苗期水稻和小麦对缺锰胁迫的响应差异及机理

锰是植物生长发育所必需的微量营养元素，缺锰会导致植株矮小，叶片黄化，发育不良等，严重时可致植株死亡。水稻和小麦是我国主要的粮食作物，但种植在有效锰含量不同的土壤中；水稻主要种植在锰有效性高的南方酸性土壤中，小麦主要种植在有效锰含量低的北方石灰性土壤中。为探究水稻和小麦响应缺锰的差异及其机理，本研究采用水培法比较了水稻和小麦苗期在缺锰和加锰处理条件下的生长情况以及植株各部位元素含量和分配情况，并采用绝对定量法比较了小麦和水稻中锰转运基因的表达水平。研究结果表明，与供锰充足的植株相比，缺锰三周严重抑制水稻的生长，而不影响小麦的生长；在缺锰条件下，小麦根到地上部的转运率比供锰充足时提高了16.4%；相反，水稻体内锰从根到地上部的转运率降低了7.5%；苗期小麦根中TaNRAMP2的绝对表达量是水稻OsNRAMP2的3.8-5.1倍。这些结果表明，小麦比水稻更耐缺锰胁迫，这可能与NRAMP2在小麦中的高表达有关。

Differential Tolerance to Manganese-deficiency Stress in Rice and Wheat at Seedling Stage

Manganese (Mn) is an essential microelement for plant growth and development, and its deficiency leads to plant dwarf, chlorosis, dysplasia and so on. Rice (Oryza sativa) and wheat (Triticum aestivum) are two major crops in China, but are grown in soils with different available Mn; rice is mainly cultivated in the southern acidic soil with high Mn availability, while wheat is mainly cultivated in the northern calcareous soil with low available Mn. To explore the difference in response to Mn deficiency between rice and wheat, we compared the growth, element concentration and distribution in different parts of rice and wheat grown in hydroponic culture under Mn-deficiency and -sufficient conditions. Furthermore, we compared the expression level of Mn-related transporter genes in the roots between two species. Compared with plants with sufficient Mn supply at seedling stage, Mn deficiency for 3 weeks resulted in serious growth inhibition in rice, but not in wheat. During Mn-deficient condition, the translocation rate of Mn from root to shoot in wheat increased by 16.4% compared with sufficient Mn supply. In contrast, the translocation rate of Mn from root to shoot in rice decreased by 7.5%. Expression analysis showed that the absolute expression level of TaNRAMP2 in wheat roots was 3.8-5.1 times higher than that of OsNRAMP2 in rice. These results indicate that wheat is more tolerant to Mn deficiency stress than rice through efficient root-to-shoot translocation, which may be associated with higher expression of Nramp2 in wheat.