Cold Hardening In Wheat Research Articles

Regulation of gene expression by chromosome 5A during cold hardening in wheat

Cold hardening is necessary to achieve the genetically determined maximum freezing tolerance and to reduce yield losses in winter cereals. The aim of the present study was to determine a set of genes with an important role in this process, by comparing of chromosome 5A substitution lines with different levels of freezing tolerance, since chromosome 5A is a major regulator of this trait. During 21 days of treatment at 2 degrees C, 303 genes were up-regulated, while 222 were down-regulated at most sampling points, and 156 at around half of them (out of the 10,297 unigenes studied). The freezing-tolerant substitution line exhibited 1.5 times as many differentially expressed genes than the sensitive one. The transcription of 78 genes (39 up-regulated) proved to be chromosome 5A-dependent. These genes encoded proteins involved in transcriptional regulation, defence processes and carbohydrate metabolism. Three of the chromosome 5A-related genes, coding for a cold-responsive, a Ca-binding and an embryo and meristem-related protein, were genetically mapped and characterized in further detail. The present experimental system was appropriate for the selection of chromosome 5A-related genes involved in short- and long-term cold acclimation in wheat. By modifying the expression of these genes it may be possible to improve freezing tolerance.

Non-Invasive Monitoring of the Light-Induced Cyclic Photosynthetic Electron Flow during Cold Hardening in Wheat Leaves

The effect of irradiance during low temperature hardening was studied in a winter wheat variety. Ten-day-old winter wheat plants were cold-hardened at 5 degrees C for 11 days under light (250 micromol m(-2) S(-1)) or dark (20 micromol m(-2) s(-1)) conditions. The effectiveness of hardening was significantly lower in the dark, in spite of a slight decrease in the Fv/Fm chlorophyll fluorescence induction parameter, indicating the occurrence of photoinhibition during the hardening period in the light. Hardening in the light caused a downshift in the far-red induced AG (afterglow) thermoluminescence band. The faster dark re-reduction of P700+, monitored by 820-nm absorbance, could also be observed in these plants. These results suggest that the induction of cyclic photosynthetic electron flow may also contribute to the advantage of frost hardening under light conditions in wheat plants.

Mapping of Genes Involved in Glutathione, Carbohydrate and COR14b Cold Induced Protein Accumulation during Cold Hardening in Wheat

Using some of the chromosome substitution lines developed from the crosses of the donor Cheyenne to Chinese Spring we showed that the accumulation of water soluble carbohydrates during different stages of hardening was time dependent. More over there was a significant correlation between the rate of carbohydrate accumulation and the frost tolerance. The expression and regulation of a wheat gene homologous to the barley cold regulated corl4b gene was compared in frost sensitive and frost tolerant wheat genotypes at different temperatures. Studies made with chromosome substitution lines showed that the threshold induction temperature polymorphism of the cor14b wheat homologous gene was controlled by loci located on chromosome 5A of wheat, while corl4b gene was mapped, in Triticum monococcum, onto the long arm of chromosome 2A“’. Our study on the effect of cold hardening on glutathione (GSH) metabolism showed that chromosome 5A of wheat has an influence on the GSH accumulation and on the ratio of reduced and oxidised glutathione as part of a complex regulatory function during cold hardening. In addition, the level of increase in GSH content during hardening may indicate the degree of the frost tolerance of wheat.

Genetic study of glutathione accumulation during cold hardening in wheat.

