【作者】 陈凯；

【导师】 练兴明；

【作者基本信息】 华中农业大学 ， 生物化学与分子生物学， 2019， 硕士

【摘要】 水稻是最重要的粮食作物之一,全球约有一半以上人口将稻米作为主食。然而,随着土壤重金属镉污染加剧,使得稻米镉含量超标的问题日益严重。镉元素在人体内的代谢半衰期较长且具有很强的生物毒性,它通过食物链进入人体后会直接威胁人们的健康。因此,研究镉元素在水稻体内吸收和转运的机制,对培育低镉积累的优质水稻品种来说具有重要意义。在本研究中,我们对水稻镉积累相关基因OsHMD1进行功能研究,主要结果如下:1.RT-qPCR结果显示,OsHMD1在水稻不同生育时期的各个组织中均有表达。GUS染色结果表明,OsHMD1_Pro:GUS在水稻根部的中柱、内皮层和厚壁组织以及叶片的木质部附近薄壁细胞中表达。OsHMD1在镉胁迫处理下受到诱导表达,而在高浓度铁、锰和锌的胁迫处理下表达量不受影响。2.在镉胁迫处理下,突变体和超量表达植株与野生型相比均没有显著的表型差异（包括株高、根长、不定根数和生物重）。在镉浓度梯度处理下,oshmd1突变体植株与野生型相比根部和地上部的镉浓度均显著增加。进一步研究发现,oshmd1突变体植株木质部伤流液的镉浓度也显著增加。这些结果表明,OsHMD1影响了水稻根部和地上部镉的积累。3.与野生型相比,oshmd1突变体植株成熟期叶片与叶鞘中的镉浓度显著降低,而节点与节间中的镉浓度显著增加。这些结果表明,OsHMD1影响镉在地上部组织的分配。4.在酵母镉敏感突变体Δycf1中,异源表达OsHMD1提高了酵母对镉的耐受性。元素含量测定分析显示,异源表达OsHMD1降低了酵母细胞的镉浓度。综上所述,我们的研究结果表明,OsHMD1可以促进镉元素在水稻根部和地上部的积累以及影响镉在地上部组织中的分配。更多还原

【Abstract】 Rice(Oryza sativa L.)is one of the most important crops and it is a staple food for half of the world’s population.With increasing contamination of cadmium in paddy field,the phenomenon of excessive cadmium content in rice is widespread.The biological half-life of cadmium(Cd)in the human is estimated to be nearly 30 years,which leads to chronic toxicity.Cadmium accumulates in the human through the food chain and causes serious health problems.Thus,molecular understanding of cadmium transport in plants will enable the developing of low-Cd-crops.In this study,we investigated the function of the OsHMD1 in rice.The main results are summarized as follows:1.Reverse transcription quantitative PCR(RT-q PCR)analysis showed that OsHMD1 was expressed in most rice organs throughout the growth period of rice grown.Transverse sections of roots showed that the pericycle,endodermis and sclerenchymatous layer had the highest GUS activity,whereas the GUS activity also was found in leaf parenchyma cells surrounding the xylem.The expression of OsHMD1 was induced by excess cadmium but was not signifcantly affected by high concentrations of iron,manganese or zinc.2.We compared the cadmium tolerance of OsHMD1 transgenic lines with that of the wild type under different cadmium concentrations.The OsHMD1 transgenic lines showed no apparent phenotypes compared with the wild type.To evaluate cadmium accumulation,the transgenic lines were grown in a nutrient solution containing different cadmium concentrations treatment.Element concentration analysis using inductively coupled plasma mass spectrometry(ICP-MS)showed that the cadmium concentrations were signifcantly higher in the shoots or roots of three independent oshmd1 mutant lines compared with wild-type plants.In the oshmd1 mutants,the cadmium concentrations in xylem sap were signifcantly higher than those in the wild type at each treatment.These results showed that OsHMD1 affected the accumulation of Cd in roots and shoots.3.At the harvest,the concentration of cadmium in the leaf blade and leaf sheath was significantly decreased in the mutant lines.The concentration of cadmium in the node and internode was slightly higher in the mutant lines.These results demonstrated that OsHMD1 affects the distribution of cadmium in shoots.4.Heterologous expression OsHMD1 in the Cd-sensitive yeast mutant strain Δycf1increased its cadmium tolerance at different cadmium concentrations treatment.When treated with cadmium,the Cd concentration in cells expressing OsHMD1 were signifcantly lower than those in cells expressing the empty vector control.These results suggest that OsHMD1 increases the tolerance to cadmium by decreasing their concentrations in the yeast cells.In conclusion,our results suggested that OsHMD1 is involved in the accumulation and distribution of Cd in rice.更多还原