DIFFERENTIAL EXPRESSION OF PHOTOSYNTHESIS GENES IN LEAF TISSUE LAYERSOF PEPEROMIA AS REVEALED BY TISSUE PRINTING

Peperomia has species that may be C-3, show Crassulacean acid metaboli sm (CAM), or CAM-cycling. Species that show CAM progress from C-3 to C AM through CAM-cycling during leaf development. In CAM and CAM-cycling species, CAM metabolism is predominately in the upper multiple epider mis and lower spongy mesophyll, whereas C-3 metabolism is localized mo stly in the palisade mesophyll. Using specific protein and cDNA probes prepared from P-enolpyruvate carboxylase (PEPc) and ribulose-1,5-bisp hosphate carboxylase (Rubisco), we have now studied the differential d istribution of photosynthetic metabolism in Peperomia leaves using the technique of tissue printing. The tissue printing studies detected Ru bisco protein in leaves of C-3 P. orba, but not PEPc. Young C-3 leaves of P. scandens and P. camptotricha showed Rubisco protein, but not PE Pc; however, the mature leaves of these two species that have CAM show ed PEPc protein and RNAs in both the multiple epidermis and spongy mes ophyll. In contrast, Rubisco protein and RNAs were present throughout the leaf. The tissue printing data are consistent with our previously published data showing the differential distribution of photosynthetic metabolism in leaves of Peperomia. Although the tissue printing techn ique is qualitative, coupled with quantitative data it has proven usef ul for the study of function related to structure.