FAIR-CT96-5055 The effects of differential compartmentation of the antioxidant defence system on the sensitivity of the bundle sheath and mesophyll cells of maize to low temperature

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Objectives:

The aim of this work was to analyse the distribution of glutathione reductasc (GR) between bundle sheath and mesophyll cells of maize leaves from plants grown at optimal and sub-optimal temperatures.

Activities and Results:

Glutathione reductase was assayed in bundle sheath (BS) and mesophyll (M) cells of maize from plants grown at 20, 18 and 15 degrees C. The purity of each fraction was determined by measuring the compartment-specific marker enzymes, ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase, respectively. GR activity and the abundance of GR protein and mRNA increased in plants growing at 15 and 18 degrees C compared to those grown at 20 degrees C. In all cases GR activity was found only in the mesophyll fractions of the leaves with no GR activity detectable in the bundle sheath extracts. Immunogold labelling with antibodies specific to GR showed that GR protein was exclusively localised in the mesophyll cells of leaves at all growth temperatures, whereas GR transcripts determined by in situ hybridisation techniques were observed in both cell types at equal abundance.

Conclusions:

These results indicate that post-transcriptional regulation prevents GR accumulation in the BS cells of maize leaves. The limitation on the capacity for regeneration of GSH in this compartment that this engenders may contribute to the extreme chilling sensitivity of maize leaves.

Keywords: Cold tolerance, glutathione reductase, maize.

Contacts

Scientific Supervisor

• Christine FOYER / Institute of Grassland & Environmental Research Department of Environmental Biology / UNITED KINGDOM