Unlocking the Secret Flavor Makers: The Surprising Role of HlMYB7 in Hop Brewing

TLDR; Important concepts:

• Hops contain valuable compounds that contribute to the aroma and flavor of beer

• This includes prenylflavonoids (PF) and bitter acids (BA)

• HlMYB7 is a transcription factor that regulates the biosynthesis of PF and BA

• The HlMYB7 transcription factor represses the biosynthetic pathway for these compounds in hop

• Constitutive expression of HlMYB7 leads to stunted growth, delayed flowering, and reduced tolerance to viroid infection in hop.

• HlMYB7 also stops the protein complexes from regulating BA and PF production

• HlMYB7 could be a target for metabolic engineering in the brewing industry

WHY IS IT IMPORTANT:

This research is important because it explains how the hop plant produces compounds like flavonoids, bitter acids, and essential oils that are very valuable for the brewing industry.

The researchers studied a specific gene called HlMYB7, which controls the production of two important compounds in hops, prenylflavonoids (PF) and bitter acids (BA). They found that when HlMYB7 is over-expressed, it can cause the hop plant to grow poorly and become more vulnerable to certain diseases.

They also found that HlMYB7 can suppress the production of PF and BA by targeting specific genes and protein complexes.

The results of this study could be useful for scientists who want to develop new ways to control the production of these valuable compounds in hops through genetic engineering.

Review: The multifaceted roles of R2R3 transcription factor HlMYB7 in the regulation of flavonoid and bitter acids biosynthesis, development and biotic stress tolerance in hop (Humulus lupulus L.)

The article discusses how hops, a plant used in the brewing industry, creates valuable compounds such as flavonoids, bitter acids, polyphenols, and essential oils, and how these compounds are regulated at a transcriptional level. The study focuses on the regulatory functions of a specific transcription factor called HlMYB7 in controlling the biosynthesis of two important secondary metabolites, prenylflavonoids (PF) and bitter acids (BA), which are responsible in part for the aroma and flavor of beer.

Definition: Prenylflavonoids (PF) and bitter acids (BA) are secondary metabolites produced by the hop plant (Humulus lupulus), which are responsible for the bittering flavor, floral aroma, and preservative activity in beer. Prenylflavonoids are a type of flavonoid compound that have a prenyl group attached, while bitter acids are a type of organic acid that are responsible for the bitterness in beer. They are found in the lupulin gland.

The researchers found that HlMYB7 suppresses the transcription of structural genes involved in the terminal steps of biosynthesis of PF and BA, leading to reduced accumulation of these compounds. They also discovered that HlMYB7 targets both PF and BA pathway genes and suppresses protein complexes involved in regulating these pathways.

Furthermore, when HlMYB7 is expressed in other plants such as Arabidopsis thaliana, it downregulates structural genes of flavonoid pathway, resulting in a decrease in anthocyanin content in Nicotiana tabacum. This suggests that HlMYB7 plays a crucial role in balancing the accumulation of secondary metabolites in plants.

The study highlights the importance of HlMYB7 in regulating the biosynthesis of valuable compounds in hops and suggests that it could be a target for metabolic engineering in the brewing industry.

Ajay Kumar Mishra, et.al; The multifaceted roles of R2R3 transcription factor HlMYB7 in the regulation of flavonoid and bitter acids biosynthesis, development and biotic stress tolerance in hop (Humulus lupulus L.), Plant Physiology and Biochemistry, 2023,ISSN 0981-9428, https://doi.org/10.1016/j.plaphy.2023.03.013.