紫花苜蓿秋眠性对低温驯化过程与越冬耐寒适应的作用机理

紫花苜蓿(Medicago sativa)是全球性的栽培牧草, 因其秋眠性强弱而导致的抗寒性差异为深刻解析植物耐寒适应的进化生态学机制提供了一个很好的研究模式。作为多年生豆科植物, 秋眠性是紫花苜蓿适应晚秋日照缩短、温度降低, 以及提高越冬存活率的一种生长特性。秋眠性的形成与几千年来紫花苜蓿在全球的传播扩展和栽培利用有关, 长期处于不同的气候生境, 导致秋眠性的适应进化, 这为人类利用提供了丰富的遗传资源。根据秋眠性的强弱, 学术界目前将之分为11个等级。一般而言, 秋眠性的强弱影响了紫花苜蓿的低温驯化与越冬耐寒适应等过程, 导致不同品种间的抗寒性存在差异。迄今, 关于秋眠性的光温调控, 以及秋眠性影响低温驯化的生理生态过程研究较多, 而对相关的细胞信号转导与基因表达调控途径, 尤其是对秋眠性如何影响越冬紫花苜蓿抗冻蛋白作用等耐寒适应的分子机制, 尚知之甚少。针对目前研究中存在的问题, 该文提出了未来需要重点关注的科学问题。

Mechanisms underlying the effects of fall dormancy on the cold acclimation and winter hard- iness of Medicago sativa

As a global planting forage legume, alfalfa (Medicago sativa) is a valuable material to study the evolutionary and ecological mechanisms on plant adaptation to freezing due to their contrasting winter hardiness induced by fall dormancy (FD). This paper reveals that FD is an important growth characteristic that is adaptative to short-day and reducing temperature in late autumn, followed by a higher overwintering rate. Alfalfa cultivars are grouped into 11 FD ratings (numbered from 1 to 11), and this phenomenon is related to the extensive spread and cultivation for thousands of years in the globe. Alfalfa cultivars are under different climate habitats for a long time, leading to FD adaptive evolution, which provides rich genetic resources for human. In general, adaptative process associated with cold acclimation and winter hardiness in alfalfa is affected by FD, thus differences in winter hardiness exist among alfalfa cultivars. So far, regulation of FD by light and temperature and effects of FD on physiological and ecological processes involved in cold acclimation have been reported largely. However, signal transduction and the regulatory network associated with gene expression, especially the molecular mechanisms by which antifreeze proteins function in cold adaptation, are still poorly understood. Several scientific problems that need to be addressed in the future studies are highlighted in this review.