The expression of yeast genes under stressed conditions should be understood as a series of steps (mRNA flux) that include the processing, transport, translation, and degradation of mRNA, as well as transcriptional regulation. Recent studies demonstrated the unique phenomena of mRNA flux under ethanol stress conditions or during brewing. Under severe ethanol stress conditions, the transport of non-essential mRNAs from the nucleus to the cytoplasm is suppressed whereas limited kinds of mRNAs are preferentially transported in yeast cells. Not all mRNAs are translated following their cytoplasmic transport; the expression of some mRNAs is regulated by processes such as translational repression or degradation in the cytoplasm, and is dependent on the conditions present. Under severe ethanol stress conditions, cytoplasmic mRNP granules such as processing bodies and stress granules are formed with untranslated mRNAs and various proteins including mRNA-degrading enzymes or translation factors. The author and his colleagues recently found that EXP7 and VEP mRNAs can be preferentially translated in the presence of high-concentration ethanol and vanillin, respectively. They also found that EXP7 and VAP promoters are stress-inducible and enables effective protein synthesis even under severe stress conditions. These promoters may be useful for the improvement of stress-tolerance and biofuel production efficiency via modification of yeast gene expression in the presence of high concentrations of ethanol or vanillin.

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C1 compounds, such as methane and methanol, which have no carbon-carbon bond, are ubiquitous in nature and also emitted from anthropogenic environments. C1-microorganisms (methylotrophs), which can utilize C1-compounds as the sole source of carbon and energy, inhabit various environments and are responsible for carbon circulation of two major greenhouse gases, methane and CO2, called “methane cycle”. Recently, methane and methanol have been reported to be emitted from plants, and the phyllosphere, defined as the aerial part of plants, has been recognized as a habitat for C1-microorganisms. Phyllsophere is thought to be exposed to various kinds of environmental stresses, such as low nutrients, temperature, draught, UV, and so on. In this review, we introduce recent studies on how C1-microbes adapt to and survive on stressful environments.

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Thermococcus kodakarensis is a hyperthermophilic archaeon that thrives over a wide range of moderately high (60°C) to extremely high (100°C) temperatures. By contrast, the closely related genera, Pyrococcus spp., thrives at higher temperatures (70°C to 100°C). Factors such as the expression of the cold inducible DEAD-box RNA helicase, the cold-inducible chaperonin CpkA, and membrane components etc were thought to be involved in the ability of this organism to adapt to cooler environments in T. kodakarensis. In DEAD box RNA helicase, five-adenosine (AAAAA) sequence is located in the region between the SD region and the initiation codon (ATG) is involved in cold induction. A5 -dependent cold-induced expression is related to premature termination. At 85°C and 93°C, clustered A5 might function as transcriptional terminator at sites where an RNA-DNA hybrid would have inherently weak base-pairing. At 60°C, however, the RNA-DNA hybrid might be stabilized and inhibit the release of mRNA from template DNA. Similar A rich sequences have been observed in other cold inducible genes between the SD region and the initiation codon. For cell survival at cold stressed environment, CpkA plays a central role. A cpkA deletant strain showed a poor cell growth at 60°C, but no significant growth defect at 85°C and 93°C. The CpkA variant, in which Glu530 was replaced with Gly (CpkA-E530G), showed increased ATPase activity, with greatest activity at 50°C. The mutant strain, DA4 (pyrF, cpkA-E530G), grew as well at 60°C as the parental KU216 strain. By contrast, DA4 grew more vigorously than parental strain at 50°C. These results suggested that the CpkA-E530G mutation prevented cold denaturation of proteins under cold-stress conditions, thereby enabling cells to grow in cooler environments. It is likely that hyperthermophiles have evolved by obtaining mutation in chaperonin so that they adapt to a colder environment.

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Environmental stresses, such as drought, cold and heat, have negative effects on plant growth. Plants have evolved to obtain sophisticated systems to respond and adapt to environmental stresses. Many plant genes with various functions are induced in response to environmental stresses, and their gene products function in stress tolerance. Plant hormone abscisic acid (ABA) plays important roles in environmental stress responses and adaptation. ABA is important for stomata closure and induction of stress genes under abiotic stress conditions. In environmental stress responses of plants, we have shown the existence of both ABA-dependent and ABA-independent regulatory systems in stressresponsive gene expression, and crosstalk in responses to drought, cold, heat and high salinity. Recently, regulatory systems in ABA responses including biosynthesis, metabolism, signal transduction, and transport have been extensively analyzed to identify key regulators in these processes. Moreover, many stress-inducible genes are used for the improvement of stress tolerance by overexpression. These genes are useful for molecular breeding of drought tolerance in transgenic crops and vegetables.

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Higher plants are sessile organisms. Therefore, even if environments surrounding plants were changed to unfavorite condition, plants are not able to move to optimal place. Thereby, plants have defense system against multiple environmental stresses. Abscisic acid (ABA) is one of plant hormones, which are distributed across higher plant species and is known as a key small molecule for drought stress tolerance and induction of seed dormancy. Both ABA-deficient and -insensitive mutants show wilty phenotype, whereas ABA-over-accumulation and -hypersensitive mutants have drought stress tolerance. Additionally, when ABA action is drastically reduced during seed maturation, seeds germinate on mother plants. Although it appears that early germination is good trait for plant, seeds must keep dormancy under unfavorite condition until optimal environment comes for plant growth. Thus, ABA is thought to be an indispensable molecule for successful prosperity of plants in land. Here, this review describes current ABA metabolic regulation and signal transduction controlling ABA action and introduces applied research examples toward agriculture

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