Genetic stability, amino acid, and polyamine profile analyses in radiata pine somatic embryos maturated at high temperatures

Applying stress factors such as high temperatures during the different stages of somatic embryogenesis is important to uncover the molecular mechanisms of stress response and adaptation, and as a strategy to produce plants adapted to harsh environmental conditions derived from climate changes. In this sense, the present work aims to study the effect of high temperatures applied during the maturation of somatic embryogenesis in the ploidy stability, the amino acid and polyamine profiles of the somatic embryos obtained, and the morphological characteristics of the somatic plantlets. The results revealed that the maturation temperature did not affect the morphology of the resulting somatic plantlets, nor the ploidy and genome size of phenotypically normal somatic embryos, whose ploidy and DNA content levels were similar to those found in mature zygotic embryos. Nonetheless, a slight but significant reduction of the genome size of aberrant somatic embryos was observed. The maturation temperature changed the levels of glycine, arginine, lysine, and ornithine. These last three amino acids are precursors of the polyamines detected. Regarding this, putrescine levels were higher in somatic embryos from the highest maturation temperature (5 min pulse at 60 oC), however, the amount of this polyamine in all samples was much lower than spermidine, spermine and cadaverine. In conclusion, the different temperatures applied did not lead to substantial changes in the ploidy level, endogenous PAs of the somatic embryos developed, or in the morphology of the somatic plantlets. Significant changes in the endogenous amino acids were observed, which may be linked to PAs metabolism and other metabolic pathways involved in stress response. Maturation temperature doesn ' t affect ploidy levels of radiata pine somatic embryos, however, it affects the endogenous levels of glycine, arginine, lysine, and putrescine.