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The effects of exogenous ABA on the expression of the cysteine proteinase (CP) gene and its inhibitor cystatin (WC3) in the leaves of winter wheat ( Triticum aestivum L.) seedlings that were hardened for 7 days at 5°C were studied. Seedling cold-hardiness was judged by the temperature causing death of 50% of palisade cells (LT) following 5-min freezing at the temperatures from −5 to −10°C. In the initial period of cooling, when seedling cold tolerance increased, the CP and WC3 gene expression increased considerably, but at the highest cold-hardiness the transcript levels of these genes returned to the control level. When ABA was applied exogenously, the CP gene expression grew by the order of magnitude already in 1-5 h from the onset of low temperature treatment and then abruptly dropped, but it was further maintained at a high level. In cold- and ABA-treated seedlings, the WC3 gene expression initially decreased, but it grew considerably in 3-7 days. It is concluded that the development of wheat cold-hardiness is related to ABA-regulated changes in the CP and WC3 gene expression. [ABSTRACT FROM AUTHOR]

The dynamics of cold resistance and the activity of the photosynthetic apparatus (PSA) of wheat germs at 4°C were studied. It was shown that in the first hours of cold, a certain functional readjustment to the changed conditions takes place in the plant organism. A decrease in the activity of the PSA and cessation of the linear growth of the leaf are registered at this stage along with an increase in resistance, as well as an increase in the coefficient of non-photochemical quenching of the fluorescence of chlorophyll. In one to four days, when resistance reaches its maximum, photosynthesis and the rate of electron transport are stabilized, the chlorophyll content in the lightcollecting complex increases, and the growth recommences. The final stage of adaptation (days 4-7) is characterized not only by the steady level of resistance but also by new functional organization of the PSA, which allows the plants to endure the lowered temperature successfully. [ABSTRACT FROM AUTHOR]

Changes in expression of WRKY transcription factor and stress protein genes ( Wcor15, Wrab17, Wrab19, and Wcs120) were studied on wheat ( Triticum aestivum L., cv. Moskovskaya 39) seedlings exposed to cold hardening for 7 days at 4°C. The high level of WRKY gene expression was noticed already in 15 min after the beginning of cold treatment, but the expression level lowered during longer treatments. Exogenous ABA (0.1 mM) suppressed the WRKY gene expression. The level of Wcor15 gene expression increased gradually, reaching the peak on the second day, and then decreased. Gene expression of Wrab17 remained elevated throughout the period of cold exposure (7 days), and expression of Wrab19 was promoted within the first two days. Exogenous ABA induced expression of Wcor15, Wrab17, and Wrab19 genes both at cold-hardening (4°C) and normal (22°C) temperatures. A significant increase in Wcs120 gene expression during cold hardening was ABA-independent. It is concluded that the increase of wheat plant resistance at the initial stage of cold hardening is related to gene expression of WRKY transcription factor and of stress proteins ( Wcor15, Wrab17, Wrab19, and Wcs120), while the resistance increase during prolonged adaptation is related to gene expression of Wcor15 and Wrab17. [ABSTRACT FROM AUTHOR]

The dynamics of amidase, cysteine protease, and trypsin inhibitor activities were studied in the leaves of wheat ( Triticum aestivum L.) seedlings grown under controlled conditions (25°C, illuminance 10 kLx, 14-h photoperiod) and subjected to cold hardening (5°C, 10 kLx, 14-h photoperiod). Changes in the activity of amidases and cysteine proteases proved to precede an increase in cold resistance during cold hardening and a decrease in cold resistance after the end of cold hardening. The activity of trypsin inhibitors changed only during cold hardening. It is suggested that amidases, cysteine proteases, and trypsin inhibitors are involved in the cold adaptation of plants. [ABSTRACT FROM AUTHOR]