Changes in the sugar management in response to dehardening as the one of thecauses of frost tolerance disorders in winter oilseed rape
Oilseeed rape (Brassica napus ssp. Oleifera L.) belongs to the group of oilseeds and is one of the most important sources of vegetable oil in the world. Rapeseed oil is a high-quality vegetable fat as well as a valuable forage source. In the structure of sown crops in Poland, winter oilseed rape is one of the most commonly cultivated species. Winter cultivars give a higher yield than spring ones, but part of their vegetation is in the winter months, which is associated with the risk of frost injuries. Natural adaptation of winter oilseed rape to growth in conditions of low temperatures is based on the ability of this species to metabolic changes and to hardening (acclimation) to low temperature. This requires the plants to be exposed to cold temperatures, which further increases their tolerance to frost. In recent years, due to the progressive climate change and global warming, weather anomalies have appeared more and more often, an example of which is the occurrence of periods of elevated temperature in late autumn and winter (sometimes even up to 20oC). Several days of elevated temperature disrupts the process of cold acclimation (cold hardening) and reduces the plant's tolerance to frost - the deacclimation (dehardening) process takes place.
During the cold acclimation, a lot of biochemical and metabolic changes take place, where key elements are changes in the sugar management. Sugars play an essential role in the process of properly running cold acclimation. At cold , level of sugars increase, because they play role as osmoregulators and cryoprotectants. The good wintering of plants (including tolerance to frost) is associated with the accumulation of sugars during acclimation at low temperatures, and then their gradual use in winter. However, during deacclimation sugars start to be metabolized much faster. As a result of this, among other the potential of cell juice is changed. It affects the plant's survival during frost, which can occur after the high temperature period.
As part of this project, it is planned to determine the profile and distribution of sugars soluble in different parts of the plant (winter oilseed rape). In order to characterize the mechanisms of the sugar management will be performed the measurements of the activity of important enzymes - sucrose synthase (SUS) and sucrose phosphate synthase (SPS). These enzymes play pivotal role in the biosynthesis/transport of sucrose. Moreover, the accumulation of the SUS1 and SPS proteins (by immunoblotting) and the accumulation of the SUT1 and SWEET11 (RT-PCR) transcripts will be determined. The results should provide new knowledge on the deacclimation mechanisms and will allow to characterize a part of the sugar management of oilseed rape in response to deacclimation. This knowledge may be useful in the future, for example, for creating new cultivars - more tolerant to dehardening and more tolerant to frost in the conditions of a changing climate.