## 2 Results and Discussion
### Secoriridoids-Related Biosynthetic Genes Expression Profiles in Response to Wounding
Abbreviations: LL--local leaves, SL--systemic leaves. The intensive elicitation of the plant specialized biosynthetic pathway genes by JA exogenous treatment was well documented and recognized, but the degree to which metabolic pathways are stimulated is species-specific [61]. Moreover, distinct biosynthetic pathways respond differently to JA treatment. Thus, the MVA pathway genes in C. roseus are not induced by BIS1 overexpression or by JA treatment, while some other genes are [30]. In _Medicago truncatula_ overexpression of two bHLH jasmonate-inducible TF genes (_TSAR1_ and _TSAR2_) activated all of the genes of the MVA (mevalonate) pathway, but did not affect sterol biosynthetic genes. The overexpression of _TSAR1_ mainly enhanced nonhemolytic soya saponin biosynthesis, while the overexpression of _TSAR2_ specifically increased hemolytic saponin biosynthesis [62]. [PERSON] et al. [61] indicated that the application of methyl jasmonate (MeJA) significantly increases geniopicroside (GP) biosynthesis by up-regulating the expression of genes related to the IPP (isopentenyl pyrophosphate) pathway in _Gentiana macrophulla_, but not to the secoriidoid biosynthesis pathway. The same authors confirmed that some of these genes were up-regulated (_8 HGO_ and _GES_), while two putative encoding genes for G8O have shown different expression patterns: _G10H1_ was up-, and _G10H2_ was down-regulated [61]. Similarly, MeJA treatment also increased the transcription of _GSO_ in the seedlings of _Swertia mussotii_ and it was followed by an increase in the swertiamarin content [63]. The expression of _G8O_ has been previously described to be sufficient to increase MIA accumulation in _C. roseus_ hairy roots [64]. In our previous study on _C. erythraea_, the application of MeJA for 5 and 10 days induced the accumulation of **2** (loganin), **5** (swertiamarin), and **6** (geniopicrin), while no significant difference between non-treated and MeJA-treated plants in the amount of **4** (sweroside) and **3** (secologanin) was recorded [4]. Simultaneously, the elevated expression for several SGs biosynthetic genes (_Ce@HGO_, _Ce7 DLH2_, _Ce1O_, _Ce5 LS_, _Ce6 SO_, _Ce7 DLGT_) was noted five days after MeJA treatment [4]. Within the present research, changes in iridoids content were monitored during four days following the wounding, and it was noted that wounding leads to the noticeable changes in all of the targeted compounds except **2**. Significantly elevated levels of all genes (with the exception of _CeGPPS_) were also detected 24/48 HAW, showing the tendency of slight decrease after 96 h. It would be interesting to perform and analyze simultaneous wounding- and MeJA-elicitation responses at the level of SGs biosynthetic pathway genes expression and MeJA-responsive TFs to obtain a clearer picture of the involvement of JA signaling network in the regulation of this particular biosynthetic pathway, and that is the course of our further work. Hierarchical cluster analysis (HCA) was conducted in order to obtain a better insight regarding the linkage among biosynthetic genes and TFs involved in wounding response in _C. erythraea_ leaves. Two separated clusters are noticeable based on the presented tree (Figure 4). The first cluster (A) contains majority of TFs (_CeJAM2_, _CeJAM3_, _CeJAZ1_, and _CeMYC2_), and _CeGPPS_ biosynthetic gene. This cluster is separated in two sub-clusters, with the first one (a1) being formed of _CeMYC2_, while other TFs and _CeGPPS_ are grouped within the second sub-cluster (a2). All of the other SGs biosynthetic genes and two TFs (_CeBIS1_ and _CeCO11_) are grouped within cluster B and they are also separated into two sub-clusters. The first sub-cluster (b1) is formed of seven biosynthetic genes (_CeGES_, _CeG8O_, _Ce8 HGO_, _CeIS_, _CeIO_, _Ce7 DLGT_, and _Ce7 DLH_), where _Ce7 DLGT_ is visibly distinguished from the others. On the other hand, _CeSLS_ and _CeBIS1_, which displayed similar expression patterns in response to wounding, grouped closely in HCA within the sub-cluster (b2), together with _CeCO11_.