Abstract
Over-application of nitrogen (N) fertilizer in fields has had a negative impact on both environment and human health. Domesticated rice varieties with high N use efficiency (NUE) reduce fertilizer requirements, enabling sustainable agriculture. Genome-wide association study (GWAS) analysis of N absorption and utilization traits under low and high N conditions was performed to obtain 12 quantitative trait loci (QTLs) based on genotypic data including 151,202 single-nucleotide polymorphisms (SNPs) developed by re-sequencing 267 japonica rice varieties. Eighteen candidate genes were obtained by integrating GWAS and transcriptome analyses; among them, the functions of OsNRT2.4, OsAMT1.2, and OsAlaAT genes in N transport and assimilation have been identified, and OsJAZ12 and OsJAZ13 also play important roles in rice adaptation to abiotic stresses. A NUE-related candidate gene, OsNAC68, was identified by quantitative real-time PCR (qRT-PCR) analyses. OsNAC68 encodes a NAC transcription factor and has been shown to be a positive regulator of the drought stress response in rice. Overexpression of OsNAC68 significantly increased rice NUE and grain yield under deficient N conditions, but the difference was not significant under sufficient N conditions. NUE and grain yield significantly decreased under both N supply conditions in the osbnac68 mutant. This study provides crucial insights into the genetic basis of N absorption and utilization in rice, and a NUE-related gene, OsNAC68, was cloned to provide important resources for rice breeding with high NUE and grain yield.
Highlights
Rice is the most important food crop in the world, and sustainable and healthy crop development is important for global food security
Behind the substantial increase in rice yield, excessive and unreasonable N fertilizer input has incurred a series of problems, such as the decline in nitrogen use efficiency (NUE), the increase in production costs, and air and water pollution, which seriously affect sustainable rice production
Many NUE-related genes in rice have been discovered by quantitative trait locus (QTL) mapping and genome-wide association studies (GWASs) (Xu et al, 2012; Li et al, 2017)
Summary
Rice is the most important food crop in the world, and sustainable and healthy crop development is important for global food security. Nitrogen (N) is an important limiting element in rice production and plays an important role in Nitrogen Use Efficiency the growth and yield of rice. Behind the substantial increase in rice yield, excessive and unreasonable N fertilizer input has incurred a series of problems, such as the decline in nitrogen use efficiency (NUE), the increase in production costs, and air and water pollution, which seriously affect sustainable rice production. Through cloning and functional identification of these genes, the in-depth study of their mode of action and regulatory mechanisms has laid a good foundation for improving rice NUE-related research and has important theoretical significance and practical application value (Gao et al, 2019, 2020; Tang et al, 2019; Guo et al, 2020; Yu et al, 2020)
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