Fig. 7
Effects of exogenous GABA application on the endogenous GABA content and its transport carrier CsgabP from healthy and Huanglongbing-affected Valencia sweet orange (Citrus sinensis). (A and B) Endogenous levels of GABA after the treatment with different GABA concentrations (0, 1, 5, 10, and 50 mM) from healthy and ‘Ca. L. asiaticus’-infected Valencia sweet orange, respectively. (C and D) Simple linear regression (SLR) and second-degree polynomial regression (SPR) analyses between exogenous GABA concentration (mM) and endogenous GABA content (µg.g− 1 FW) from healthy and ‘Ca. L. asiaticus’-infected Valencia sweet orange, respectively. (E and F) Relative gene expression of CsgabP after the treatment with different GABA concentrations (0, 1, 5, 10, and 50 mM) from healthy and ‘Ca. L. asiaticus’-infected Valencia sweet orange, respectively. (G and H) SLR and SPR analyses between exogenous GABA concentration (mM) and CsgabP relative gene expression from healthy and ‘Ca. L. asiaticus’-infected Valencia sweet orange, respectively. (I and J) SLR and SPR analyses between endogenous GABA content (µg.g− 1 FW) and CsgabP relative gene expression from healthy and ‘Ca. L. asiaticus’-infected Valencia sweet orange, respectively. In panels A, B, E, and F, the data presented are the means ± standard deviation (mean ± SD) of six biological replicates (n = 6). Different letters signify statistically significant differences among treatments, whereas the same letters indicate no significant differences among them using Tukey’s HSD (p < 0.05). In SLR and SPR panels, blue dots represent raw data (n = 6). The fitted SLR line is presented as a red line, while SPR models are presented as blue lines. The 95% confidence intervals for the estimated regression are shaded with the same color and edged by dotted lines. Regression equations for both SLR and SPR models, R2and p-value based on the F test (p ≤ 0.05) were also obtained and are presented within the graphs.
