小麦苗期氮素响应的生理及分子差异研究

Physiological and molecular differences of nitrogen response in wheat seedlings

为探明小麦幼苗对不同氮素浓度的响应差异,设置高、低2种氮素浓度对12个不同基因型小麦进行营养液沙培,研究不同处理间小麦幼苗植株鲜重、叶片叶绿素含量、根系形态等的差异,并对植株谷氨酰胺合成酶(GS)活性以及氮素吸收利用相关基因表达差异进行分析;同时,根据不同基因型小麦材料的植株鲜重对其氮素利用效率进行评价。结果表明,氮素充分供应可显著提高植株鲜重;低氮条件下植株根冠比显著大于高氮水平下数值;氮素缺乏可以促进主根伸长、总根长和总根表面积的扩大,且不同基因型间主根长度差异显著。幼苗的叶绿素含量随着氮素浓度升高而增加。不同氮素浓度处理下小麦幼苗叶片的谷氨酰胺合成酶活性在小麦各基因型间表现不同。小麦TaNRT1.1和TaNRT2.1基因在低氮处理下表达量较高,且高氮效材料郑麦9023和“410187”中2个基因的转录量高于低氮效材料南农08Y611中的转录量。氮素浓度正向调控氮素同化基因TaGS2的表达,而TaGS1表达量则在基因型间和氮素处理间差异不大。

To better understand the response mechanism of wheat seedlings under different nitrogen levels,a panel of 12 different wheat genotypes was set to grow under contrast nitrogen input levels by using the Hoagland nutrition solutions with sand.The seedling biomass,root morphology,chlorophyll content of the leaves,the leaves GS enzyme activity as well as the transcripts of the central genes involved in nitrogen uptake and assimilation process were investigated.The results indicated that the seedlings biomass of all the wheat genotypes was significantly increased upon the increase of the nitrogen input.The seedling root/shoot ratio under the low nitrogen level was higher than that under the high nitrogen levels.Although significant difference was observed for the main root growth between the different genotypes under the nitrogen-deficiency conditions,it was found that the nitrogen deficiency stimulated the main root growth and expanded the total root length and total root surface of the wheat seedlings on the whole.Meanwhile,the chlorophyll con⁃tent of the individual wheat lines were elevated upon the increase of the nitrogen input.However,the GS enzyme activity demonstrated genotypic variations under contrasting nitrogen levels.The gene expression of TaNRT2.1 and TaNRT1.1 exhibited higher transcript un⁃der low nitrogen conditions.Furthermore,the transcripts of TaNRT2.1 and TaNRT1.1 were higher in the high nitrogen use efficiency wheat lines of Zhengmai 9023 and“410187”than the low nitrogen use efficiency wheat line of Nanong 08Y611.In spite of up-regula⁃tion of TaGS2 was observed under high nitrogen levels,no significant differences were detected for the expression of TaGS1 with re⁃spect to the genotype or the nitrogen levels.