Identification of a novel D3 allele playing a role in nitrogen utilization

Tillering is an important agricultural trait in rice and can affect grain yield. Therefore, screening and identification of mutants in tiller-associated traits are crucial for understanding the development of rice tillers. In this study, we identified a new allelic mutant of d3 with phenotypic characteristics influenced by exogenous nitrogen. The j30 mutant harbors a G-to-A base substitution at position 1900 of the coding sequence for LOC_Os06g06050, resulting in an amino acid conversion from Asp to Asn, being a new allelic mutant of d3 . During the whole growth period, j30 displayed multiple characteristic variations, including dwarfism, thinner stems, narrower leaves, more tillers, etc. Compared with wild-type (WT) counterparts, the leaf blades and culms of j30 consisted of fewer vascular bundles with shorter distances between them. Quantitative polymerase chain reaction (qPCR) analysis revealed that, in the mutant, N-fertilizer could extremely upregulate expression of the N-pathway-related glutamine synthetase gene GS1;3 and reduce the transcription of high-affinity nitrate transporter genes ( OsNRT2.2 and OsNRT2.3a were downregulated before N treatment) to sparse expression. The catalase-encoding gene CATA alone displayed a lower transcriptional level in j30 when treated with N-fertilizer, while CATB and CATC showed higher expression and CATA no difference compared with before N-fertilizer treatment.