Figure 1.
Short term effects of different inocula of Burkholderia phytofirmans PsJN in Arabidopsis thaliana plantlets.
Different measurements in plants at 14 DAS treated with several bacterial inocula. A) Plant fresh weight, B) Dry weight, C) Root hairs and D) Chlorophyll content. Media and standard errors (SE) are the result of at least 40 plants per treatment and results are representative of three independent experiments. Same letters indicate non-significant differences among treatments (One way ANOVA, p<0.05).
Figure 2.
Effects of Burkholderia phytofirmans PsJN on Arabidopsis thaliana roots.
A) In vitro growth of primary roots under different treatments. Media and SE are the result of at least 30 plants per treatment and results are representative of three independent experiments. Same letters indicate non-significant differences among treatments (One way ANOVA, p<0.05). B) Representative photographs of root hairs formed at the primary root tip region of 8 DAS Arabidopsis seedlings grown in indicated treatments. K-PsJN represents the killed bacteria treatment. C) Representative photograph of epifluorescence images of root colonization of A. thaliana plants by strain PsJN::GFP; bacterial cells are observed as colonies attached to the surface of the root (arrow), bar represents 200 μm. D) Confocal microscope image of a root colonization by strain PsJN::GFP at the root tip, bar represents 10 µm. E) Confocal microscope of a root colonized endophytically by PsJN :: GFP (roots were washed with ethanol and sterile water before being observed under microscope); cells are observed as colony attached to lateral root emergence and in an intercellular position, between the epidermal layer, bar represents 30 µm.
Figure 3.
Gene ontology of biological processes affected in Arabidopsis thaliana plants treated with Burkholderia phytofirmans PsJN and K-PsJN.
The figure shows the number of genes induced or repressed in plants treated by strain PsJN (A) or K-PsJN (B) in comparison to control conditions and its distribution within the different Gene Ontology biological functions. Only those genes with differential expression (p<0.05) were plotted, corresponding to 159 and 249 genes up-regulated and down-regulated, respectively in PsJN treatment. With the K-PsJN treatment 364 genes were up-regulated and 282 were down-regulated. Each gene could be assigned to more than one category. The VirtualPlant platform [50] was utilized in order to determine which GO terms were statistically overrepresented compared with the GO term represented into the Arabidopsis genome arrays (asterisks, p<0.01).
Figure 4.
Quantitative real time PCR of selected up and down-regulated genes after inoculation of Arabidopsis with Burkholderia phytofirmans PsJN.
Quantitative RT-PCR determinations of relative levels of gene expression in complete plants at 2 first leaves emerging (EL), 2 leaves expanded (2L), 4 rosette leaves (4L) or 6 rosette leaves (6L) stages. Graphics in the left side of the figure correspond to those genes that were up-regulated at 4L stage under PsJN treatment (the stage were affymetrix analyzes were performed) and in the right are those genes with down-regulation at 4L stage. Data are means ± SE. Asterisk indicates statistical significance (One way ANOVA, p<0.05).
Figure 5.
Effects of Burkholderia phytofirmans PsJN on aerial zone during long-term growth of Arabidopsis thaliana plants.
A) Representative photographs of A. thaliana rosettes of plants exposed to the different treatments (K-PsJN represents the killed bacteria treatment) at 18 DAS, bars correspond to 0.5 cm. B–D) Graphic representation of rosette media areas (B) average rosette leaf number per plant (C) and average rosette leaf areas (D) of plants subjected to the different treatments. Media and SE were calculated with at least 12 plants per treatment, and results are representative of three independent experiments. Asterisks indicate significant differences among PsJN treatment and the two other treatments in each time (One or two-way ANOVA, p<0.05). E) Representative photographs of the adaxial surface of third rosette leaves from 40 DAS plants. Bars represent 100 µm.
Figure 6.
Effects of Burkholderia phytofirmans PsJN on flowering and senescence of Arabidopsis thaliana plants.
A) Percentage of plants presenting floral primordia in the different treatments. B) Number of senescent leaves in plants of the different treatments at different days after sowing. Asterisks represent significant differences (One way ANOVA, p<0.05). Media and SE represent measurements of at least 12 plants per treatments and results are representative of three independent experiments.
Figure 7.
Expression of flowering key regulator genes after inoculation of Arabidopsis with Burkholderia phytofirmans PsJN.
Quantitative RT-PCR determinations of relative levels of expression of LEAFY and AP1 (APETALA1) genes in complete plants at 6 rosette leaves stage. Data are means ± SE. Asterisk indicates statistical significance (One way ANOVA, p<0.05).