How Oilseed Rape Plants Develop Differently Before Flowering in Cold vs Warm Seasons

Phil Stevens
13th February, 2024

How Oilseed Rape Plants Develop Differently Before Flowering in Cold vs Warm Seasons

Rapeseed (Brassica napus)

Photo adapted from: Daniel Cahen / CC BY (Source)
Oilseed rape, also known as canola, is a major source of vegetable oil globally, with both spring and winter types cultivated. Winter varieties require a period of cold temperatures – a process called vernalisation – to trigger flowering, while spring varieties flower independently of cold. Understanding the genetic mechanisms controlling this difference is crucial, particularly as climate change leads to milder winters, potentially disrupting the flowering of winter oilseed rape and impacting yields. Researchers at the John Innes Centre[1] have recently investigated the genetic differences between spring and winter oilseed rape varieties to better understand how vernalisation works at a molecular level. The study focused on comparing the ‘transcriptomes’ – essentially, the complete set of RNA transcripts, or gene activity – in the growing tip (apex) and leaves of a spring variety (Westar) and a winter variety (Tapidor). Samples were taken before, during, and after a cold treatment designed to mimic winter conditions, and continuing until the plants flowered. This allowed researchers to observe how gene activity changed in response to cold and developmental stage in both types of oilseed rape. A key finding was that the transcriptome in the apex tissue primarily reflected the plant’s developmental stage – how far along it was in its growth cycle. In contrast, the leaf transcriptome was more closely linked to the plant’s age. This suggests that the apex is where the key genetic programs controlling flowering are actively regulated, while the leaves respond more generally to the plant’s overall growth. Both varieties showed significant changes in gene activity during the cold treatment, driven by both temperature and changes in day length. The researchers found that while both varieties expressed similar numbers of genes overall, the timing of gene activity differed, particularly for genes known to be involved in flowering. Specifically, genes from the FLC family – known to repress flowering – were identified as playing a critical role in the differing vernalisation requirements of the two varieties. The study pinpointed copies of BnaFLC on chromosomes A2 and A10 as strong candidates for the increased cold requirement of the winter variety, Tapidor. Interestingly, other BnaFLC copies showed different patterns of activity in the apex and leaves, with some appearing to reactivate after the cold treatment, suggesting they may have evolved to respond to seasonal changes over multiple years – a characteristic of perennial plants. This finding builds on earlier work demonstrating the importance of vernalisation in a wide range of plants, including wheat and Arabidopsis[2]. Vernalisation isn’t simply about exposure to cold; it involves complex genetic networks and epigenetic changes – modifications to DNA that affect gene activity without altering the DNA sequence itself[2]. The study highlights the role of both phosphorylation and O-GlcNAcylation – chemical modifications of proteins – in regulating the VRN1 gene, a key component of the vernalisation pathway in wheat[2]. Furthermore, the study examined BnaSOC1 genes, also involved in flowering, and found evidence that different copies of this gene may have specialized functions in different tissues – a phenomenon known as ‘subfunctionalisation’. This adds another layer of complexity to understanding how flowering time is regulated in oilseed rape. The research ties into broader understanding of how plants respond to seasonal changes[3]. Plants use cues like day length and temperature to initiate developmental programs, ensuring flowering occurs at the optimal time of year. The genetic mechanisms underlying these responses have been extensively studied in model plants like Arabidopsis, and are now being unravelled in important crops like oilseed rape[3]. Understanding these mechanisms is vital for predicting how crops will respond to changing climates. The findings from the John Innes Centre have implications for breeding oilseed rape varieties that are more resilient to climate change. By identifying the specific genes and regulatory mechanisms controlling vernalisation, breeders can potentially develop varieties with more consistent and robust flowering responses, even in warmer winters. This is particularly important given the observed link between early winter temperatures and oilseed rape yields in the UK[4], where warmer winters can lead to reduced yields. As highlighted in earlier research, accurately assessing plant performance and genetic variability under changing environmental conditions is crucial for successful breeding programs[5].

AgricultureGeneticsPlant Science

References

Main Study

1) A transcriptomic time-series reveals differing trajectories during pre-floral development in the apex and leaf in winter and spring varieties of Brassica napus.

Published 12th February, 2024

https://doi.org/10.1038/s41598-024-53526-x

Related Studies

2) Remembering winter through vernalisation.

https://doi.org/10.1038/s41477-018-0301-z

3) The genetic basis of flowering responses to seasonal cues.

https://doi.org/10.1038/nrg3291

4) Yield instability of winter oilseed rape modulated by early winter temperature.

https://doi.org/10.1038/s41598-019-43461-7

5) Plant response to environmental conditions: assessing potential production, water demand, and negative effects of water deficit.

https://doi.org/10.3389/fphys.2013.00017


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