Stress regulating rroperties of two Bacillus sp. bacterial endophytes in apple (Malus × domestica Borkh.) culture in vitro

Abstract

Vegetative propagation methods are commonly used for horticultural plants of Rosaceae family, such as apple, pear, cherry, peach and strawberry. Development of in vitro micropropagation is important for plant biotechnology research and agricultural applications. In vitro environment imposes unfavorable conditions that lead to imbalance of plant physiological equilibrium and induction of oxidative stress, which occurs via production and accumulation of reactive oxygen (ROS) species. ROS cause lipid peroxidation leading to membrane injury, enzyme inactivation and DNA damage. It has been demonstrated that endophytic microorganisms play important role in plant acclimation and stress response. However, capacity of endophytes to modulate plant stress responce under in vitro conditions is largerly unexplored. Therefore the aim of this study was to assess effect of two endophytic Bacillus sp. bacteria strains (Da4 and Oa4) on ROS production and gene expression in apple cell suspension and stress reducing properties in shoot culture in vitro. Our study revealed that the two endophytic bacteria strains associated to apple cv. Gala cells in suspension (Fig. 1), and demonstrated different intracellular ROS production regulating properties (Fig. 2). Protein expression analysis using DIGE revealed that incubation of the cells with ROS production inhibiting strain Oa4 resulted in highly increased abundance of 29 proteoforms involved in defense response, metabolic and oxidation – reduction processes (Fig. 3). Meanwhile 12 and 25 proteins of increased or decreased abundance, respectively, were detected after incubation with either of the endophytic strains. In apple cv. Gala shoot culture, ROS production was mostly detectable in leaf and injured tissues (Fig. 4). Lipid peroxidation analysis established that oxidative damage was the most prominent during first week after replanting and during onset of senescence of the culture (Fig. 5).[...]