Annals of Botany 92: 327-328, 2003
© 2003 Annals of Botany Company
Li, P.H. and Palva, E.T. (eds) Plant cold hardiness. Gene regulation and genetic engineering
Plant cold hardiness. Gene regulation and genetic engineering.
Li PH, Palva ET, eds. 2002.
Dordrecht: Kluwer/Plenum.
The International Plant Cold Hardiness Seminar (IPCHS) is held every 5 years, and the sixth IPCHS took place in Helsinki, Finland, in July 2001. From the presentations, 20 excellent papers were selected for inclusion in this book, which is divided into three sections: part 1 is on gene regulation and signal transduction (five papers), part 2 on physiological aspects of plant cold hardiness (11 papers) and part 3 deals with genetic engineering (four papers). Graduate students and researchers who want to catch up on current knowledge in this field will find this book useful.
In part 1, Zhu and colleagues review the types of genes that are switched on/off by exposure to low temperature, and how plants sense low temperature and transduce its signal. Recent work has revealed that a cold-responsive cis-element (DRE/C-repeat) and the trans-acting factors (DREBs/CBFs) that recognize the cis-element play important roles in low temperature signalling, and that constitutive expression of the DREB/CBF-encoding genes confers freezing tolerance to the host plants. Several Arabidopsis thaliana mutants with altered cold responses are reviewed by Zhu et al. and Warren et al. Xin describes how the eskimo1 mutant of arabidopsis, which is more tolerant to freezing, accumulates more free proline and soluble sugars but does not induce cor (cold responsive) genes upon exposure to low temperature. Analysis of these mutants suggests that there are multiple pathways/factors involved in cold signalling and freezing tolerance. Early events triggered by low temperature stress are summarized by Dhindsa et al.: low temperature induces membrane rigidification, cytoskeleton rearrangements and opening of calcium channels. The stimulated calcium flux into the cytoplasm activates a calcium-dependent protein kinase and a MAP kinase cascade, and eventually cold-induced genes are expressed. A role for AtPP2CA, a serine/threonine protein phosphatase, in the cold-signalling pathway is demonstrated by Taehtiharju et al. In their model, AtPP2CA is a negative regulator of the cold-induced, ABA-dependent signalling pathway.
The second section gives an overview of the physiological basis of hardening and dehardening processes in herbaceous and woody plants. Junttila et al. studied environmental regulation of cold hardening in trees, investigating whether daylength and temperature affect the process. At present, studies of trees at the molecular and genetic level are hampered by limited information and a lack of characterized mutants. Arona summarizes cold acclimation in rhododendron. There are over 800 species of rhododendron distributed throughout the Northern hemisphere, ranging from tropical to polar climates, and varying widely in their tolerance to freezing. A 25 kDa dehydrin seems to be a useful genetic marker to estimate the potential for freeze tolerance in this species. Fennell and Mathiason have used nuclear magnetic resonance imaging to collect anatomical and biophysical information to determine differential tissue responses in the cold acclimation process, analysing the early cold-acclimation response in grapes. Cryopreservation is becoming a very important tool for long-term storage of plant genetic resources. Sakai et al. have developed a potential cryogenic protocol using vitrification, and have successfully applied it to more than 30 temperate and tropical plants. Cattivelli et al. report the expression of cold-regulated genes in barley. They also used an albino mutant and characterized the cold-responsive signal transduction pathways in barley. The group further extended the work in the field to identify major loci affecting freezing tolerance in barley. Glutathione and carbohydrate biosynthesis in cold acclimation of wheat was studied by Galiba et al. using chromosome-substitution, -recombinant and -deletion lines. They reveal that the 5A chromosome of wheat carries a gene cluster responsible for the freezing response. Photosynthesis at low temperature was studied by Hurry’s group: cold-acclimated arabidopsis leaves recovered net CO2 assimilation and changed the carbon pathway to stimulate sucrose synthesis. The authors also showed that short-term exposure to low temperature leads to a rapid and acute Pi limitation in photosynthesis metabolism. Kawamura and Uemura examined changes in the plasma membrane of cold-acclimated arabidopsis leaves, analysing amounts of lipids and proteins. Using 2D-PAGE and MALDI-TOF mass spectrometry, seven membrane proteins were found to increase during cold acclimation, including a RAD23 homologue, two dehydrins and carbonic anhydrase. A cryoprotective protein (cryoprotectin) from leaves of cold-acclimated savoy cabbage has been purified by Schilling et al. The protein, which belongs to a family of lipid transfer proteins (LTPs), protects thylakoids. Some proteins in the LTP family have cryoprotective activity, but others do not. Wisniewski et al. have investigated extrinsic ice nucleation in plants, addressing the effect of ice-nucleation-active bacteria, hydrophobic barriers and an antifreeze protein of insect origin. It is known that ABA treatment mimics the cold-acclimated status in plants. Chen and Li indicate that this phytohormone reduces Ca2+ overload, attenuates the production of reactive oxygen species during chilling, and induces cyanide- resistant alternative oxidase activity.
In the last part, transgenic approaches to enhance chilling/freezing tolerance are discussed. Genes for Mn-SOD, dehydrin and CBF1 and another stress-associated protein have been introduced into canola, potato or flax by Gusta et al., and the frost-, heat- and drought-tolerance of the transgenics tested. Palva and colleagues have engineered trehalose biosynthesis to improve stress tolerance in arabidopsis and show that the transgenics are tolerant to freezing and drought stresses. Yuwansiri et al. summarize the success of transgenic plants with regards to cold tolerance and introduce work showing that transgenic plants have high glycinebetaine contents. Saruyama’s group has made transgenic rice with the wheat catalase gene. The transgenic rice showed improved tolerance to cold.
There are numerous books and review articles describing cold-responsive genes and cold signalling on molecular biological and genetic bases, but it is difficult to find books covering all aspects of cold hardiness in plants. In this sense this book is commendable. Of course, one must remember that this is a rapidly advancing field. For this reason, the next ICPHS will be held 3, not 5, years after the last, in Sapporo, Japan, in 2004.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||