## 2 Results
### Analyses of Gene Expressions in Hop Cones of Healthy and HVLd-Infected Plants
Therefore, we studied relative expressions of eight monoterpene and sesquiterpene biosynthetic pathway enzyme genes (Table 5). The GPPS-SSU (Figure 5A) gene, which is a part of heterodimer enzyme complex for monoterrenes precursor biosynthesis, was down-regulated by infection in cones of all the cultivars: Saaz (2.5 times), Sladek (2.8 times), Preimant (10 times), and Agnus (1.7 times). The FPPS (Figure 5B) gene, which is an enzyme for sesquiterpenrenes precursor biosynthesis, was significantly up-regulated by infection in cones of the Saaz (2.3 times) cultivar but non-significantly down-regulated by infection in cones of the Saaz (2.3 times) cultivar. The FPPS (Figure 5A) gene, which is an enzyme for sesquiterpenrenes precursor biosynthesis, was significantly up-regulated by infection in cones of the Saaz (2.3 times) cultivar but non-significantly down-regulated by infection in cones of the Saaz (2.  
in cones of the Sladek (1.8 times), Premiant (1.6 times), and Agnus (1.4 times) cultivars. Both genes MTS1 (Figure 5C) and MTS2 (Figure 5D), which are enzymes for monoterpenes biosynthesis, were down-regulated by infection in cones of all the cultivars: Saaz (2.1 and 2.1 times), Sladek (1.4 and 0.9 times), Premiant (1.6 and 2.8 times), and Agnus (1.1 and 3 times). Additionally, both genes STS1 (Figure 5E) and STS2 (Figure 5F), which are enzymes for sesquiterpenes biosynthesis, were down-regulated by infection in cones of the Saaz (5.9 and 2.3 times), Sladek (2.2 and 13.8 times), and Agnus (2 and 3.3 times) cultivars. The TPS9 (Figure 5G) gene, which is a terpene biosynthesis enzyme with an unknown substrate, was significantly up-regulated by infection in cones of the Agnus (3.1 times) cultivar. Figure 5: The relative expression to reference genes (RE = 1) for terpen biosynthesis genes (**A**) GPPS-SSU, (**B**) FPPS, (**C**) MTS1, (**D**) MTS2, (**E**) STS1, (**F**) STS2, (**G**) TPS9, and (**H**) NES in young cones of HLVd-free and infected plants of hop cultivars. Probability level: *—_p_ < 0.1, **—_p_ < 0.05, and ***—_p_ < 0.01. Note: straight line—median; dashed line—average; and box—95% percentile \(\pm\) standard deviation. Secondary metabolite biosynthesis pathways are regulated by transcription factors' network. Therefore, we studied relative expressions of six known transcription factors with influence on the transcription of biosynthetic pathway enzyme genes (Table 5). The MYB3 (Figure 6A) transcription factor was significantly down-regulated by infection in cones of the Sladek (4.4 times) and Premiant (5.9 times) cultivars. The MYB8 (Figure 6B) transcription factor was non-significantly down-regulated by infection in cones of the Saaz (1.5 times) and Sladek (16 times) cultivars. The MYB8 (Figure 6C) transcription factor was significantly down-regulated by infection in cones of the Premiant (6.5 times) cultivar. The bHLH2 (Figure 6D) transcription factor was non-significantly down-regulated by infection in cones of all the cultivars except Saaz. The bHLH4 (Figure 6E) transcription factor was significantly down-regulated by infection in cones of thhe Saaz (1.6 times) cultivar but significantly up-regulated by infection in cones of the Sladek (2.6 times) cultivar. The WRKY1 (Figure 6F) transcription factor was significantly down-regulated by infection in cones of the Sladek (1.9 times) and Premiant (2.7 times) cultivars. Considering that transcription factors are involved in the regulation of gene expression, we screened promoter sequences of biosynthetic pathway enzymes for binding sites of MYB, bHLH, and WRKY factors (Table 6). To a lesser extent, two and three cis-acting regulatory DNA elements were found for MYB and bHLH (MYC) or WRKY transcription factors, respectively, in the studied promoter sequences. Figure 6: The relative expression to reference genes (RE = 1) for biosynthesis transcription factor genes (**A**) MYB3, (**B**) MYB8, (**C**) MYB8, (**D**) bHLH2, (**E**) bHLH4, and (**F**) WRKY1 in young cones of HLVd-free and infected plants of hop cultivars.