Brassinosteroids increase winter survival of winter rye (Secale cereale L.) by affecting photosynthetic capacity and carbohydrate metabolism during the cold acclimation process

Abstract

The aim of the study was to verify the hypothesis that brassinosteroids would modify the cold acclimation process through the stimulation of photosynthesis and carbohydrate metabolism, and would consequently cause an increase in the plant's capacity for winter survival. Seedlings of two winter rye cultivars (winter-resistant and moderately winter-resistant types) were sprayed with 24-epibrassinolide (EBR) and then subjected to cold acclimation at 4°C. The foliar hormone application was studied for its effects on two components of winter resistance: tolerance to frost; and resistance to snow mould. These were examined after medium (3 weeks) and long (6 weeks) terms of cold acclimation. Additionally, as a control group, the level of endogenous brassinosteroids was measured in non-treated plants. The maximum acquired snow mould resistance was observed in the EBRtreated plants after 3 weeks of cold acclimation, while the maximum frost tolerance was recorded after 6 weeks of cold acclimation, as compared with control. In the winterresistant cultivars, the EBR-induced snow mould resistance coincided with a lower photosynthetic efficiency and a lack of change in their Rubisco activity and level of total soluble carbohydrates. The elevated EBR-induced frost tolerance in the winter-resistant cultivars was associated with a carbohydrate metabolism that promoted a decrease in the monosaccharides of the leaves that stimulate photosynthetic efficiency and Rubisco activity. For both cultivars, the control plants developed frost tolerance between the third and sixth week of cold acclimation. However, the winter-resistant cultivar was characterised by a constant castasterone (CS) level, while the moderately winter-resistant one experienced a sharp increase in its endogenous CS after 3 weeks, and then after 6 weeks of cold acclimation.

Involvement of homocastasterone, salicylic and abscisic acids in the regulation of drought and freezing tolerance in doubled haploid lines of winter barley

“…ABA abscisic acid, SA salicylic acid, HCS homocastasterone, CS castasterone, TE teasterone, DL dolicholide, Sc control seedlings/heading plants sensitive to freezing/drought treatment, Tc control seedlings/heading plants tolerant to freezing/drought treatment, S H cold hardened seedlings sensitive to freezing stress, T H cold hardened seedlings tolerant to freezing stress, S D drought treated plants sensitive to drought stress, T D drought treated plants tolerant to drought stress 1 3 freezing tolerance, whereas disturbances in later stages of BR biosynthesis had no effect. According to literature, the content of BRs increased in cold hardened winter rye (Pociecha et al 2016) and spring barley (Sadura et al 2019), which is to some extent in accordance with data obtained in this study as significant increase in HCS content was noted for more freezing tolerant DH lines of barley. Previous studies with spring barley (Sadura et al 2019) and winter wheat (Janeczko et al 2019) also showed that cultivars less tolerant to freezing accumulated lower amounts of BRs (especially HCS) in response to cold hardening in comparison with more tolerant cultivars.…”

Physiological and molecular mechanisms of brassinosteroid-induced tolerance to high and low temperature in plants

“…This phenomenon did not occur during recovery under irradiance of 100 μmol m -2 s -1 . An increase in Rubisco activity after 24-epibrassinolide application was also confirmed by Pociecha et al (2016) in a study on winter rye plants exposed to 3 and 6 weeks of cold. On the other hand, in perennial ryegrass, when 24-epibrassinolide (0.25 mg dm -3 ) was applied before plant exposure to 4 ºC for 6 weeks, the Rubisco activity was reduced by about 30 % but only in sensitive cv.…”

“…in plants grown at 26 °C. In turn, Pociecha et al (2016) showed that the castasterone content in rye grown at 18 °C is 4 -5 pmol g -1 (f.m. ), however, as a result of six weeks of cold, this content increases to about 14 -16 pmol g -1 (f.m.).…”

“…) BR concentration (modified from Wang et al 2014 andLi et al 2017). Brassinosteroid concentrations are exemplary given for rye based on Pociecha et al (2016); P -phosphate. +P -phosphorylation, -P -dephosphorylation, P -phosphate attached to the protein or not attached to protein.…”

Mutations in the HvDWARF, HvCPD and HvBRI1 Genes-Involved in Brassinosteroid Biosynthesis/Signalling: Altered Photosynthetic Efficiency, Hormonal Homeostasis and Tolerance to High/Low Temperatures in Barley

“…After this period, the plant survival rate was estimated based on the Larsen (1978) visual scale (0-9 scale of regrowth after frost treatment), where 0 indicates completely dead plants with no signs of leaf elongation, whereas 9 means no symptoms of injury. For a detailed description of the scale see Pociecha et al (2016).…”