The effect of proline applicotions on heat shock proteins in pepper plant under low temperatureconditions

In this study investigating the effects of proline treatments on heat shock proteins (HSP) in pepper plant (Capsicum annuum L.) under low temperature stress, seeds of 'Yalova Çorbacı 12' pepper variety were planted in 45-well viols containing a mixture of peat, soil and perlite (1:1:1). Seedlings were grown in a controlled greenhouse at 25/18 °C (day/night) and 60±5% humidity, 16 hours light/8 hours dark, until 3-4 leaf stage. 0 mM, 5 mM, 10 mM and 20 mM of the proline solution was applied as a foliar spray 3 times, once every three days. At the end of the trail, the plants were exposed to +8 °C temperature, 16 hours light / 8 hours dark for 3 days at low temperature. Mean while, the control plants were left in the controlled greenhouse. Cellular damage, proline amount, total soluble protein (TSP) amount were determined in leaf tissues of pepper plants, SDS PAGE and immunoblot analyzes were performed. It was determined that the damage in plants without proline (0 mM) at low temperature stress was higher than in plants treated with proline. In plants treated with proline, the lowest damage was observed at 5 mM, followed by 10 and 20 mM treatments, respectively. The proline amount of plants under low temperature decreased at 0 mM proline treatment, and increased in the other plants treated with proline, when compared with the control plants. It was observed that low temperature stress decreased TSP amount in all practices, but the amount of TSP in proline-treated plants was higher than in nonproline-treated plants. Among the plants subjected to low temperature stress, the highest amount of TSP was obtained from the 5 mM proline-treated plants. In SDS PAGE, protein bands varying in size from 17 kDa to 40 kDa were detected according to the treatments. According to the immunoblot analysis, it was determined that the density of the 40 kDa HSP 60 generally increased in plants under low temperature stress, and the most intense HSP 60 synthesis was in the 5 mM ptoline treatment. HSP 23 with a size of 23 kDa showed a similar increase in plants under low temperature stress, reaching the highest level in 5 mM proline treatment, similar to HSP 60. It has been determined that HSP 60 and HSP 23 are effective in increasing plant stress tolerance in pepper plants under low temperature stress and 5 mM proline treatment is the most appropriate concentration that can help to gain tolerance.