Salinity-stress-induced proteins in two nitrogen-fixing Anabaena strains differentially tolerant to salt

Abstract

Salinity altered the protein synthesis patterns in two cyanobacterial strains: Anabaena torulosa, a salt-tolerant brackish water strain, and Anabaena sp. strain L-31, a salt-sensitive freshwater strain. The cyanobacterial response to salinity was very rapid, varied with time, and was found to be correlated with the external salt (NaCl) concentration during stress. Salinity induced three prominent types of modification. First, the synthesis of several proteins was inhibited, especially in the salt-sensitive strain; second, the synthesis of certain proteins was significantly enhanced; and third, synthesis of a specific set of proteins was induced de novo by salinity stress. Proteins which were selectively synthesized or induced de novo during salt stress, tentatively called the salt-stress proteins, were confined to an isoelectric pI range of 5.8 to 7.5 and were distributed in a molecular mass range of 12 to 155 kilodaltons. These salt-stress proteins were unique to each Anabaena strain, and their expression was apparently regulated coordinately during exposure to salt stress. In Anabaena sp. strain L-31, most of the salt-stress-induced proteins were transient in nature and were located mainly in the cytoplasm. In A. torulosa, salt-stress-induced proteins were evenly distributed in the membrane and cytoplasmic fractions and were persistent, being synthesized at high rates throughout the period of salinity stress. These initial studies reveal that salinity-induced modification of protein synthesis, as has been demonstrated in higher plant species, also occurs in cyanobacteria and that at least some of the proteins preferentially synthesized during salt stress may be important to cyanobacterial osmotic adaptation.

Alterations of protein synthesis in the cyanobacterium Synechocystis sp. PCC 6803 after a salt shock

“…PCC 6803 (Fig. 2B), as was also found in Anabaena by Apte & Bhagwat (1989). This is in good agreement with our quantitative measurements which demonstrated a reduction of total protein synthesis in these cells.…”

“…Whereas the synthesis of proteins 34, 35, 36 was enhanced only during the adaptation phase, that of proteins 21, 32 and 38 was increased especially in saltadapted cells. The occurrence of transient and persistent salt-stress-induced proteins was also found in Anabaena strains (Apte & Bhagwat, 1989). Our relatively long pulse periods (20min) may also have led to labelling of proteins that are only weakly synthesized, so that it is difficult to differentiate between newly induced proteins and proteins synthesized only at an enhanced rate.…”

“…Therefore, changes in the protein composition of cyanobacteria may also be involved in the process of salt adaption. Salt-induced protein synthesis has been demonstrated in Escherichia coli (hop operon; Clark & Parker, 1984), in Bacillus subtilis (Hecker et al, 1988), in two Anabaena strains (Apte & Bhagwat, 1989) and in higher plants (e.g. Hurkman & Tanaka, 1988).…”

A detailed time series assessment of the diet of Lesser Flamingos: further explanation for their itinerant behaviour

“…Vonshak & Tomaselli (2000) have shown that at high salinities, protein levels in Arthrospira decrease while carbohydrates increase as an adaptation for efficient osmoregulation. In addition from the experiments conducted by Apte & Bhagwat (1989) on two Anabaena strains, they observed that exposure to high salinity resulted in inhibition of protein synthesis.…”

Glucosylglycerol accumulation during salt acclimation of two unicellular cyanobacteria

“…Fourthly, altered gene expression leading to modifications in the pattern of protein synthesis and the appearance of stress proteins (Apte & Bhagwat, 1989;Hagemann et al, 1990). Sadka et al (1989) have, however, questioned whether differential gene expression is really involved.…”