Abstract
Interactions between host plants and endophytic microorganisms play an important role in plant responses to pathogens and environmental stresses and have potential applications for plant stress management under in vitro conditions. We assessed the effect of endophytic bacteria on the growth and proliferation of domestic apple cv. Gala shoots in vitro. Further, a model apple cell suspension system was used to examine molecular events and protein expression patterns at an early stage of plant–endophyte interaction. Among the seven strains used in the study, Bacillus spp. strains Da_1, Da_4, and Da_5 and the Pseudomonas fluorescens strain Ga_1 promoted shoot growth and auxiliary shoot proliferation. In contrast, Bacillus sp. strain Oa_4, P. fluorescens strain Ga_3 and P. orientalis strain G_12 inhibited shoot development. In the cell suspension, the effects of the association between endophytic bacteria and plant cells were specific to each strain. Modulation of the cellular redox balance was monitored in the apple cells using a 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) probe, and strain-specific effects were observed that correlated with the in vitro shoot development results. Proteomic analysis revealed differences in protein expressions in apple cells co-cultivated with different Bacillus spp. strains that had contrasting effects on cellular redox balance and shoot development. The Bacillus sp. strain Da_4, which enhanced shoot development and oxidation of H2DCFDA, induced differential expression of proteins that are mainly involved in the defense response and regulation of oxidative stress. Meanwhile, treatment with Bacillus sp. strain Oa_4 led to strong upregulation of PLAT1, HSC70-1 and several other proteins involved in protein metabolism and cell development. Taken together, the results suggest that different cell signaling and response events at the early stage of the plant–endophyte interaction may be important for strain-dependent regulation of cellular redox balance and development of shoot phenotype.
Highlights
Plant micropropagation in vitro has various applications in germplasm storage, industrial scale production of vegetatively propagated plants, plant biology research, and genetic transformations
Our study revealed contrasting effects of bacterization with selected endophytic bacteria strains of Bacillus and Pseudomonas spp. on apple shoot biomass accumulation and proliferation of auxiliary shoots in vitro
The stimulating or suppressing effect was not related to bacterial species or genus but varied depending on the specific bacterial strain (Figure 1)
Summary
Plant micropropagation in vitro has various applications in germplasm storage, industrial scale production of vegetatively propagated plants, plant biology research, and genetic transformations. One of the problems with in vitro cultivation is that plants are exposed to nonnatural conditions, such as synthetic cultivation media, low irradiance, low CO2 concentration during light periods, or high air humidity These factors can lead to an imbalance in the plants physiological equilibria and stress (Benson and RoubelakisAngelakis, 1994; Cassells and Curry, 2001). Several studies have shown that bacterial endophytes are common in plant tissues grown in vitro and that their beneficial effects on plant growth indicate that they may be useful as growth-promoting agents. The drought stress reducing activity of endophytic Bacillus and Pseudomonas spp. strains was demonstrated in grapevine plants grown in vitro (Salomon et al, 2014). In this study, we assessed the effect of seven endophytic bacteria strains of Bacillus and Pseudomonas spp. on apple shoot biomass and auxiliary shoot propagation in vitro. A proteomic analysis was employed to reveal differences in the expression of proteins participating in the apple cell response to bacterization with Bacillus spp. strains, each of which had a unique effect on the cellular redox balance and shoot development in vitro
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
