Accumulation of plastocyanin mRNA lacking 5 ' region in the green alga Pediastrum boryanum grown under copper-deficient conditions

In the green alga Pediastrum boryanum NIES-301, plastocyanin accumulates un der copper-sufficient conditions and cytochrome c(6) accumulates under copp er-deficient conditions. We cloned the cDNA which encodes pre-apoplastocyan in from P. boryanum cultured under the copper-sufficient condition. The ded uced amino acid sequence of the pre-apoplastocyanin protein consists of 151 amino acid residues including a putative bipartite presequence of 53 amino acid residues. Southern blot analysis of P. boryanum genomic DNA indicated that pre-apoplastocyanin is encoded by a single nuclear gene. Northern blo t analysis showed that copper-deficient cells accumulated a shorter form of the mRNA of pre-apoplastocyanin, which did not generate pre-apoplastocyani n in the wheat-germ translation system. The difference in size was ascribed to the absence of the 5' region in the mRNA of pre-apoplastocyanin obtaine d from the copper-deficient cells, which accounts for the absence of plasto cyanin under these conditions. This phenomenon represents a novel regulator y mechanism, although details of the mechanism are not yet known.