Vernalization and Floral Transition in Autumn Drive Winter Annual Life History in Oilseed Rape

First author: Carmel M. O’Neill; Affiliations: John Innes Centre (约翰英纳斯中心): Norwich, UK

Corresponding author: Steven Penfield

Plants with winter annual life history germinate in summer or autumn and require a period of prolonged winter cold to initiate flowering, known as vernalization. In the Brassicaceae, the requirement for vernalization is conferred by high expression of orthologs of the FLOWERING LOCUS C (FLC) gene, the expression of which is known to be silenced by prolonged exposure to winter-like temperatures. Based on a wealth of vernalization experiments, typically carried out in the range of 5°C–10°C, we would expect field environments during winter to induce flowering in crops with winter annual life history. Here, we show that, in the case of winter oilseed rape, expression of multiple FLC orthologs declines not during winter but predominantly during October when the average air temperature is 10°C–15°C. We further demonstrate that plants proceed through the floral transition in early November and overwinter as inflorescence meristems, which complete floral development in spring. To validate the importance of pre-winter temperatures in flowering time control, we artificially simulated climate warming in field trial plots in October. We found that increasing the temperature by 5°C in October results in raised FLC expression and delays the floral transition by 3 weeks but only has a mild effect on flowering date the following spring. Our work shows that winter annuals overwinter as a floral bud in a manner that resembles perennials and highlights the importance of studying signaling events in the field for understanding how plants transition to flowering under real environmental conditions.

经历冬季生活史的植物在夏天或秋天发芽，通常需要一段较长时间的冬季低温来起始开花，该过程叫做春化。在十字花科植物中，春化作用主要作用于平时高表达的FLC基因，该基因的表达在经历过长时间的低温后会被沉默。基于大量的春化实验（5-10°C），通常冬季的田间试验会诱导具有冬季一年生历史的农作物开花。本文中，作者发现冬季油菜中，多个FLC基因的同源基因表达量的降低并不是发生在冬季，而是发生在平均温度10-15°C的十月份。作者进一步的研究显示植物在十一月早期经历了成花转变，并以花序分生组织的形式越冬，在春天完成成花发育。为了验证冬季前温度对于开花时间调控的重要性，作者在10月的田间试验中人工模拟了气候变暖。作者发现十月份的温度平均增加5°C会导致FLC基因表达量的升高，并且将成花转变的时间往后延迟3周，但对于来年春天开花时间却影响不大。本文的研究揭示了一年生冬季植物通过一个类似于多年生植物方式，通过花芽越冬，并突出了研究田间信号事件对于深入了解植物在真实环境下如何过渡到开花的重要性。

通讯：Steven Penfield (https://www.jic.ac.uk/people/steven-penfield/)

研究方向：天气和气候如何影响植物的生殖发育和种子质量。

doi: https://doi.org/10.1016/j.cub.2019.10.051

Journal: Current Biology

Published date: December 05, 2019