# Signaling in the Tomato Immunity against _Fusarium oxysporum_
## 2 Results
### Movione Tomato Plants Activate an Early JA-and ABA-Mediated Defense Response after Fol Infection  
To better characterize the infection in both isogenic lines, the activation of the main signaling defensive routes was studied. The expression levels of different marker genes corresponding to the pathways mediated by SA, JA, ET, or ABA, which are the most important phytohormones involved in plant defense, were analyzed by using RT-qPCR (Figure 2) both in susceptible MOM (MOM) and resistant Movione (MOV) tomato plants after 3, 7, and 14 days of _Fol_ inoculation. To avoid possible differences between the Moneymaker isogenic lines, logarithm of the ratios (log(ratio)) of the relative expression levels between _Fol_-infected and mock-inoculated plants were calculated; log(ratio) above 0 indicating a _Fol_-provoked induction of the marker gene. Figure 1: Fusarium wilt symptoms in MOM (MOM) and Movione (MOV) tomato plants at 14 dpi after _Fusarium oxysporum_ f. sp. _bycopersici_ (_Fol_) inoculation. Tomato plants display the representative phenotype observed in infected susceptible MOM (**B**) compared to mock-inoculated (**A**), and infection-resistant MOV (**D**), as compared to their corresponding mock-inoculated (**C**). The expression of _PR1_ (pathogenesis-related 1), which is the marker gene for SA-mediated plant response [18], showed a statistically significant increase in the log(ratio) of the susceptible isogenic line when compared to the resistant plants, in accordance with the symptom development (Figure 2A). Specifically, the log(ratio) of the induction of _Fol_-infected MOM plants with respect to the mock MOM plants was 1-, 1.8-, and 2.2-fold at 3 dpi, 7 dpi, and 14 dpi, respectively. In contrast, MOV plants showed a log(ratio) below 0 at 3 dpi (\(-\)1.9) and 14 dpi (\(-\)0.8), thus indicating a _Fol_-mediated downregulation of _PR1_ in this resistant isogenic line. The analysis of _JAZ7_ (asmonate ZIM-domain 7) (Figure 2B), a gene related to the JA pathway [19], showed similar results at the end of the fungal infection, while a statistically significant increase in the log(ratio) was found at 3 dpi (0.2) in the resistant MOV plants with respect to the susceptible MOM. _ACS2_ (aminocyclopropane-1-carboxylate synthase 2) expression was chosen to follow the ethylene-mediated signalling [20]. No relevant induction was found in the resistant MOV tomato plants upon fungal inoculation at any time point since the log(ratio) was negative (-0.8 at 3 dpi) or around 0 (0.1 at both 7 and 14 dpi) (Figure 2C). However, _ACS2_ was significantly induced in the _Fol_-infected MOM plants during the pathogenic interaction, displaying a log(ratio) of 1.2, 0.9, and 2.2 at 3, 7, and 14 dpi, respectively. Differences between the log(ratio) of MOM and MOV plants were observed for _LEA_ (late embryogenesis abundant) (Figure 2D), a gene related to ABA [21], with these differences being statistically significant at any time point. It should be noted that there was a significant induction of _LEA_ (0.5) at 3 dpi in the resistant MOV plants compared to the susceptible MOM. Nevertheless, a decrease in the expression pattern for these genes was found in MOV plants along the infection process. Our results suggest that the susceptible MOM plants activated all the main defense pathways along the infection, this response being late and insufficient to stop the disease progression in accordance with the symptom development. However, MOV plants were  
Figure 2: Logarithm of the ratios of the relative expression levels of _PR1_ (**A**), _JAZ7_ (**B**), _ACS2_ (**C**), and _LEA_ (**D**) between _Fol_-inoculated and mock-inoculated susceptible MOM, white) and resistant Movione (MOV, gray) tomato plants upon _Fusarium oxysporum t_. sp. _lyocypersi_ infection at 3, 7, and 14 dpi by RT-qPCR. Values obtained were normalized in relation to the elongation factor 1 \(\alpha\) (accession X53043.1). cDNA expression levels were expressed as the average log(ratio) values of a representative experiment.