Heat shock Hsp70 protein is chloroplast-encoded in the chromophytic alga Pavlova lutherii

Abstract

Heat shock proteins are ubiquitous and highly conserved. Recently they have become implicated in the import of proteins into organelles. All the heat shock genes characterized to date, however, are known or assumed to be encoded in the nuclear genome even if the corresponding protein can be localised in the mitochondrion or chloroplast. In contrast, we identify here an hsp70 gene in the unicellular chromophytic alga Pavlova lutherii which is located on the chloroplast genome. Localisation of this gene to the chloroplast chromosome is confirmed by Southern blot analysis and pulse-field gel electrophoresis which also reveals that the length of the P. lutherii chloroplast chromosome is 115 kb. We compare the predicted protein of this hsp70 gene with that of maize and of the analogous proteins in the prokaryotic organisms Escherichia coli and Synechocystis PCC6803. The greatest identity is found with the cyanobacterium Synechocystis PCC6803.

Plastid genome size and heterogeneous base composition of nuclear DNA from Ochrosphaera neapolitana (Prymnesiophyta)

“…Our PFGE results reveal a plastid genome size in O. neapolitana of approximately 165 kb and confirm the size reported for P. lutheri (c. 120 kb vs 115 kb determined by Scaramuzzi et al 1992). Thus, O. neapolitana has a significantly larger plastid genome than other chlorophyll a + c-containing algae.…”

“…Pavlova lutheri was included in our experiments because it represents a closely related evolutionary lineage within the Prymnesiophyta (Edvardsen et al 2000) and because its plastid genome size (115 kb, i.e. well within the normal range) has been previously reported using PFGE as well (Scaramuzzi et al 1992). The three probes revealed DNA bands of approximately 165 kb for O. neapolitana (Fig.…”

Characteristics of an Hsp70 Homolog Localized in Higher Plant Chloroplasts That Is Similar to DnaK, the Hsp70 of Prokaryotes

“…cDNAs have been cloned from higher plants that encode Hsp70 homologs localized to the chloroplast envelope (Ko et al, 1992) and stroma (Marshall and Keegstra, 1992). In some eukaryotic algae, Hsp70 is encoded on the chloroplast genome (Reith and Munholland 1991;Scaramuzzi et al, 1992). We identified Hsp70 in chloroplasts from Euglena gracilis, maize, and spinach based on its similarity to DnaK.…”

Characterisation of a chloroplast‐encoded sec Y homologue and atpH from a chromophytic alga Evidence for a novel chloroplast genome organisation

“…haherii was cultivated in Provosoli's enrichment media [12]. Harvesting, pr0paration of chloroplast DNA, construction of clone banks and hybridisation techniques have been previously described [4]. Manipulations of DNA were performed according to standard protocols [13] or, when using DNA-modifying en2ymes, to the manufacturers instructions.…”

“…There are indications, based on nucleotide sequence data for the Rubisco genes, rbcL and rbcS, that the chromophytic alga contain several genes that are similar to prokaryotic genes but which are not present in higher plant and green algal chloroplast DNA [3]. Some genes involved in protein translocation have also been retained on the chloroplast genome of eukaryotic algae outside of the chlorophyta [4][5][6]. The sec Y gone is found in both Escherichia cell [7] and Bacillus subtilis [8] where it forms part of the spc operon of the ribosomal protein (rp) gone cluster and in Cyanophora paradoxa [9] where it is located immediately adjacent to the final gone of this operon.…”