Abstract:The desC gene for the acyl-lipid Delta9-desaturase from the thermophilic cyanobacterium Synechococcus vulcanus was introduced into Nicotiana tabacum under control of the 35S promoter. Expression of the desaturase was confirmed by Western blotting. Lipid analysis revealed that lipid content and the extent of fatty acid unsaturation significantly increased in leaves of transgenic plants. Chilling tolerance of those plants also increased, as estimated by the electrolyte leakage from the tissues damaged by cold tr… Show more
“…and Ca 2? -binding proteins, such as calmodulin, the activation of G-proteins, and the activation of phospholipid signaling, which results in the accumulation of phosphatidic acid (Mittler et al 2004) and activation of polyunsaturated FA peroxidation in membrane lipids (Orlova et al 2003;Maali-Amiri et al 2007). ROS signals can also exert their effects directly through the activation of redox-responsive proteins, such as transcription factors and protein kinases (Hung et al 2005;Chinnusamy et al 2007).…”
Low temperature is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops. Many plants increase in freezing tolerance in response to low temperatures. This phenomenon needs a vast reprogramming of gene expression which results in the adjusted metabolic-structural alterations. However, the efficient adjustments are dependent on proper cold signal transduction. The first stage is cold stress signal perception which is carried out by different pathways. Transcriptional cascades are next players which operate through ABA-dependent and ABA-independent pathways to induce cold-regulated (COR) gene expression and the result is increasing in the levels of hundreds of metabolites, which some of them are known to have protective effects against the damaging effects of cold stress and some like soluble sugars, reactive oxygen species and photosynthetic metabolites are thought to act as signaling molecules and regulate special COR genes. The different aspects of these events are discussed in detail below.
“…and Ca 2? -binding proteins, such as calmodulin, the activation of G-proteins, and the activation of phospholipid signaling, which results in the accumulation of phosphatidic acid (Mittler et al 2004) and activation of polyunsaturated FA peroxidation in membrane lipids (Orlova et al 2003;Maali-Amiri et al 2007). ROS signals can also exert their effects directly through the activation of redox-responsive proteins, such as transcription factors and protein kinases (Hung et al 2005;Chinnusamy et al 2007).…”
Low temperature is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops. Many plants increase in freezing tolerance in response to low temperatures. This phenomenon needs a vast reprogramming of gene expression which results in the adjusted metabolic-structural alterations. However, the efficient adjustments are dependent on proper cold signal transduction. The first stage is cold stress signal perception which is carried out by different pathways. Transcriptional cascades are next players which operate through ABA-dependent and ABA-independent pathways to induce cold-regulated (COR) gene expression and the result is increasing in the levels of hundreds of metabolites, which some of them are known to have protective effects against the damaging effects of cold stress and some like soluble sugars, reactive oxygen species and photosynthetic metabolites are thought to act as signaling molecules and regulate special COR genes. The different aspects of these events are discussed in detail below.
“…Chilling sensitivity was analyzed by measuring the electric conductivity (Orlova et al 2003) of the third to fifth leaves of 45-day-old greenhouse poplar plants. Briefly, leaves were collected and cut into 4 9 4-cm squares.…”
In plant species, the level of polyunsaturated fatty acids (PUFAs) is essential for cold acclimation. To test whether changes in PUFA levels can lead to the alteration of freezing tolerance in poplar trees, we up- and down-regulated a Populus tomentosa Delta-12 fatty acid desaturase gene (PtFAD2) in the hybrid poplar (P. alba x P. glandulosa) clone 84 K. Real-time PCR results demonstrated that compared to untransformed control lines, the transcriptional level of PtFAD2 increased by up to 90% in over-expressing poplar lines (line OE-1) and decreased in down-regulated RNAi lines by up to 64% (line DR-1). As a result, the content of linoleic (C18:2) and linolenic (C18:3) unsaturated fatty acids (FAs) in total FAs increased by 7.5 and 3.9%, respectively, in the OE-1 line and decreased by 14.4 and 5.4% in the DR-2 line when compared to non-transgenic lines. After freezing treatment at -4 degrees C for 3 h without pre-cold acclimation, the survival rates of the PtFAD2-over-expressing cuttings were significantly higher (60% for OE-1) than those of non-transgenic plants (36.7%) and down-regulated lines (10% for DR-2). These results clearly demonstrate that the expression level of PUFAs substantially affected the freezing tolerance of hybrid poplar cuttings and could thus be utilized as an effective strategy to improve poplar anti-freezing traits through genetic engineering biotechnology.
Over the years, cyanobacteria have been regarded as ideal model systems for studying fundamental biochemical processes like oxygenic photosynthesis and carbon and nitrogen assimilation. Additionally, they have been used as human foods, sources for vitamins, proteins, fine chemicals, and bioactive compounds. Aiming to increase plant productivity as well as nutritional values, cyanobacterial genes involved in carbon metabolism, fatty acid biosynthesis, and pigment biosynthesis have been intensively exploited as alternatives to homologous gene sources. In this short review, transgenic plants with cyanobacterial genes generated over the last two decades are examined, and the future prospects for transgenic crops using cyanobacterial genes obtained from functional genomics studies of numerous cyanobacterial genomes information are discussed.
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