A photoreceptor molecule in plant cells has been found to have a second job as a thermometer after dark – allowing plants to read seasonal temperature changes. Scientists say the discovery could help breed crops that are more resilient to the temperatures expected to result from climate change

植物细胞中的一种光感受器分子被发现具有第二种功能——在黑暗环境下充当温度计，使植物能够感知季节性的温度变化。科学家表示，这一发现可能有助于培育更能适应气候变化带来的预期温度变化的作物。

A. 由剑桥大学领导的国际科学家团队发现，植物中的“温度计”分子使它们能够根据季节性温度变化进行发育。研究人员揭示，被称为光敏色素的分子——植物在白天用来检测光线——在黑暗中实际上会改变其功能，成为测量夜间热度的细胞温度计。

A An international team of scientists led by the University of Cambridge has discovered that the 'thermometer' molecule in plants enables them to develop according to seasonal temperature changes. Researchers have revealed that molecules called phytochromes – used by plants to detect light during the day – actually change their function in darkness to become cellular temperature gauges that measure the heat of the night.

发表在《科学》杂志上的新发现表明，光敏色素控制着基因对温度和光的反应，来决定植物的生长。

B. 科学家把光敏色素比作温度计中的水银。他们表示，这些分子会在夜间改变状态，而且它们的变化速度与温度成正比。温度越高，分子变化的速度就越快--这会刺激植物的生长。

The new findings, published in the journal Science, show that phytochromes control genetic switches in response to temperature as well as light to dictate plant development.

C.几百年前，农民和园丁就已经知道植物对温度的反应:温暖的冬天会导致许多树木和花朵提早发芽这是人类长期以来用来预测下一年的天气和收获时间的方法。最新的研究首次确定了植物中对温度有反应的分子机制--通常引发我们渴望在冬天结束时看到的春芽。

D.因为气候变化，天气和温度变得越来越不可预测。研究人员表示，这种感光分子也可以作为植物细胞内的温度计，这一发现有助于帮助我们培育更坚韧的作物。“据估计，到2050年，农业产量需要翻一番，但气候变化是实现这一目标的主要威胁。例如小麦和水稻等关键作物对高温很敏感。温度每升高一度，热应力就会使作物减产10%左右。“剑桥大学赛恩斯伯里实验室的首席研究员 Dr Philip Wigge 说，“发现允许植物感知温度的分子，有可能加快对适应热应激和气候变化的作物的培育。

B At night, these molecules change states, and the pace at which they change is 'directly proportional to temperature', say scientists, who compare phytochromes to mercury in a thermometer. The warmer it is, the faster the molecular change – stimulating plant growth.

E. 当光敏素分子处于活跃状态时，它们与DNA结合以限制植物生长。在白天，阳光激活了这种分子，减缓生长。如果植物发现自己处于阴凉处，光敏色素就会快速灭活--确保其快速生长，并再次找到阳光。这就是植物为了躲避彼此的阴影而相互竞争的方式。“光驱动的光敏色素活性变化发生地非常快不到一秒即可完成。“Wigge说。

然而，到了夜晚，情况就不同了。分子不再迅速地失活，而是逐渐地从活跃状态变为不活跃状态。这被称为“暗逆转”。Wigge说:“就像温度计里的水银上升一样，光敏色素在夜间回复不活跃状态的速率，就是温度的直接测量标准。“

C Farmers and gardeners have known for hundreds of years how responsive plants are to temperature: warm winters cause many trees and flowers to bud early, something humans have long used to predict weather and harvest times for the coming year. The latest research pinpoints for the first time a molecular mechanism in plants that reacts to temperature – often triggering the buds of spring we long to see at the end of winter.

F. 温度越低，光敏色素恢复到不活跃状态的速度就越慢，因此分子会在活跃的、抑制生长的状态中维持的时间更长。这就是植物在冬天生长缓慢的原因。温暖的温度会加速黑暗逆转，因此光敏色素可以快速回到不活跃的状态，并从植物的DNA中分离出来使得基因得以呈现，植物得以恢复生长。“Wigge认为光敏色素热感测是在较晚的阶段进化出来的，并增补了生物网络。这种生物网络已经用于夜间间歇期基于光的生长。

G.一些植物主要利用日照长度作为季节的指标。而其他植物，例如水仙花，对温度相当敏感，并且可以在温暖的冬天提前几个月开花。事实上，光敏色素的双重作用的发现为一段著名的歌谣提供了科学依据，这段歌谣长时间被用于预测即将到来的季节橡树先于白蜡，我们会被淋湿;白蜡先于橡树，我们会被浸泡。

