Shuangshuang Wang1,2, Aiqun Chen3,2, Kun Xie1,2, Xiaofeng Yang1,2, Zhenzhen Luo1, Jiadong Chen1,2, Dechao Zeng1, Yuhan Ren1, Congfan Yang1, Lingxiao Wang1, Huimin Feng1,2, Damar Lizbeth López-Arredondo1,4, Luis Rafael Herrera-Estrella3,4,5, Guohua Xu3,2. 1. State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, 210095 Nanjing, China. 2. Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Ministry of Agriculture, Nanjing Agricultural University, 210095 Nanjing, China. 3. State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, 210095 Nanjing, China; chenaq8@njau.edu.cn ghxu@njau.edu.cn luis.herrera-estrella@ttu.edu. 4. Institute of Genomics for Crop Abiotic Stress Tolerance, Department of Plant and Soil Sciences, Texas Tech University, Lubbock, TX 79409. 5. Laboratorio Nacional de Genómica para la Biodiversidad, Unidad de Genómica Avanzada del Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 36500 Irapuato, Mexico.
Abstract
Low availability of nitrogen (N) is often a major limiting factor to crop yield in most nutrient-poor soils. Arbuscular mycorrhizal (AM) fungi are beneficial symbionts of most land plants that enhance plant nutrient uptake, particularly of phosphate. A growing number of reports point to the substantially increased N accumulation in many mycorrhizal plants; however, the contribution of AM symbiosis to plant N nutrition and the mechanisms underlying the AM-mediated N acquisition are still in the early stages of being understood. Here, we report that inoculation with AM fungus Rhizophagus irregularis remarkably promoted rice (Oryza sativa) growth and N acquisition, and about 42% of the overall N acquired by rice roots could be delivered via the symbiotic route under N-NO3 - supply condition. Mycorrhizal colonization strongly induced expression of the putative nitrate transporter gene OsNPF4.5 in rice roots, and its orthologs ZmNPF4.5 in Zea mays and SbNPF4.5 in Sorghum bicolor OsNPF4.5 is exclusively expressed in the cells containing arbuscules and displayed a low-affinity NO3 - transport activity when expressed in Xenopus laevis oocytes. Moreover, knockout of OsNPF4.5 resulted in a 45% decrease in symbiotic N uptake and a significant reduction in arbuscule incidence when NO3 - was supplied as an N source. Based on our results, we propose that the NPF4.5 plays a key role in mycorrhizal NO3 - acquisition, a symbiotic N uptake route that might be highly conserved in gramineous species.
Low availability of n class="Chemical">nitrogen (N) is oftenpan> a major limiting factor to crop yield in mopan> class="Species">st nutrient-poor soils. Arbuscular mycorrhizal (AM) fungi are beneficial symbionts of mostland plants that enhance plant nutrient uptake, particularly of phosphate. A growing number of reports point to the substantially increased N accumulation in many mycorrhizal plants; however, the contribution of AM symbiosis to plant N nutrition and the mechanisms underlying the AM-mediated N acquisition are still in the early stages of being understood. Here, we report that inoculation with AM fungus Rhizophagus irregularis remarkably promoted rice (Oryza sativa) growth and N acquisition, and about 42% of the overall N acquired by rice roots could be delivered via the symbiotic route under N-NO3 - supply condition. Mycorrhizal colonization strongly induced expression of the putative nitrate transporter gene OsNPF4.5 in rice roots, and its orthologsZmNPF4.5 in Zea mays and SbNPF4.5 in Sorghum bicolorOsNPF4.5 is exclusively expressed in the cells containing arbuscules and displayed a low-affinity NO3 - transport activity when expressed in Xenopus laevis oocytes. Moreover, knockout of OsNPF4.5 resulted in a 45% decrease in symbiotic N uptake and a significant reduction in arbuscule incidence when NO3 - was supplied as an N source. Based on our results, we propose that the NPF4.5 plays a key role in mycorrhizal NO3 - acquisition, a symbiotic N uptake route that might be highly conserved in gramineous species.