Caracterização fisiológica e análise proteômica comparativa de Eucalyptus spp. submetidos a estresses abióticos

Abstract

Eucalypt has been widely cultivated in several regions of the world due to its good adaptability to different climatic conditions and easy use in plant breeding programs.Since water and salt stress are the main factors that affect plants development, studying their effect on germination and initial growth of seedlings become relevant. In order to determine the species with the most contrasting behavior regarding the ability to tolerate water and salt stress, germination tests with six eucalypt species (E. saligna, E. brassiana, E. tereticornis, E. camaldulensis, E. urophylla e E. grandis) at different osmotic potentials, obtained by aqueous solutions of PEG and NaCl, were performed to simulate water and salt stress. Radicle protrusion was counted daily while normal seedlings were counted at the end of the tests (45 days). Generalized linear model analysis was used and the data were analyzed by the LSD test at 5% probability. It was verified that the maximum limit of tolerance to water stress ranged from -0.6 to -0.8 MPa for the six studied species. E. urophylla and E. tereticornis were more tolerant to drought while E. camaldulensis and E. tereticornis were the most tolerant to salt stress during germination. In addition, the present study also aimed to characterize the physiological responses of young plants of these six Eucalyptus species, from contrasting environments in terms of water availability, submitted to different water regimes. For this, 180 days old seedlings were transplanted into pots, where they remained for 85 days in a non-climatized greenhouse. After the adoption of water regimes of 40, 60 and 80% of field capacity (FC) for eight days, the following variables were analyzed: liquid photosynthesis, transpiration, stomatal conductance and leaf water potential, in addition to collection of leaves for proteomic analysis. A reduction in these variables was observed for all species as water stress intensified, however, this reduction was less marked in E. saligna species. At 40% of FC, E. tereticornis was the only one to present plant mortality (57%).Among the six species studied, E. saligna was the most tolerant to water stress followed by E. urophylla and E. camaldulensis, while E. tereticornis was the most sensitive, followed by E. brassiana and E. grandis.The proteomic analysis was performed between the two most contrasting species, submitted or not to water stress. For this, total protein extraction was proceeded from leaves of E. saligna and E. tereticornis maintened at40 and 80% of FC (control). The proteins were separated by two-dimensional electrophoresis with subsequent identification of those differentially abundant by mass spectrometry.Comparative proteomics allowed to identify that such proteins may play a crucial role in water stress tolerance in E. saligna through the identification of species-specific proteins and potential stress tolerance markers such as ATP synthase gamma, ATP synthase alpha, glutamine synthetase and a vacuolar protein.