【作者】 王振宇；

【导师】 李凤民；

【作者基本信息】 兰州大学 ， 生态学， 2009， 博士

【摘要】 全球范围内，干旱是限制作物生长和产量的主要因子。植物对水分亏缺的响应是复杂的，其包括许多方面，如胁迫感知、信号传递、生长和生物量分配方式的改变、植株水分状态的动态平衡、气孔导度和二氧化碳同化作用的降低、渗透调节以及解毒过程。本文应用生理生态及分子生物学方法研究了植物根源信号及叶片表皮层与植物耐旱性的关系。在生理生态水平上，主要研究了非水力根源化学信号土壤水分阈值与作物耐旱性的关系由植物氧化胁迫信号调节。在分子水平上，通过筛选逆境胁迫相关的拟南芥突变株，克隆并研究了基因BDG1及表皮层合成途径在植物逆境胁迫中的功能。利用人工生长箱对盆栽冬小麦(碧玛1号，小偃6号和陕229)在拔节期进行逐渐水分干旱处理，通过对不同年代冬小麦品种的根源信号特征进行比较，发现土壤水分亏缺引起明显的非水力根源化学信号和水力信号现象。根源化学信号和水力信号相继出现时的土壤相对含水量临界值随不同年代冬小麦品种出现有规律的变化趋势，其变化区间为70％—45％FWC(Field water capacity)之间。现代小麦品种陕229具有较宽的水分阈值，为46.2-70.8％FWC(差值为24.6％)，而古老小麦品种碧玛1号具有较窄的水分阈值，为50.6-64％FWC (差值为13.4％)，近代小麦品种小偃6号居于中间，阈值为50.4-69.9％FWC(差值为19.5％)。盆栽干死试验表明在充分供水条件下同时停止供水，土壤水分逐渐下降，盆内植物自然干死。现代小麦品种陕229存活时间较长，为22.7天，而古老小麦碧玛1号品种存活天数最短，为15.3天。通过对地上部生物量比较发现现代品种陕229地上部生物量由干旱引起的降低程度(20.9％)较古老小麦品种碧玛1号(37.3％)轻，说明现代小麦品种陕229具有较高的耐早性。通过活性氧及氧化清除酶的分析表明现代小麦品种陕229在逐渐干旱处理期间具有较少的活性氧增加以及更多的氧化清除酶产生，而古老品种小麦碧玛1号则具有较高的活性氧水平和较低的氧化清除酶含量。结果说明现代小麦品种陕229具有较早的感应干旱信号并及时调节活性氧动态平衡以提高作物的耐旱性。通过筛选拟南芥突变株，基因定位结果显示red1突变基因是BDG1基因的一个新的等位基因，该基因编码alpha-beta水解酶，调控植物表皮层合成。red1突变体在渗透胁迫条件下具有较低的ABA含量，基因表达分析结果表明ABA合成基因NCED3在该突变体中表达水平降低，同时在不同胁迫，如冷害胁迫、ABA、PEG和盐处理条件下胁迫响应基因RD29A，RD22，COR15a，COR47，KIN1，P5CS1和RAB18表达水平降低。表型分析表明该突变体萌发及萌发后生长对A B A，盐及渗透胁迫较野生型敏感，同时离体失水及耐早性实验表明该突变体具有较快的蒸腾失水和较低的耐旱性。通过分析A B A合成信号转导基因表达水平，表明在不同浓度PEG处理下B D G 1基因调节A B A合成和信号转导途径基因水平表达。基因芯片分析表明在该突变体中一部分关于A B A信号转导的有显著的提高或降低，说明该基因在植物A B A信号转导途径中具有重要的作用。因为该基因功能为形成植物表皮层，我们通过遗传手段分析表明其他编码合成表皮层基因的突变体同样对渗透胁迫较敏感，基因表达分析ABA合成和信号转导基因水平在突变体中均较相对应的野生型低，说明编码合成表皮层的基因在渗透条件下影响A B A合成和信号转导。综上所述表明在渗透条件下，表皮层合成受阻将激发一种信号，从而调节A BA合成和信号转导途径，说明表皮层对于植物响应干旱、渗透胁迫是一个重要的因子。更多还原

【Abstract】 Drought is one of the most important constraints limiting the growth of plants andecosystem productivity around the world. Plant responses to water deficit are complex andencompass many aspects, including stress sensing and signaling, changes in growth andbiomass allocation patterns, water status homeostasis, decreased stomatal conductance andCO2 assimilation, osmoregulation, and detoxification processes. In this study, relationshipbetween root chemical signal or leaf epicuticular and drought tolerance was investigated byusing eco-physiology and molecular biology method. In eco-physiology level, we are mainlyfocused on the soil water threshold range of chemical signals and drought tolerance wasmediated by reactive oxygen species (ROS) homeostasis. In molecular level, we screenedsome mutants in response to abiotic stress in Arabidopsis. Also, we used map-based cloningto map the gene BDG1 and functional analysis of cuticle pathway which has important role inabiotic stress.A pot experiment was used to investigate the homeostasis between ROS and antioxidantdefense at five harvest dates, and its role in the correlation between soil-water threshold rangeof chemical signals and drought tolerance in three wheat (Triticum aestivum) cultivars duringprogressive soil drying. The cultivars were bred at different periods, cv. BM1 (old), cv.Xiaoyan6 (recent) and cv. Shah229 (modem). They were treated with progressive soil drying.Shoot biomass was affected by drought imposed by two water treatments (90 and 55% fieldwater capacity). The modern wheat cultivar had a lower ROS content and higherROS-scavenging antioxidant capacity with greater soil drying (68-25% soil water content)compared with the older cultivar. The modern cultivar also had excellent adaptation todrought, with a longer survival of 22.7 d and less reduction in shoot biomass of 20.9%, due toearly chemical signals and better balance between ROS production and antioxidants. Theolder cultivar had survival of 15.3 d and 37.3% reduction of shoot biomass. Wider soil-waterthreshold range of chemical signals was positively correlated with improved droughttolerance and better ROS homeostasis. These results suggest that ROS homeostasis acts as a regulator in relationships between soil-water threshold range of chemical signals and droughttolerance.The endogenous ABA level plays a key role in various stress responses including theregulation of these processes is partially mediated by change of de novo ABA biosynthesis.However, regulation of NCED3 gene was not fully elucidated until now. We used a luciferasereporter system to screen a lot of mutants in response to various abiotic stresses. One ofmutant, name red1, was reduced ABA content and decreased NCED3 expression level. Stressphenotype analysis showed that redl was sensitive to osmotic stress, ABA, salt treatment ingermination and post germination growth. Northern blot analysis of stress-responsive genesshowed thatRD29A, RD22, COR15a, COR47, KIN1, P5CS1和RAB18 was reduced inred1 mutant plants under osmotic stress treatment. Furthermore, red1 mutant plants have fasttranspiration water loss and reduced drought resistance to drought. Map-based cloning of red1shows that it is a new allele of BDG1, which has a role in the formation of cuticle. Furtherstudies on the redl mutant plants showed that it impairs the osmotic stress regulation of ABAbiosynthesis and ABA signaling genes by RNA gel blot and microarry analysis. In addition,genetic analysis of other cuticle mutants showed that all of these mutants were sensitivity toosmotic stress, and RNA gel blot analysis indicated that these mutants also impair the osmoticstress regulation of ABA biosynthesis and ABA signaling genes. In conclusion, we identifieda novel pathway that it could regulate the ABA biosynthesis and ABA signaling pathwayunder osmotic stress treatment.更多还原