D With weather and temperatures set to become ever more unpredictable due to climate change, researchers say the discovery that this light-sensing molecule also functions as the internal thermometer in plant cells could help us breed tougher crops. 'It is estimated that agricultural yields will need to double by 2050, but climate change is a major threat to achieving this. Key crops such as wheat and rice are sensitive to high temperatures. Thermal stress reduces crop yields by around 10% for every one degree increase in temperature,' says lead researcher Dr Philip Wigge from Cambridge's Sainsbury Laboratory. 'Discovering the molecules that allow plants to sense temperature has the potential to accelerate the breeding of crops resilient to thermal stress and climate change.'

Wigge 解释道:“橡树更多地依赖于温度，可能是用光敏色素作为温度计来指示生长，而白蜡树则依赖于测量白天的长度，来决定它们的季节时间。一个温暖的春天，随之而来的很可能是一个炎热的夏天，会导致橡树先于白蜡树长出叶子。而寒冷的春天则刚好相反。英国人非常清楚，一个凉爽的夏天很可能是雨水连绵的。

H. 这项新发现是来自德国、阿根廷和美国的科学家以及剑桥大学团队12年研究的成果。这项工作是在一个模型系统中完成的，使用的是一种叫作拟南芥的芥菜植物，但是Wigge说，在农作物中也发现了温度感应所必须的光敏色素基因。“植物遗传学的最新进展意味着科学家们能够快速地辨别农作物中控制这些进程的基因，甚至通过精确的分子'手术刀’来改变它们的活性。“Wigge补充道。“剑桥大学在做这类研究方面具有独特的优势，因为我们周围有杰出的伙伴，他们研究植物生物学的更多应用，并且能够帮助我们将这些新知识迁移到该领域。“

E In their active state, phytochrome molecules bind themselves to DNA to restrict plant growth. During the day, sunlight activates the molecules, slowing down growth. If a plant finds itself in shade, phytochromes are quickly inactivated – enabling it to grow faster to find sunlight again. This is how plants compete to escape each other's shade. 'Light-driven changes to phytochrome activity occur very fast, in less than a second,' says Wigge.

At night, however, it's a different story. Instead of a rapid deactivation following sundown, the molecules gradually change from their active to inactive state. This is called 'dark reversion'. 'Just as mercury rises in a thermometer, the rate at which phytochromes revert to their inactive state during the night is a direct measure of temperature,' says Wigge.

F 'The lower the temperature, the slower the rate at which phytochromes revert to inactivity, so the molecules spend more time in their active, growth-suppressing state. This is why plants are slower to grow in winter. Warm temperatures accelerate dark reversion, so that phytochromes rapidly reach an inactive state and detach themselves from the plant's DNA – allowing genes to be expressed and plant growth to resume.' Wigge believes phytochrome thermo-sensing evolved at a later stage, and co-opted the biological network already used for light-based growth during the downtime of night.

G Some plants mainly use day length as an indicator of the season. Other species, such as daffodils, have considerable temperature sensitivity, and can flower months in advance during a warm winter. In fact, the discovery of the dual role of phytochromes provides the science behind a well-known rhyme long used to predict the coming season: oak before ash we'll have a splash, ash before oak we're in for a soak.

Wigge explains: 'Oak trees rely much more on temperature, likely using phytochromes as thermometers to dictate development, whereas ash trees rely on measuring day length to determine their seasonal timing. A warmer spring, and consequently a higher likeliness of a hot summer, will result in oak leafing before ash. A cold spring will see the opposite. As the British know only too well, a colder summer is likely to be a rain-soaked one.'

H The new findings are the culmination of twelve years of research involving scientists from Germany, Argentina and the US, as well as the Cambridge team. The work was done in a model system, using a mustard plant called Arabidopsis, but Wigge says the phytochrome genes necessary for temperature sensing are found in crop plants as well. 'Recent advances in plant genetics now mean that scientists are able to rapidly identify the genes controlling these processes in crop plants, and even alter their activity using precise molecular “scalpels”,' adds Wigge. 'Cambridge is uniquely well-positioned to do this kind of research as we have outstanding collaborators nearby who work on more applied aspects of plant biology, and can help us transfer this new knowledge into the field.'