In silico Analysis of OsNRT2.3 Reveals OsAMT1.3, OsZIFL9, OsbZIP27, and OsIRT1 as Potential Drought-related Genes During Nitrogen Use Efficiency in Oryza sativa L.

Nitrate transporter (NRT) is responsible for the molecular mechanism of the root nitrate (NO3-) uptake system for plant development. Although several NRT genes are identified and characterised in plants, knowledge of the NRT2 gene family and its nitrogen use efficiency (NUE) function in drought stress has remained elusive in rice. This study conducted an in silico analysis on 20 NRT2 family genes of rice, wheat, soybean, barley, maize, and papaya. Phylogenetic and motifs analysis clustered genes encoding NRT2 proteins into four monophyletic groups, and the motifs of NRT2 genes were significantly conserved for the specific domain of NO3- transmembrane transporter. Interestingly, co-expression analysis revealed that potential drought-related genes were expressed similarly to the functional NUE gene, OsNRT2.3. Furthermore, half of the co-expressed genes were enriched in nitrogen use efficiency (NUE)-related processes, such as transport, stress, macromolecule metabolic pathways, and transcription regulation. Expression pattern analysis of OsNRT2.3 and its co-expressed genes in tissue-specific and nitrogen (N) response led to the discovery of OsAMT1.3, OsZIFL9, OsbZIP27, and OsIRT1 as four strong candidates to participate in drought stress during NO3- uptake system. The co-expression of iron (Fe) uptake genes, OsZIFL9 and OsIRT1, with OsNRT2.3 also suggested a possible interaction of Fe and nitrogen (N) during an increasing amount of Fe, which led to the acidification of rice apoplasts during water deficiency. Together, this study will provide a valuable resource for potential candidate genes that can further investigate their molecular response to drought during NUE.