Constitutive and Cold Acclimation-Regulated Protein Expression Profiles of Scots Pine Seedlings Reveal Potential for Adaptive Capacity of Geographically Distant Populations

Geographically distant Scots pine (Pinus sylvestris L.) populations are adapted to specific photoperiods and temperature gradients, and markedly vary in the timing of growth patterns and adaptive traits. To understand the variability of adaptive capacity within species, molecular mechanisms that govern the physiological aspects of phenotypic plasticity should be addressed. Protein expression analysis is capable of depicting molecular events closely linked to phenotype formation. Therefore, in this study, we used comparative proteomics analysis to differentiate Scots pine genotypes originating from geographically distant populations in Europe, which show distinct growth and cold adaptation phenotypes. Needles were collected from 3-month-old seedlings originating from populations in Spain, Lithuania and Finland. Under active growth-promoting conditions and upon acclimation treatment, 65 and 53 differentially expressed proteins were identified, respectively. Constitutive protein expression differences detected during active growth were associated with cell metabolism and stress response, and conveyed a population-specific adaptation to the distinct climatic conditions. Acclimation-induced protein expression patterns suggested the presence of a similar cold adaptation mechanism among the populations. Variation of adaptive capacity among the genotypes was potentially represented by a constitutive low level of expression of the Ser/Thr-protein phosphatase, the negative regulator of the adaptive response. Also, overall less pronounced acclimation-induced response in seedlings from the Spanish population was observed. Thus, our study demonstrates that comparative proteomic analysis of young conifer seedlings is capable of providing insights into adaptation processes at the cellular level, which could help to infer variability of adaptive capacity within the plant species.