Вплив температури вирощування та сахарози на активність аскорбат пероксидази у Arabidopsis thaliana в умовах теплового стресу

Abstract

Досліджено вплив екзогенної сахарози та температури вирощування на активність аскорбат пероксидази (APX) у листках арабідопсису за дії теплового стресу. Доведено, що для рослин, які зростали при 20ºС присутність сахарози в інкубаційному буфері необхідна для стабілізації АРХ і за умов помірного (37ºС) теплового стресу, тоді як у рослин, що культивувались за 28ºС, фермент залишався стабільним і за відсутності сахарози. За дії жорсткого теплового стресу підвищена температура попереднього культивування та присутність сахарози у буфері є факторами, які забезпечують часткову стабілізацію АРХ.

Исследовано влияние экзогенной сахарозы и температуры выращивания на активность аскорбат пероксидазы (APX) в листьях арабидопсиса под воздействием теплового стресса. Доказано, что для растений, которые росли при 20ºС, присутствие сахарозы в инкубационном буфере необходимо для стабилизации АРХ и в условиях умеренного (37ºС) теплового стресса, тогда как у растений, культивируемых при 28ºС, фермент оставался стабильным и в отсутствие сахарозы. В условиях жесткого теплового стресса повышенная температура предварительного культивирования и присутствие сахарозы в буфере являются факторами, обеспечивают частичную стабилизацию АРХ.

An increase of environmental temperature (heat stress) results in denaturation of proteins. In response, numerous heat shock proteins (HSP), some of which represent molecular chaperones, are expressed in the plant cell. The HSP can protect other proteins from denaturation. In addition to chaperones, different low molecular compounds including disaccharides are also involved in stabilization of proteins upon high temperature. Also, elevated temperatures enhance the generation of reactive oxygen species. This is accompanied by activation of protective antioxidant enzymes, in particular ascorbate peroxidase (APX). The influence of exogenous sucrose and growth temperature on the activity of APX in the Arabidopsis leaves upon heat stress has been investigated. In the absence of sucrose in the incubation buffer, moderate stress treatment (37°C for 4 hours) decreased the APX activity by 29% in plants previously grown at 20°C. In the presence of sucrose or in plants cultivated at 28°C no decrease of the enzyme activity was found. After 2 hours of severe stress treatment (44°C) in the presence of sucrose, a decrease in APX activity by 72% and 65% was observed in plants cultivated, respectively, at 20°C and 28°C. The activity of the enzyme decreased even more after 4 hours of stress treatment: in the leaves of plants constantly grown at 20°C, the residual activity of APX was only 16% of the activity detected in control samples, whereas in plants grown at 28°C, the residual activity was 25%. A more significant decrease in APX activity was detected in the samples exposed to 44°C in the absence of sucrose. In particular, decreasing of activity by 81% and 70% was detected after 2 hours of treatment for plants cultivated at 20°C and 28°C. Similar, the decrease in enzyme activity was 92% and 87% after 4 hours of severe heat stress. It was also demonstrated that after severe stress treatment (4h 44ºC), the APX activity was (1) 1.6-1.8 times higher in plants cultivated at 28ºС and (2) 1.8-2.0 times higher in leaves that were incubated in the presence of sucrose. Thus, it has been proven that for plants that were grown at 20°C, the presence of sucrose in the incubation buffer is necessary for thermal stabilization of APX activity upon moderate (37°C) heat stress. In contrast, in plants pre-cultivated at 28°C the enzyme remained active in the absence of sucrose. Elevated cultivation temperature and the presence of sucrose in the incubation buffer are factors that provide partial stabilization of APX upon severe heat stress.