The dynamics of the levels of cytoplasmic HSP70 and chloroplast HSP70B chaperones under heat stress differs in three species of pumpkin with different resistance to stress

The first line of defense in plants under stress is the cell chaperone system. In this work, we studied the effect of heat stress on the levels of cytoplasmic chaperones HSP70 and HSP70B in chloroplasts of three species of Cucurbita (C. maxima Duchesne, C. pepo L. and C. moschata Duchesne), which differ in resistance to stress. A relationship has been established between the levels of chaperones HSP70 in the cytoplasm and HSP70B in chloroplasts and the species of pumpkin plants under heat stress conditions. Under stress, a significant increase in the level of chaperones was observed in the cells of pumpkin plants C. maxima – the level of HSP70 in the cytoplasm increased by 3.6 times, and the level of HSP70B in chloroplasts – by two times. Heat stress caused a 1.7-fold increase in the level of the cytoplasmic chaperone HSP70 in the cells of C. pepo pumpkin plants, but no significant change in the level of the HSP70B protein was noted. However, as a result of the effect of heat stress on C. moschata pumpkin plants, a decrease in the levels of HSP70 and HSP70B was revealed compared to untreated plants. The dynamics of changes in the levels of chaperones in the cytoplasm and chloroplasts under the influence of heat stress are similar. It should be noted that the constitutive level of HSP70 and HSP70B under normal conditions in C. moschata and C. repo is higher than in C. maxima. Analysis of the data obtained revealed an interesting pattern: high constitutive levels of HSP lead to insignificant induction of HSP and vice versa – low constitutive level of these proteins correlates with high induction of these proteins after heat stress. The data obtained are important for understanding the mechanisms of plant resistance to stress and can be useful for the selection and creation of highly resistant productive varieties of agriculturally important plants.