The effect of cold hardening on the accumulation of glutathione (GSH) and its precursors was studied in the shoots and roots of wheat (Triticum aestivum L.) cv. Cheyenne (Ch, frost-tolerant) and cv. Chinese Spring (CS, moderately frost-sensitive), in a T. spelta L. accession (Tsp, frost-sensitive) and in chromosome substitution lines CS (Ch 5A) and CS (Tsp 5A). The fast induction of total glutathione accumulation was detected during the first 3 d of hardening in the shoots, especially in the frost-tolerant Ch and CS (Ch 5A). This observation was corroborated by the study of de novo GSH synthesis using [(35)S]sulfate. In Ch and CS (Ch 5A) the total cysteine, gamma-glutamylcysteine (precursors of GSH), hydroxymethylglutathione and GSH contents were greater during the 51-d treatment than in the sensitive genotypes. After 35 d hardening, when the maximum frost tolerance was observed, greater ratios of reduced to oxidised hydroxymethylglutathione and glutathione were detected in Ch and CS (Ch 5A) compared to the sensitive genotypes. A correspondingly greater glutathione reductase (EC 1.6.4.2) activity was also found in Ch and CS (Ch 5A). It can be assumed that chromosome 5A of wheat has an influence on GSH accumulation and on the ratio of reduced to oxidised glutathione as part of a complex regulatory function during hardening. Consequently, GSH may contribute to the enhancement of frost tolerance in wheat.

Characterization of Cold Hardening in Wheat Using Fluorescence Induction Parameters

Summary Two types of wheat varieties ( Triticum aestivum L. cv. Cheyenne and cv. Chinese Spring, with strong and poor frost resistance, respectively) and two substitution lines (Chinese Spring/Cheyenne 5A and Chinese Spring/Cheyenne 7A) were used in experiments to investigate the kind of changes that take place in the photosynthetic apparatus of different wheat genotypes as a consequence of growing at low temperature. Using a PAM fluorometer, changes iri the photochemical quenching were traced at 2 °C and 20 °C. Although there was generally less photochemical quenching at low temperature than at room temperature, in the case of the frost-resistant variety Cheyenne an increase in photochemical quenching was observed at low temperature as a function of the length of the hardening period. This seems to indicate the existence of a regulating mechanism that ensures that even at low temperature the plant will be capable of an adequate level of photosynthesis.

Accumulation of a High Molecular Weight Protein during Cold Hardening of Wheat (<italic>Triticum aestivum L.</italic>)

Accumulation of a High Molecular Weight Protein during Cold Hardening of Wheat (<italic>Triticum aestivum L.</italic>)

Properties of chloroplast membrane-bound ferredoxin--NADP + reductase during cold hardening of wheat. No indication of qualitative membrane changes during cold hardening.

Kinetic parameters of the chloroplastbound ferredoxin-NADP+ reductase from two varieties of wheat (Triticum aestivum), hardy Kharkov 22 MC (winter wheat) and less hardy Rescue (spring wheat), were followed during induction of frost hardiness as a means of examining possible changes in chloroplast membranes during hardening. No changes were found in the Michaelis constants for NADPH and 2,6-dichlorophenol indophenol, inhibition constants for p-chloromercuriphenylsulfonate, and activation energy values of the enzyme in either variety. The data suggest that no qualitative changes occurred in the properties of wheat chloroplast membranes related to ferredoxin-NADP+ reductase during cold hardening.

Comparative studies of activity and properties of ferredoxin–NADP+ reductase during cold hardening of wheat

Activity and properties of chloroplast ferredoxin–NADP− reductase (EC 1.6.7.1) were studied during cold hardening of two varieties of wheat (Triticum aestivnm), hardy Kharkov (winter wheat) and much less hardy Rescue (spring wheat), to determine whether adaptation to low temperatures involves changes in the activity and properties of this enzyme. Specific activity of ferredoxin–NADP− reductase increased during hardening of both varieties, but the increase was much greater in the more hardy variety, Kharkov 22 MC. No changes were found in the Michaelis constants for NADPH and 2,6-dichlorophenol indophenol, activation energy values, inhibition constants for p-chloromercuriphenylsulfonate, and sensitivity toward cold and heat inactivation of the enzyme from control and cold-hardened seedlings of both varieties. The data suggest that there is a preferential synthesis of ferredoxin–NADP− reductase during hardening of wheat, but the enzyme molecule remains unchanged.