樱桃根系呼吸代谢响应低氧胁迫的生理与分子机制

Waterlogging damages the crop by causing hypoxia stress. In order to reduce the harm degree, plants with high waterlogging tolerance protected themself from hypoxia stress by changing respiratory pathways, forming aerenchyma and so on. Cherry is the fruit tree with low waterlogging tolerance. Serious physical injuries, even death would caused by even a short time of flooding.Although cherrys are easily to harmed by waterlogging, the damage mechanism is still not clear. Concerning over this problem, four widely used rootstocks which originated different are selected as materials to carry out experiments under hypoxia stress. To ensure the sensitive indicator to hypoxia stress in cherry, the order and degree of root harmed by hypoxia are demonstrate from the changing of subcellular structures such as mitochondria, respiratory metabolism physiological levels and morphology such as root architecture.Finding differentially expressed genes involved in the regulation of cherry root respiration metabolism and closely related to hypoxic damage though non parametric transcriptome sequencing method and digital gene expression profiling (DGE) analysis. Then analysising main biological function of the gene. Combining with the changing of sensitive physiological indexes, screening gene of key enzymes such as PDC. Analysising the relative expression of key genes by using the qPT-PCR technology, then verifying that the function and expression patternof the gene in the network of the gene under hypoxia stress. Finally, revealling the physiological and molecular mechanisms of cherry root respiration metabolism responsing to hypoxia stress, then elucidating the main process and reason that cherry root physiological damage caused by hypoxia.

涝害的实质是由低氧胁迫造成的，耐涝植物可通过改变呼吸代谢途径、形成通气组织等方式应对低氧逆境，降低危害程度。樱桃抗涝性较弱，短时间淹水即会造成严重的生理伤害，甚至死树。针对樱桃易受水涝危害、伤害机理不清的问题，以生产中应用较多、起源不同的4种樱桃为试材，进行低氧胁迫试验。以根系为中心，从线粒体结构、呼吸代谢生理水平、基因表达及根构型等方面，研究低氧造成根系伤害的发生次序及程度，筛选出对低氧敏感的生理指标。通过无参考转录组及数字基因表达谱（DGE）测序分析，查找参与调控樱桃根系呼吸代谢、与低氧胁迫密切相关的差异表达基因，分析其执行的主要生物学功能。结合低氧敏感生理指标的变化，筛选PDC等关键酶基因，利用qRT-PCR技术进行关键基因的相对表达量分析，验证其在低氧胁迫下基因网络中的功能及表达模式。最终，揭示樱桃根系呼吸代谢响应低氧胁迫的生理与分子机制，阐明低氧造成根系生理伤害的主要环节及原因。

我国甜樱桃发展迅速,期间由于对园址选择重视不足,生产中经常因集中降雨，果园排水不良，引发根系呼吸障碍，最终导致植株死亡甚至毁园。为了评价水涝对樱桃根系的伤害程度，揭示其不耐涝的生理与分子机制，探讨相应的调控措施。以东北山樱等为试材，通过淹水模拟夏季降雨、果园积水，研究了根系呼吸代谢系统在短期水涝、涝后恢复阶段的变化特征，探讨了水涝伤害的分子作用机制。结果表明：.水涝引起的低氧胁迫造成樱桃根系生理伤害具有明显的时间效应。淹水初期的3 h内樱桃根系活力无明显变化，6h时活力下降。其中东北山樱对淹水反应最为敏感，24 h时根系呼吸速率和根活力显著下降。通过转录组数据分析发现，淹水后根系中大量的差异基因富集到糖酵解/糖异生通路， 3 h时参与水涝信号传导的RAP2.2和Ps-CIPK关键基因显著上调，6h内己糖激酶、丙酮酸脱羧酶、乙醇脱氢酶等参与呼吸代谢关键酶活性和相关基因表达量增加，说明糖酵解/糖异生过程在樱桃应对短期水涝胁迫过程发挥重要调控作用，即6h内仍可维持较高水平的非结构性碳水化合物、能荷与ATP供给。淹水24 h由于根系中发酵途径效率较低，消耗了大量的可溶性碳水化合物，而陷入严重的能量危机。淹水1d后解除水涝条件，东北山樱根系功能恢复过程中会出现ROS迸发现象，虽然其能量水平在解除水涝后1d左间时间可基本恢复到正常状态，但因ROS大量积累仍会对植株造成明显伤害，RBOH家族参与了涝后恢复过程中活性氧代谢。通过添加GABA及亚精胺可调控东北山樱根系内氮代谢水平，一定程度上能够提高根系应对水涝胁迫的能力，但不足以解除因ROS积累对植株造成的伤害。.综上，要充分重视樱桃园址选择问题，避开雨季易积水地块，水涝发生后6小时内要启动排水措施、通气，以维持根系大部分生理功能，淹水超过1d难以恢复根系功能。