中文摘要：

短日照是苜蓿秋眠性的主要影响因子,故苜蓿秋眠被认为是一种光周期反应。光敏色素是光周期反应的主要受体,因而探究光敏色素与苜蓿秋眠性之间的关系可能是揭示苜蓿秋眠性机理的有效途径之一。紫花苜蓿光敏色素A、B基因尚未被克隆,本研究采用2种不同的试验策略,分别以mRNA和基因组DNA为起点,根据比较基因组学原理和生物信息学方法,利用RACE和染色体步移等手段,克隆得到了紫花苜蓿光敏色素A全长和光敏色素B近全长基因序列,为进一步探讨两者在苜蓿生长发育,特别是苜蓿秋眠性的光周期调控机制中的作用奠定了基础,并为克隆紫花苜蓿其他未知基因等研究提供思路和参考。

英文摘要：

Short days are the main environmental factor leading to fall dormancy（FD） in alfalfa（Medicago sativa） which is considered to be a photoperiodic response with phytochromes as the main receptors.This study explored efficient methods for cloning phytochromes of M.sativa,including phytochrome A（PHYA） and phytochrome B（PHYB）,which are the main phytochromes and have not been cloned in this species.Based on principles of comparative genomics and a bioinformatics approach,PHYA and PHYB genes were cloned by two different experimental strategies： using mRNA at the beginning and then the RACE technique,or by genomic DNA then genome walking.The sequences will be fundamental to studies of the relationship between FD in alfalfa and photoperiod.We also found thatM.truncatula could be used as a model plant in cloning unknown genes of M.sativa.