Somatic Embryogenesis in Pines

Assessment of alternative freezing methods for preservation at -80 °C of radiata pine embryogenic cultures: A six-year study

Somatic embryogenesis is an essential component of breeding programs for Pinus radiata aimed at implementing multi-varietal forestry. Coupled with this technique, the long-term cryopreservation of embryogenic cultures is necessary to maintain the viability of the cell lines, but this entails high maintenance costs. In this research we evaluated the application of a protocol for long-term storage at -80 °C in an ultra-low freezer to preserve several radiata pine embryogenic cell lines. Also, we studied the influence of several parameters to optimize the protocol, such as the effect of dimethyl sulfoxide cryoprotectant solution, the effectiveness of alternative freezing methods, the use of post thawing treatments and the addition of sodium butyrate at maturation stage. We found that the use of dimethyl sulfoxide cryoprotectant enhanced somatic embryo production; slow cooling was the only viable method for preserving embryogenic cell lines at -80 °C and the use of sodium butyrate was not highly effective to improve maturation and germination stages. Moreover, we have regenerated embryogenic cell lines up to their conversion into plants after six years of storage. In line with these findings, the protocol to storage in an ultra-low freezer represents an economical alternative to preserve somatic embryogenic cultures of Pinus radiata.

Testing Explant Sources, Culture Media, and Light Conditions for the Improvement of Organogenesis in Pinus ponderosa (P. Lawson and C. Lawson)

Pinus. ponderosa (P. Lawson and C. Lawson) is a commercial tree and one of the most important forest species in North America. Ponderosa pine suffers hardship when going through vegetative propagation and, in some cases, 15-30 years are needed to achieve full reproductive capacity. Based on previous works on P. ponderosa regeneration through in vitro organogenesis and trying to improve the published protocols, our objective was to analyze the influence of different types of explants, basal culture media, cytokinins, auxins, and light treatments on the success of shoot multiplication and rooting phases. Whole zygotic embryos and 44 µΜ 6-benzyladenine showed the best results in terms of explants survival. For shoot organogenesis, whole zygotic embryos and half LP (LP medium, Quoirin and Lepoivre, 1977, modified by Aitken-Christie et al., 1988) macronutrients were selected. A significant positive interaction between whole zygotic embryos and half LP macronutrients was found for the percentage of explants forming shoots. Regarding the light treatments applied, a significantly higher percentage of shoots elongated enough to be rooted was detected in shoots growing under blue LED at a light intensity of 61.09 µmol m^-2 s^-1. However, the acclimatization percentage was higher in shoots previously cultivated under fluorescent light at a light intensity of 61.71 µmol m^-2 s^-1. Anatomical studies using light microscopy and scanning electron microscopy showed the light treatments promoted differences in anatomical aspects in in vitro shoots; needles of plantlets exposed to red and blue LEDs revealed less stomata compared with needles from plantlets exposed to fluorescent light.

Proteomics research in forest trees: A 2012-2022 update

This review is a compilation of proteomic studies on forest tree species published in the last decade (2012-2022), mostly focused on the most investigated species, including Eucalyptus, Pinus, and Quercus. Improvements in equipment, platforms, and methods in addition to the increasing availability of genomic data have favored the biological knowledge of these species at the molecular, organismal, and community levels. Integration of proteomics with physiological, biochemical and other large-scale omics in the direction of the Systems Biology, will provide a comprehensive understanding of different biological processes, from growth and development to responses to biotic and abiotic stresses. As main issue we envisage that proteomics in long-living plants will thrive light on the plant responses and resilience to global climate change, contributing to climate mitigation strategies and molecular breeding programs. Proteomics not only will provide a molecular knowledge of the mechanisms of resilience to either biotic or abiotic stresses, but also will allow the identification on key gene products and its interaction. Proteomics research has also a translational character being applied to the characterization of the variability and biodiversity, as well as to wood and non-wood derived products, traceability, allergen and bioactive peptides identification, among others. Even thought, the full potential of proteomics is far from being fully exploited in forest tree research, with PTMs and interactomics being reserved to plant model systems. The most outstanding achievements in forest tree proteomics in the last decade as well as prospects are discussed.