[Functional analysis of a nitrate-induced GARP transcription factor AhNIGT1.2 in peanut nodulation].

Peanut, a major economic and oil crop known for the high protein and oil content, is extensively cultivated in China. Peanut plants have the ability to form nodules with rhizobia, where the nitrogenase converts atmospheric nitrogen into ammonia nitrogen that can be utilized by the plants. Analysis of nodule fixation is of positive significance for avoiding overapplication of chemical fertilizer and developing sustainable agriculture. In this study, ., a member of the family predominantly expressed in peanut nodules, was identified by bioinformatics analysis. Subsequent spatiotemporal expression analysis revealed that . was highly expressed in nodules and showed significant responses to high nitrogen, low nitrogen, high phosphorus, low phosphorus, and rhizobia treatments. Histochemical staining indicated that the gene was primarily expressed in developing nodules and at the connection region between mature nodules and peanut roots. The fusion protein AhNIGT1.2-GFP was located in the nucleus of tobacco epidermal cells. The .-OE significantly increased the number of peanut nodules, while .-RNAi reduced the number of nodules, which suggested a positive regulatory role of AhNIGT1.2 in peanut nodulation. The .-OE in roots down-regulated the expression levels of ., ., , and , which indicated that . influenced peanut nodulation by modulating nitrate transport and the expression of genes. The transcriptome analysis of .-OE and control roots revealed that overexpressing . significantly enriched the differentially expressed genes associated with nitrate response, nodulation factor pathway, enzymes for triterpene biosynthesis, and carotenoid biosynthesis. These findings suggest that . play a key role in peanut nodulation by regulating nitrate transport and response and other related pathways. This study gives insights into the molecular mechanisms of nitrogen and phosphorus in regulating legume nodulation and nitrogen fixation, and sheds light on the development of legume crops that can efficiently fix nitrogen in high nitrogen environments.