## 2 Results
### Expression Profile of Genes of Ascorbate Biosynthesis under Biotic Stresses  
To obtain an overview of the expression profile of genes involved in pepper Asc biosynthesis that succumbed to pathogenic infections, data from two transcriptomic experiments were analyzed. Investigation into leaf transcriptome of two bell pepper near-isogenic lines (NIL), one infected with bell pepper endornavirus (BPEV+) and other BPEV-free, was conducted, and both were further inoculated with pepper mild motile virus (PMMoV) resulting in the following treatments: BPEV\(-\)/Mock, BPEV+/Mock, BPEV\(-\)/PMMoV, and BPEV+/PMMoV (PRJNA588750; Table S2) [41]. The studied genes from the L-galactose pathway were apparently more responsive to PMMoV and BPEV+/PMMoV infections with some interesting peculiarities (Figure 9 and Table S9). In all treatments, _PMM_ and _GGP1_ mRNA increased, while _GMP1_, _GGP2_, and _GalLDH_ decreased their levels, mainly in leaves infected with BPEV+/PMMoV. However, _GalDH_ and remarkably _GME1_ were up-regulated,  
Figure 8: Heatmap illustration of genes encoding ascorbate biosynthesis pathways in leaves of two pepper genotypes, a susceptible (‘ZHC1’) and another tolerant (‘ZHC2’) to waterlogging at 6 h and 24 h of waterlogging stress, and 1 h post recovery (PRJNA793609). Up\(-\) and down\(-\)regulated genes are indicated in red and green colors, respectively, according to \(Z-\)score values obtained from three biological replicates. Statistical significance is shown in Table S8.  
whilst _GME2_ and _GPP1_ and \(2\) transcripts reduced only in PMMoV and BPEV+/PMMoV, mostly in the last one. Interestingly, genes from the L-gulose pathway _GULO1_ and \(2\) and _GULUR_ (D-galacturonate) were up-regulated in BPEV+/PMMoV compared to BPEV+, indicating some contribution to Asc biosynthesis process, while _MIOX3_ transcripts were augmented only in BPEV+.  
Figure 9: Heatmap illustration of genes encoding enzymes of ascorbate biosynthesis pathways in leaves of two bell pepper near-isogenic lines (NIL), one infected with bell pepper endor-navirus (BPEV+) and other with BPEV-free, and both further inoculated with PMMoV as follows: BPEV\(-\)/Mock, BPEV+/Mock, BPEV\(-\)/PMMoV, and BPEV+/PMMoV (PRJNA588750). Up\(-\) and down\(-\)regulated genes are indicated in red and green colors, respectively, according to \(Z-\)score values obtained from two biological replicates. Statistical significance is shown in Table S9.  
Subsequently, genes of ascorbate biosynthesis pathways revealed specific strain responses to apical stems infected with three tobacco etch virus (TEV) strains (HAT, Mex21, and N) at 7 and 14 days post-inoculation (dpi) (PRJNA476480) [42]. The infection caused by severe N strain, negatively affected the expression of genes from L-galactose, myo-inositol, and L-glucose pathways, mainly at 14 dpi (Figure 10 and Table S10). Among them, _GMP1_, _GME1_ and 2, _GPP1_, _GalLDH_, and _GalLDH_, and notably _MIOX3_ (myo-inositol pathway) experienced a decrease in their mRNA amounts at 7 dpi. Remarkably, almost all genes from L-galactose, _MIOX1_ and _3, _GulLO1_, and _GalUR_ from alternative pathways were down-regulated at 14 dpi in the N strain, whereas HAT and Mex21 did not alter gene expression at 7 dpi, while transcript amounts of _PMI3_, _GMP1_, _GME1_ and 2, _GGP2_, _GPP1_, _GalDH_, _GalLDH_, and _GulLO1_ were sharply reduced by Mex21 inoculation at 14 dpi.  
Figure 10: Heatmap illustration of genes encoding enzymes of ascorbate biosynthesis pathways in apical steams infected with three tobacco etch virus (TEV) strains (HAT, Mex21, and N) at 7 and 14 days post-inoculation (dpi) (PRJNA476480). Up\(-\) and down\(-\)regulated genes are indicated in red and green colors, respectively, according to \(Z-\)score values obtained from two biological replicates. Statistical significance is shown in Table S10.