences in
individual leaves of a single plant, standardization of NADP-MDH levels was
required first. Then, extent and stability of over- or under-expression of
Nmdh, the gene encoding NADP-MDH, was characterized in the various
transformants. Frequently, cosuppression effects were observed, indicating
sufficient homology between the endogenous tobacco and the heterologous pea
gene. Analysis of the T1 and T2 progeny of a series of independent
transgenic lines revealed that NADP-MDH capacity ranged between 10% and
[greater than or equal to]10-fold compared with the wild type. Under
ambient conditions whole-plant development, growth period, and fertility
were unaffected by NADP-MDH reduction to 20% of the wild-type level; below
this threshold plant growth was retarded. A positive growth effect was
registered in young plants with stably enhanced NADP-MDH levels within a
defined developmental window.