摘要
休眠是落叶果树在遇到不良环境或季节性变化而停止分生组织活动的一种适应性现象,具有重要的生物学意义和潜在的经济价值.芽休眠的研究起步较晚,但随着果树生理学和分子生物学研究的不断深入,芽休眠的生理和遗传机制研究得到了广泛关注.桃作为蔷薇科果树的模式树种,对芽休眠的研究有着一定的代表意义.研究桃芽休眠机制,有助于人工调节休眠及选育不同需冷量的桃新品种,以应对气候变化.本文主要从桃芽休眠的影响因素、生理机制和调控桃芽休眠的MADS-box(DAM)基因等方面归纳总结了近年来有关桃芽休眠方面的研究进展,以期为深入研究桃芽休眠及相关应用提供科学依据.促进桃芽进入休眠状态的主要环境因子是短日照和低温,休眠期长短与品种需冷量高低息息相关,需冷量与萌芽开花呈正相关,即需冷量越低萌芽开花越早,需冷量越高萌芽开花越晚;控制需冷量的主效基因PpDAM6的启动子区的30-bp结构变异与需冷量表型高度相关,30-bp缺失仅存在于低需冷量品种中.长日照使休眠延迟;高温可影响芽休眠相关基因的表达量,从而促进芽休眠的解除.影响桃芽休眠的内部因素主要是植物激素脱落酸、赤霉素以及碳水化合物、蛋白、挥发性物质等代谢物.桃芽中ABA生物合成关键基因PpNCED1和PpNCED2在休眠建立时上调表达,在休眠解除时下调表达,并随着低温的积累而降低;相反,ABA降解基因PpC-YP707A2和PpCYP707A3的表达随着低温积累时间的延长呈上升趋势,这2种基因的表达与ABA含量的变化趋势相一致.GA属于萌发促进物质,被认为是调节芽休眠解除的关键激素,活性赤霉素主要有GA1、GA3、GA4.休眠期间ABA含量下降,GA含量升高,ABA/GA比值降低,休眠解除时达到最低,主要由ABA含量下降而引起.碳水化合物、蛋白、挥发性物质等代谢物在调控桃芽的休眠与萌发中也发挥重要作用.芽休眠是受多个基因控制的数量性状,涉及多个基因的表达调控.桃休眠相关的MADS-box(DAM)基因簇是桃季节性温度作用和调控休眠开始、结束、冷温感知和花蕾发育速度的关键调控枢纽;短日照和短期低温都会触发DAM基因的表达,同时其表达受一系列调控因子的调节.未来需进一步加强桃需冷量精准预测,完善桃芽休眠的生理调控机制研究,深入研究桃休眠的基因调控网络,以及加快低需冷量桃新品种的选育与推广.
Abstract
Dormancy is an adaptive phenomenon in deciduous fruit trees that stops meristemat-ic activity when encountering adverse environments or seasonal changes,and has important biologi-cal significance and potential economic value.The research on bud dormancy started relatively late,but with the continuous in-depth research on the physiology and molecular biology of fruit trees,studies on the physiological and genetic mechanisms of bud dormancy have received extensive atten-tion.As a model tree species in the Rosaceae family,peach has certain representative significance in the study of bud dormancy.The study of the dormancy mechanism on peach bud is helpful to regu-late dormancy and select new peach varieties with different cold demand to cope with climate change.This article reviews the research progress on peach bud dormancy in recent years,mainly summarizing the factors affecting peach bud dormancy,physiological mechanism and MADS-box(DAM)gene regulating peach bud dormancy,in order to provide a reference for peach bud dorman-cy research.The main environmental factors promoting the dormancy of peach buds are short day and low temperature.The length of dormancy is closely related to the cold amount demand of variet-ies,which is positively correlated with germination and flowering,that is,the lower the cold amount demand,the earlier the germination and flowering,and the higher the cold amount demand,the later the germination and flowering.The 30-bp structural variation in the promoter region of the main con-trolling gene PpDAM6 is highly associated with the cold demand phenotype,and 30-bp deletion ex-ists only in the low cold demand varieties.Long days delays dormancy;high temperature can affect the expression level of genes involved in bud dormancy,thus promoting to remove bud dormancy.The main internal factors are the plant hormones abscisic acid,gibberellin,and metabolites such as carbohydrates,proteins,and volatile substances.The internal factors affecting peach bud dormancy are the plant hormones abscisic acid,gibberellin and metabolites such as carbohydrates,proteins and volatile substances.The key ABA biosynthesis genes,PpNCED1 and PpNCED2,are upregulated during dormancy establishment,downregulated when dormancy is relieved,and decreased with the accumulation of low temperature;in contrast,the expression of ABA degradation genes PpC-YP707A2 and PpCYP707A3 increased with the time of low temperature accumulation,and the ex-pression of these two genes coincides with the trend of ABA content change.GA belongs to the ger-mination-promoting substance and is considered to be the key hormone to regulate the deregulation of bud dormancy.The active gibberellin mainly includes GA1,GA3 and GA4.During dormancy,ABA content decreased,GA content increased,ABA/GA ratio decreased,and minimized when dormancy was relieved,which was mainly caused by the decrease in ABA content.Metabolites such as carbo-hydrates,proteins,and volatile substances play an important role in regulating the dormancy and ger-mination of peach buds.Bud dormancy is a quantitative trait controlled by multiple genes and in-volves regulation of expression of multiple genes.The peach dormancy related MADS-box(DAM)gene cluster is a key regulatory hub for the role of seasonal temperature and regulating the begin-ning,end,cold temperature perception and the rate of flower bud development;both short days and short-term low temperature trigger the expression of DAM gene,while its expression is regulated by a range of regulatory factors.In the future,it is necessary to further strengthen the accurate predic-tion of peach cold amount demand,improve the research on the physiological regulation mechanism of peach bud dormancy,deeply study the gene regulation network of peach dormancy,and accelerate the breeding and promotion of new peach varieties with low cold demand.
维普
万方数据