Effect of Thermal Stress on Tissue Ultrastructure and Metabolite Profiles During Initiation of Radiata Pine Somatic Embryogenesis

Abstract

Climate change will inevitably lead to environmental variations, thus plant drought tolerance will be a determinant factor in the success of plantations and natural forestry recovery. Some metabolites, such as soluble carbohydrates and amino acids, have been described as being the key to both embryogenesis efficiency and abiotic stress response, contributing to phenotypic plasticity and the adaptive capacity of plants. For this reason, our main objectives were to evaluate if the temperature during embryonal mass initiation in radiata pine was critical to the success of somatic embryogenesis, to alter the morphological and ultrastructural organization of embryonal masses at cellular level and to modify the carbohydrate, protein, or amino acid contents. The first SE initiation experiments were carried out at moderate and high temperatures for periods of different durations prior to transfer to the control temperature of 23°C. Cultures initiated at moderate temperatures (30°C, 4 weeks and 40°C, 4 days) showed significantly lower initiation and proliferation rates than those at the control temperature or pulse treatment at high temperatures (50°C, 5 min). No significant differences were observed either for the percentage of embryogenic cell lines that produced somatic embryos, or for the number of somatic embryos per gram of embryonal mass. Based on the results from the first experiments, initiation was carried out at 40°C 4 h; 50°C, 30 min; and a pulse treatment of 60°C, 5 min. No significant differences were found for the initiation or number of established lines or for the maturation of somatic embryos. However, large morphological differences were observed in the mature somatic embryos. At the same time, changes observed at cellular level suggested that strong heat shock treatments may trigger the programmed cell death of embryogenic cells, leading to an early loss of embryogenic potential, and the formation of supernumerary suspensor cells. Finally, among all the differences observed in the metabolic profile, it is worth highlighting the accumulation of tyrosine and isoleucine, both amino acids involved in the synthesis of abiotic stress response-related secondary metabolites.

Induction of Radiata Pine Somatic Embryogenesis at High Temperatures Provokes a Long-Term Decrease in DNA Methylation/Hydroxymethylation and Differential Expression of Stress-Related Genes

“…In [2] they observed GDM rates lower than 5% in similar-aged EMs of radiata pine and results in Pinus nigra underlined that the formation of bipolar structures in EMs can only be obtained when 5mC levels are not higher than 18% [32]. Nonetheless, micromorphological analyses carried out in our laboratory confirmed the presence of polarised structures presenting different developmental and organizational stages under similar culture conditions in radiata pine [24].…”

“…Other studies have reported enhanced synthesis of this enzyme during heat stress in radiata pine and linked its accumulation with the production of secondary metabolites like flavonoids [59]. The presence of these last compounds was remarked in previous studies after heat exposure in EMs [24].…”

Different MicroRNA Families Involved in Regulating High Temperature Stress Response during Cotton (Gossypium hirsutum L.) Anther Development

“…In this strategy, high-abundance miRNAs in the HT-tolerant line, including the members of the miR160, miR167, and miR2949 families (ghr-novel-miR160b-5p > ghr-novel-miR160c-5p, ghr-miR167a > ghr-miR167b, and ghr-miR2949a-5p) were downregulated ( Figure 5), contributed to the accumulation of energy substances in cells, and ensured the proliferation of pollen mother cells. However, certain concentrations of secondary metabolites and fatty acids can increase the tolerance of cells to HT [32,33]. The SCP anthers suffered from HT stress, which can disturb cell energy metabolism and redox balance in the HT-sensitive line and eventually lead to male sterility.…”

“…Meiosis is the period that is most sensitive to heat stress [39][40][41]. The accumulation of secondary metabolites in cells helps increase the heat tolerance of plants under HT stress [33,42]. Heat stress tolerance is a comprehensive process that requires multiple factors to achieve a dynamic balance.…”

A comprehensive analysis to understand the mechanism of action of balneotherapy: why, how, and where they can be used? Evidence from in vitro studies performed on human and animal samples

“…Furthermore, it is necessary to underline that the beneficial effects of BT in vivo are partially related to the temperature of the mineral water, while all the above-described in vitro studies have been performed at the physiological temperature of 37°C, because supraphysiological temperatures could represent a source of bias in terms of cell viability and metabolism (Castander-Olarieta et al 2019;Kaplan et al 2003;Mead et al 2012).…”