Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

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R.G. Trischuk, B.S. Schilling, M. Wisniewski and L.V. Gusta
species had measurable peroxidase activity in only AC plants. Similar measurements
were conducted for invertase in NA and AC wheat, identifying that alterations in protein
structure occurred as a result of cold acclimation (Roberts, 1974). The altered form
of the enzyme present in CA wheat exhibited different kinetic properties (i.e. was more
efficient at LT) and therefore functionally replaced the lower molecular weight form
present in NA seedlings (Roberts, 1978). Similar alterations in enzyme conformation
were also observed in fully acclimated alfalfa plants, where shifts in the structure of
several dehydrogenases involved in the respiratory pathway enabled them to function
at LT (Krasnuk et al., 1975, 1976, 1976a). Based on this discovery the activity, structure
and stability of many enzymes were measured in NA and AC tissues of a multitude of
species with similar results (Huner et al., 1976, 1978, 1979, 1981; Griffith et al., 1985).
In the late 1940’s it was realized that total protein content changes in response
to LT when levels of soluble proteins were measured in bark cells of black locust
(Robinia pseudoaccia L) (Siminovitch and Briggs, 1949). In this study, total soluble
protein content was higher in fully acclimated bark. To expand this study, measurements
were taken at each season in a year, demonstrating that total protein content
increases in autumn closely paralleling increases in freezing tolerance (Siminovich and
Briggs, 1953). Protein levels were maintained over the winter months dropped as the
temperature increased in spring and dormancy was broken. Seasonal changes in total
protein content have since been reported in many other species (Parker, 1962; Coleman
et al., 1966; Gerloff et al., 1967; Pomeroy et al., 1970; Chen and Li, 1980; and Guy and
Haskell, 1987) similar but not universal responses have been observed. These studies
also led to the realization that protein changes in response to low temperature exposure
were not only quantitative but also qualitative (Siminovich and Briggs, 1953), as it was
realized that the proteins synthesized in plants exposed to LT were not identical to
those isolated from NA tissues (McGown et al., 1968; Cracker at al., 1969; Davis and
Gilbert, 1970; Faw and Jung, 1972; Brown and Bixby, 1975; Faw et al., 1976; Huner at al.,
1976; Kacperska-Palacz et al., 1977; Rosas et al., 1986). The general consensus of these
studies indicated that a subset of LT proteins were synthesized in addition to those
present in NA tissues, but these were difficult to detect with present day electrophoretic
methods.
As early as 1970, Weiser hypothesized that cold acclimation resulted in the
expression of a novel set of genes not expressed in NA plants (Weiser, 1970). This
hypothesis has since been proven in a variety of independent studies (Marmiroli et al.,
1986; Yacoob and Filion, 1986, 1986a; Meza-Basso et al., 1986, Johnson-Flanagan and
Singh, 1987; Guy and Haskell, 1987, 1988; Johnson-Flanagan and Singh, 1987; Laroch
and Hopkins, 1987; Mohapatra et al, 1987; Ougham, 1987; Robertson et al., 1987; Sarhan
and Perras, 1987; Tseng and Li, 1987; Cooper and Ort, 1988; Kurkela et al., 1988; Hahn
and Walbot, 1989; Perras and Sarhan, 1989). Careful examination of the proteins that
accumulate in response to LT exposure in many different species has revealed the
appearance and decline of similar classes and types of proteins. These proteins are,
however, significantly less conserved than those that arise as a result of heat shock