Preferential loss of chloroplast proteins in nitrogen deficient euglena

Two dimensional gel electrophoresis was used to follow changes in the relative amounts of over 500 cellular proteins during nitrogen deficiency and in light limited nitrogen sufficient stationary phase Euglena cultures. Of 53 polypeptides whose relative amount decreased in nitrogen deficient cells, 37 were chloroplast proteins and only 11 were mitochondrial proteins. This corresponds to a decrease in the relative amounts of 77% of the chloroplast proteins and 31% of the mitochondrial proteins found on the two dimensional gel map. Over a similar time period, the relative amounts of only 1 chloroplast and 1 mitochondrial protein decreased in light limited nitrogen sufficient stationary phase cultures. Many of the chloroplast proteins whose level declined during nitrogen deficiency were proteins whose light induced accumulation is independent of chlorophyll synthesis, photosynthetic CO2 fixation and the developmental status of the chloroplast. Taken together, these results indicate that nitrogen deficiency triggers a preferential loss of chloroplast proteins which can not simply be explained through a dependence of protein stability on chlorophyll levels or the developmental status of the chloroplast. © 1988 The Japanese Society of Plant Physiologists (JSPP)