Cell-Specific Expression of Rubisco Small Subunit and Rubisco Activase Genes in C₃ and C₄ Species of Atriplex

Abstract

In situ hybridisation techniques have been used to determine the distribution of mRNAs for ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco: EC 4.1.1.39) and Rubisco activase in leaves of Atriplex patula L. (C3) and A. rosea L. (C4). In A. patula, mRNA for Rubisco small subunit (encoded by the rbcS gene family) was found to accumulate in the mesophyll and bundle sheath, while in A. rosea it accumulated in the bundle sheath only, as shown previously for the C₄ monocot Zea mays L. The spatial distribution of rca transcripts for Rubisco activase paralleled that for the rbcS transcripts in both C₃ and C₄ Atriplex species, providing evidence that Rubisco activase is required in cells only where Rubisco is present.