Plant Physiol, March 2000, Vol. 122, pp. 667-676
Post-Transcriptional Regulation Prevents Accumulation of
Glutathione Reductase Protein and Activity in the Bundle Sheath
Cells of Maize1
Gabriela M.
Pastori,*
Philip M.
Mullineaux, and
Christine H.
Foyer
Biochemistry and Physiology Department, IACR-Rothamsted, Harpenden,
Herts AL5 2JQ, United Kingdom (G.M.P., C.H.F.); and Department of
Applied Genetics, John Innes Centre, Colney, Norwich NR4 7UH,
United Kingdom (P.M.M.)
Glutathione reductase (GR; EC
1.6.4.2) activity was assayed in bundle sheath and mesophyll cells of
maize (Zea mays L. var H99) from plants grown at 20°C,
18°C, and 15°C. The purity of each fraction was determined by
measuring the associated activity of the compartment-specific marker
enzymes, Rubisco and phosphoenolpyruvate carboxylase,
respectively. GR activity and the abundance of GR protein and mRNA
increased in plants grown at 15°C and 18°C compared with those
grown at 20°C. In all cases GR activity was found only in mesophyll
fractions of the leaves, with no GR activity being detectable in bundle
sheath extracts. Immunogold labeling with GR-specific antibodies showed
that the GR protein was exclusively localized in the mesophyll cells of
leaves at all growth temperatures, whereas GR transcripts (as
determined by in situ hybridization techniques) were observed in both
cell types. These results indicate that post-transcriptional regulation
prevents GR accumulation in the bundle sheath cells of maize leaves.
The resulting limitation on the capacity for regeneration of reduced
glutathione in this compartment may contribute to the extreme chilling
sensitivity of maize leaves.
1
This work was funded by the European Commission
(AIR1-CT92-0205, Engineering Stress Tolerance in Maize) and by an
European Economic Community Research Training Fellowship (FAIR
CT-965055 to G.P.).
*
Corresponding author; e-mail gabriela.pastori{at}bbsrc.ac.uk; fax
44-1582-763010.
© 2000 American Society of Plant Physiologists
