Expression of two nblA-homologous genes is required for phycobilisome degradation in nitrogen-starved Synechocystis sp PCC6803

One of the responses exhibited by cyanobacteria when they are limited for a n essential nutrient is the rapid degradation of their light-harvesting com plex, the phycobilisome. Phycobilisome degradation is an ordered proteolyti c process. visible by a color change of the cyanobacterial cell from blue-g reen to yellow-green (chlorosis). The small polypeptide NblA plays a key ro le in degradation of phycobilisomes in Synechococcus sp. PCC7942. Unlike Sy nechococcus. Synechocystis sp. PCC6803 has two nblA-homologous genes, nblA1 and nblA2, which are contiguous on the genome. Here we show that nblA1 and nblA2 are simultaneously expressed in Synechocystis 6803 upon nitrogen dep rivation. and are both required for phycobilisome degradation. (C) 2001 Fed eration of European Microbiological Societies. Published by Elsevier Scienc e B.V. All rights reserved.