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Plant Physiol, January 2002, Vol. 128, pp. 73-83
Altered Levels of Proline Dehydrogenase Cause
Hypersensitivity to Proline and Its Analogs in
Arabidopsis1
Srikrishnan
Mani,
Brigitte
Van de Cotte,
Marc
Van Montagu, and
Nathalie
Verbruggen2*
Vakgroep Moleculaire Genetica, Departement Plantengenetica, Vlaams
Interuniversitair Instituut voor Biotechnologie, Universiteit Gent,
K.L. Ledeganckstraat 35, B-9000 Gent, Belgium
Pro dehydrogenase (PDH) catalyzes the first and rate-limiting step
in the Pro catabolic pathway. In Arabidopsis, this enzyme is encoded by
At-PDH. To investigate the role of Pro catabolism in
plants, we generated transgenic Arabidopsis plants with altered levels
of PDH by sense (PDH-S plants) and antisense (PDH-AS plants) strategies. Free Pro levels were reduced by up to 50% in PDH-S plants
under stress and recovery conditions and enhanced by a maximum of 25%
in PDH-AS plants, despite large modifications of the
At-PDH transcript and At-PDH protein levels. A similar
trend in free Pro levels was observed in the PDH-S and PDH-AS seeds without visible effects on germination or growth. Under stress conditions, PDH transgenic plants showed no signs of change in osmotolerance. However, addition of exogenous Pro increased survival rates of salt-stressed PDH-S plants by 30%. Isotope-labeling studies showed that the conversion of [14C]Pro to Glu was reduced
in PDH-AS plants and increased in PDH-S plants, especially under stress
conditions. Furthermore, PDH-AS plants were hypersensitive to exogenous
Pro, whereas PDH-S plants were sensitive to Pro analogs. These findings
demonstrate that altered At-PDH levels lead to weakly modified free Pro
accumulation with a limited impact on plant development and growth,
suggesting a tight control of Pro homeostasis and/or gene redundancy.
1
This work was supported by the European Union
Training and Mobility (grant no. FMRX-CT96-0007). S.M. is indebted to
the "Bijzondere Onderzoekfonds" of the Ghent University for a
predoctoral fellowship (011NEU199).
2
Present address: Laboratoire de Physiologie et de
Génétique Moléculaire des Plantes, Université
Libre de Bruxelles, CP 242, Boulevard du Triomphe, B-1050 Brussels, Belgium.
*
Corresponding author; e-mail nverbru{at}ulb.ac.be; fax
32-2-650-5421.
© 2002 American Society of Plant Physiologists
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