Proline accumulation in response to high temperature in winter-acclimated shoots ofPrunus persica: a response associated with growth resumption or heat stress?

Abstract

Our previous study revealed that proline (Pro) accumulated in peach trees when cold-acclimated shoots were exposed to higher temperatures. In this study, we determined whether such Pro accumulation is indeed a high temperature-stress response or metabolic preparation for growth resumption. Two studies were conducted to address this question using 'Daewol' peach trees. In study 1 (February), Pro content of eco-dormant shoots increased when cold-acclimated plants were exposed to two heat treatments (HTs) but remained unchanged during the intervening cold treatment (CT). Concurrently, ornithine-delta-aminotransferase (OAT) and Δ 1-pyrroline-5carboxylate reductase (P5CR) genes were up-and down-regulated after two HTs and the CT, respectively. Study 2, conducted with growing trees (May), showed that Pro did not change and expression of P5CR and OAT was downregulated when trees were subjected to either HT or CT; HT and CT used here constituted 'stress' treatments as revealed by the decline in chlorophyll fluorescence. Taken together, these results suggest that Pro accumulation (study 1) may be associated with the preparation for growth resumption and not 'stress'. Furthermore, results from parallel gene expression studies suggest that the ornithine, rather than glutamate, pathway may be the primary Pro biosynthesis route both during growth resumption and high temperature stress in 'Daewol' peach.

Induced freezing tolerance and free amino acids perturbation of spinach by exogenous proline

“…Previous studies have reported that Pro synthesis is mainly stimulated via the Orn pathway under abiotic stress and spring growth resumption in some species (Lee and Chang 1999;Shin et al 2016). However, in our results, Orn was not detected due to its very small amount.…”

“…On the other hand, Pro accumulation does not necessarily lead to dehydration or saltstress tolerance in Arabidopsis thaliana (Liu and Zhu 1997;Nakashima et al 1998). In our previous studies, contrary to our expectations largely based on published reports of Pro accumulation in response to cold stress in various herbaceous species (Chu et al 1974;Duncan and Widholm 1987;Savouré et al 1997;Hur et al 2004), Pro accumulation of peach shoots was likely a response to activation of metabolism associated with growth resumption in eco-dormant shoots at relatively high temperatures to be conducive for growth (Shin et al 2016). Therefore, the relationship between Pro accumulation and abiotic stress tolerance in plants does not seem to be universal.…”

Comparative transcriptomic analysis reveals common molecular factors responsive to heat and drought stress in Agrostis stolonifera

“…P5CS enzyme activity in sorghum ( Sorghum bicolor ) seedlings was found to be induced upon short-term heat stress (6 h at 40 °C) 52 , but inhibited under long-term heat stress, such as in wheat (5 d at 33 °C) 53 , and tomato ( Solanum lycopersicum ) (48 h at 35 °C) 54 . Similarly, transcript levels of P5CS were up-regulated by short-term heat stress in Nitraria tangutorum (6 h at 50 °C) 55 , but down-regulated by long- term heat stress in peach ( Prunus persica ) (5 d at 36.7 °C) 56 . The common up-regulation of proline synthesis by both long-term (21 d) heat and drought stress in this study suggested the importance of P5CS regulation of proline synthesis in A. stolonifera adaptation to prolonged heat and drought stress.…”

Metabolome Profiling of Heat Priming Effects, Senescence, and Acclimation of Bread Wheat Induced by High Temperatures at Different Growth Stages

“…Proline is known to be a compatible solute that increases cell osmotic pressure under drought stress [ 3 ]. However, the role of proline in high-temperature stress is evident but not yet fully understood [ 24 ].…”