## Results and Discussion
### Nematode Responsive Phytohormones and Transcription Factors  
Plant hormones are key players in mediating plant defense following nematode attack. Similarly, in this study _M. javanica_ infestation influenced the expression of several genes associated with the synthesis and signaling of JA, SA, ET, auxin, abscisic acid (ABA), and brassinosteroids (BR) (Figures 4 and 6). The salicylic acid pathway is effective against biotrophic parasites while JA and ET pathway synergy is associated with enhanced resistance against necrotrophic microbes and herbivorous insects [48]. In this study, 9 out of 12 genes associated with SA biosynthesis were up-regulated (Figure 6A). Moreover, genes encoding for PR-1 (five genes) a robust marker of SA responsive genes expression were up-regulated at 3 and/or 7 dpi (Figure 5D and Table S5), indicating activation of  
Figure 6: Heat map illustration of differentially expressed genes involved in hormone signal transduction. (**A**) Salicylic signaling pathway. (**B**) Jasmonic signaling pathway. (**C**) Ethylene signaling pathway. (The heat map illustrates a subset of genes from each group. Refer supporting information for all differentially expressed genes in each group). systemic induced resistance. Genes encoding for enzymes involved in the JA synthesis allene oxide synthase (_AOS_ 2 genes), allene oxide cyclase (_AOC_, one gene), lipoxygenase (_LOX_, four genes), and 12-oxophytodienoate (_12-OPR_, three genes) were down-regulated at both time points (Figure 6B and Table S5). Consequently, down-regulation of _LOX_ and _12-OPR_ enzymes might have played a role in initiating a susceptible interaction through interfering with JA-mediated defense pathway. The _LOX_ pathway mediates resistance against phytopathogens including nematodes [49]. Plants incapable of producing JA or 12-oxo-phytodieenoic acid (_OPDA_) are more susceptible to phytonematodes [50]. Moreover, four protease inhibitors coding genes were down-regulated in this study at 3 and 7 dpi (Figure 5D and Table S5). Jasmonic acid enhances expression of protease inhibitors which prevent proteolytic activity of the insect's enzymes to debilitate their growth and reproduction. Nematodes essentially, depend on proteases to acquire nutrients as their source of food [47]. Hence, it is likely that JA plays a role in mediating defense against _M. javancia_. The antagonistic effect of SA on the JA pathway is often expressed at the gene transcription level, where SA targets the JA signaling. For instance, _WRKY50_ plays a role in SA mediated suppression [48] was up-regulated in the current study (Figure 7C and Table S5). Furthermore, TGA, sub-class of basic leucine zipper (bZIP) family of TFs are important molecular players in mediate JA suppression through SA. In this study, two genes coding for _TGA4_ were up-regulated (Table S5) further signifying suppression of JA pathway through induction of SA signaling pathway. Taken together, we can deduce that _M. javancia_ adopts the strategy of targeting the SA pathway which concurrently suppresses JA-dependent defense responses resulting in potato susceptibility. In addition to suppression of JA defense pathway, genes involved in ET synthesis, 1-aminocyclopropane-1-carboxylate synthase, and 1-aminocyclopropane-1-carboxylate were differentially regulated in this study with 4 and 5 genes down-regulated, respectively (Figure 7C and Table S5). We also detected a gene encoding for ETHYLENE RESPONSE SENSOR 1 up-regulated (Figure 7C and Table S5) which acts as negative regulators of ET responses suggesting ET suppression. Previous research demonstrated that ET inhibits RKN infestation, probably through a decrease in nematode attraction to the roots [47]. In the same way, rice resistant plants show more up-regulation of ET biosynthesis and response genes than susceptible plants infested with RKN [14; 51]. Transcriptional reprogramming is a key hallmark of plant innate immunity.