The action in vivo of glycine betaine in enhancement of tolerance of Synechococcus sp. strain PCC 7942 to low temperature

Abstract

The cyanobacterium Synechococcus sp. strain PCC 7942 was transformed with the codA gene for choline oxidase from Arthrobacter globiformis under the control of a constitutive promoter. This transformation allowed the cyanobacterial cells to accumulate glycine betaine at 60 to 80 mM in the cytoplasm. The transformed cells could grow at 20؇C, the temperature at which the growth of control cells was markedly suppressed. Photosynthesis of the transformed cells at 20؇C was more tolerant to light than that of the control cells. This was caused by the enhanced ability of the photosynthetic machinery in the transformed cells to recover from lowtemperature photoinhibition. In darkness, photosynthesis of the transformed cells was more tolerant to low temperature such as 0 to 10؇C than that of the control cells. In parallel with the improvement in the ability of the transformed cells to tolerate low temperature, the lipid phase transition of plasma membranes from the liquid-crystalline state to the gel state shifted toward lower temperatures, although the level of unsaturation of the membrane lipids was unaffected by the transformation. These findings suggest that glycine betaine enhances the tolerance of photosynthesis to low temperature.Various organisms accumulate compatible solutes in their cells under stressful conditions, such as high salt (12,17,26), dehydration (37), and low temperature (15). Among such compatible solutes, glycine betaine (hereafter referred to as betaine) is widely distributed in higher plants (27), animals (7, 16), and bacteria (5). Betaine is a bipolar compound with both positive and negative charges within a single molecule (26). The physiological functions of betaine have not been unequivocally defined, and it has been suggested that betaine protects the cells from salt stress by maintaining osmotic balance with the environment (27) and by stabilizing the quaternary structure of complex proteins (13,18,20,25,30,35). For example, betaine prevents the dissociation of ribulose-1,5-bisphosphate carboxylase-oxygenase (13) and the photosystem II complex (24, 25) under high-salt conditions. However, since betaine is not the only compound that is synthesized in cells under salt or dehydration stress, the possibility remains that betaine might not have a direct effect in the protection of cells against such stresses.To examine whether the effect of betaine in vivo is direct, we established a system for the biosynthesis of betaine in cells of a cyanobacterium, Synechococcus sp. strain PCC 7942, by transformation with the codA gene for choline oxidase from Arthrobacter globiformis, which oxidizes choline to betaine (6). The resultant transformed cells accumulated betaine at an intracellular level of 60 to 80 mM and acquired the ability to tolerate salt stress. Therefore, it appeared that betaine directly protected these cells against salt stress. A similar result was obtained by Nomura et al. (21), such that the transformation of the same cyanobacterial cells with the bet gene operon of Escherichia coli a...

Shewanella pealeana sp. nov., a member of the microbial community associated with the accessory nidamental gland of the squid Loligo pealei

“…The glycine-betaine biosynthesis operon encoding the choline oxidase gene ( c o d ) has been recently cloned and sequenced from a halophile (Canovas et al, 1996). It has been subsequently expressed in other organisms (Deshnium et al, 1997;Hayashi et al, 1997) to enhance tolerance to salt and cold stress. An excellent starting point for future studies would be to determine whether this operon is present in the S .…”

Quantification of glycine betaine, choline and trimethylamine N-oxide in seawater particulates: Minimisation of seawater associated ion suppression

“…For example, TMAO and GBT interact with photosystem I [3]. Increased recovery rates of photosystem II (PSII) have been observed in a cyanobacterium engineered to accumulate glycine betaine in the cytoplasm [4]. TMAO also stabilizes the folded state of proteins [5].…”

Transformation with a gene for choline oxidase enhances the cold tolerance of Arabidopsis during germination and early growth

“…The transformed plants showed significantly elevated tolerance to salt stress. We also transformed Synechococcus with the codA gene, and the transformed cells were tolerant to both salt stress and low-temperature stress (Deshnium et al 1995;Deshnium et al 1997).…”

“…The transformed plants showed significantly elevated tolerance to salt stress. We also transformed Synechococcus with the codA gene, and the transformed cells were tolerant to both salt stress and low-temperature stress (Deshnium et al 1995;Deshnium et al 1997).In the present study, we examined the tolerance of transformed A. thaliana to low-temperature stress, focusing on Plant, Cell and Environment (1998) the imbibition and germination of seeds and the growth of seedlings. Our primary objective was to determine whether synthesis in vivo of betaine confers tolerance to low-temperature stress during the early stages of the plant's life cycle that are critical for the successful establishment of seedlings.…”