水稻氮素吸收低效型突变体osnad1的生理和遗传分析

水稻突变体osnad1（Oryza sativa nitrogen absorption deficit 1）是从经EMS诱变的水稻突变体库中筛出的一株性状稳定遗传的氮素吸收低效型突变体,为了进一步明确其生理和遗传特性,本研究从表型分析、氮代谢生理、光合特征和遗传分析等4个方面对突变体osnad1及其野生型日本晴（Nippenbare）进行了比较。研究结果表明：（1）与野生型相比,突变体osnad1株高降低,根系长度缩短,叶色发黄,植株生长受阻;（2）与野生型相比,突变体osnad1植株体内总氮积累量大大降低,通过扫描离子选择性电极技术（scanning ion-selective electrode technique,SIET）对其根系表面氮源离子净流动速率的测定发现,osnad1根系对NH₄ ⁺的吸收速率较野生型大幅降低。突变体osnad1根系中谷氨酰胺合成酶（GS）活性随之降低。（3）与野生型相比,突变体osnad1叶片中叶绿素a、叶绿素b、类胡萝卜素含量降低,一系列光合相关参数,如净光合速率、气孔导度、胞间二氧化碳浓度和蒸腾速率降低,干物质积累受阻。（4）遗传分析结果表明：F₂群体中正常表型与突变表型植株数量之比符合单基因突变的3∶1。综合上述,突变体osnad1是一个氮吸收低效型的单基因隐性水稻突变体,该研究为后续的基因克隆及其功能分析提供参考。

Physiological and Genetic Analysis of Rice Mutant osnad1 Defective in Nitrogen Absorption

To reveal the mutation type and genetic characteristics of rice mutant osnad1 (Oryza sativa nitrogen absorption deficit 1) generated by ethylmethane sulfonate (EMS) mutagenesis, we compared the phenotypes, nitrogen metabolism and photosynthesis between the mutant osnad1 and wild type (WT, Nipponbare), and conducted the genetic analysis of osnad1 in this study. The results showed that: (1) Compared with WT, the phenotype of osnad1 plant showed a decrease of plant height and root length, leaves chlorosis, and restrained growth. (2) The accumulation of total nitrogen in roots and shoots of osnad1 was significantly less than that in WT. Through determining the flow rate of nitrogen source ions (NH₄ ⁺ and NO₃ˉ) on root surface of osnad1 and WT by SIET technique, we found that the capacity of nitrogen absorption and the glutamine synthetase (GS) activity in osnad1 root were lower than that in WT. (3) Compared with WT, both the contents of chlorophyll and photosynthetic parameters were decreased in leaves of osnad1, causing accumulation of dry matter blocked. (4) The result of genetic analysis showed that the ratio of normal plant number to mutant plant number was 3:1. In conclusion, osnad1 was a rice mutant defective in nitrogen absorption, which was controlled by a single recessive gene. This study would provide a base for further cloning and function analysis of the osnad1 gene.