Exploring the Flowering Patterns and Control Mechanisms of Hops in Warm Climates

Jenn Hoskins
11th May, 2024

Exploring the Flowering Patterns and Control Mechanisms of Hops in Warm Climates

Image Source: Natural Science News, 2024

Key Findings

  • In Brazil, hops can flower multiple times a year without a cold period, challenging traditional growth beliefs
  • The study identified molecular changes indicating when hops transition from juvenile to adult, ready to flower
  • Key genes related to flowering in hops were more active at certain plant growth stages, even without cold weather
Understanding the flowering patterns of plants is crucial for agriculture, particularly in the face of climate change. New research from the Federal University of Lavras in Brazil has made a significant discovery about the hop plant, traditionally grown in temperate climates due to its need for a cold period, or vernalization, to flower[1]. This study has found that hops can actually flower multiple times a year in a subtropical climate, a finding that could revolutionize the hop-growing industry. Hops are a key ingredient in beer production, and their flowering time is vital for harvest and quality. In temperate regions, hop plants typically flower once a year. However, the researchers observed that in Minas Gerais, Brazil, hops grow and flower throughout the year, regardless of the season. This defies previous beliefs that hops require long daylight hours and a cold period before they can flower. The study noted that when hop plants reached between 7 and 9 nodes, the leaves transitioned from heart-shaped to trilobed, indicating a juvenile to adult phase. This was accompanied by changes in molecular pathways. Specifically, miR156, a molecule known to regulate plant development, showed the highest expression at the 5th node, while miR172s, which are associated with the transition from juvenile to adult phase, increased at the 20th node. This suggests that these molecules could be indicators of the plant's readiness to flower. Flowering in hops was observed later, around the 25th or 28th nodes. The study discovered that two genes, HlFT3 and HlFT5, were upregulated, or more active, in plants between 15 and 20 nodes. These genes are homologous to the Arabidopsis gene FLOWERING LOCUS T (FT), which is a major player in the regulation of flowering[2][3]. In Arabidopsis, FT expression in the leaf vasculature is a key factor in initiating flowering. Similarly, the hop genes HlFT3 and HlFT5 may serve a comparable role in promoting flowering in hops. Moreover, the study found that the expression of HlTFL3 was upregulated in plants with 20 nodes. HlTFL3 is analogous to the Arabidopsis gene TERMINAL FLOWER1 (TFL1), which represses flowering[3]. However, the upregulation of HlTFL3 did not appear to inhibit flowering in the subtropical conditions, which suggests that other factors may override its repressive effects. These findings are significant because they indicate that the florigenic signal, the molecular trigger for flowering, must be maintained until the hop plants are ready to bloom. In other words, the plants must reach a certain developmental stage, in terms of node number, before they can flower. This could explain the multiple flowering events observed in the subtropical climate. The research team's work builds on earlier studies that have explored the molecular pathways that control flowering in plants. For example, the interplay between light and the circadian rhythm in regulating the expression of CO and FT is well-established in Arabidopsis, where CO activates FT under long-day conditions to promote flowering[4]. This study extends our understanding of these mechanisms to hops, showing that even in the absence of a vernalization period, hops can flower under the right conditions. In conclusion, the study from the Federal University of Lavras provides new insights into the molecular mechanisms of hop flowering. It suggests that the traditional requirement for a cold period may not be as rigid as once thought, and that hops in subtropical climates can flower multiple times a year. This opens up the possibility of expanding hop cultivation to new regions, which could have significant implications for the brewing industry and agriculture in general. The findings also highlight the importance of understanding plant developmental pathways, which can lead to more resilient and adaptable crop production strategies in a changing global climate.

AgricultureGeneticsPlant Science

References

Main Study

1) Unveiling the phenology and associated floral regulatory pathways of Humulus lupulus L. in subtropical conditions.

Published 10th May, 2024

https://doi.org/10.1007/s00425-024-04428-9

Related Studies

2) cis-Regulatory elements and chromatin state coordinately control temporal and spatial expression of FLOWERING LOCUS T in Arabidopsis.

https://doi.org/10.1105/tpc.110.074682

3) A divergent external loop confers antagonistic activity on floral regulators FT and TFL1.

Journal: The EMBO journal, Issue: Vol 25, Issue 3, Feb 2006

4) The balance between CONSTANS and TEMPRANILLO activities determines FT expression to trigger flowering.

https://doi.org/10.1016/j.cub.2008.07.075


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