Integrated omics analysis of rice gene expression profiles and microRNAs identifies crucial target genes for nitrogen use efficiency [Next Gen Genomics Facility]

Nitrogen use efficiency is a complex trait in rice involving nitrogen uptake, utilization, and assimilation. The coding mRNAs and non-coding regulatory RNAs have combinatorial involvement in molecular mechanisms underlying nutrient use efficiency. In this study, we generated the microRNA expression profiles of panicle tissues in N-efficient (Basmati370, Thurur bhog) and non-efficient genotypes (Kola Joha3, IC463254) at the booting stage using microRNA sequencing and microarray expression profiles of root and shoot tissues at the seedling stage in N-efficient (Varadhan) and non-efficient (Prasanna) genotypes under hydroponic condition with N (+) and without N supplementation N (-) using Affymetrix rice microarray chip. To understand holistically the differential expression of mRNAs and microRNAs regulating NUE, we integrated the newly generated microRNA sequencing and microarray datasets with earlier generated mRNA gene expression profile data using bioinformatics tools. We present a consolidated set of genes operating tissue and stage-wise in rice for NUE. The microRNAs viz. miR2118o, miR1442, miR5149 were up-regulated and miR164, miR2867, miR171i were down-regulated in N efficient genotypes under low N conditions. Interestingly, we have identified the consistent differential expression of known and novel microRNAs in N efficient genotypes viz. miR1859 (down-regulated), miR1441, miR3979-5p, miR5149 (up-regulated) under low nitrogen conditions. The GARP-MYB/SANT domain, early nodulin genes were exclusively present in the shoot of Varadhan; genes related to polycomb complex, enhancer of zeste, were downregulated under N0 condition. Under low N conditions, brassinosteroid insensitive receptor kinase-1, IAA31, DUF581, DUF617, DUF803, NIN, nodulin, oligopeptide transporter, OsPOP1, calmodulin kinases were upregulated across roots and shoots. The genes upregulated in efficient genotypes expressed in shoots as well as in panicle tissues and regulated by downregulation of their miRNAs are targets for further studies. Remarkably, the downregulation of specific metabolic pathways was observed as an adaptive strategy to cope with nitrogen limitation, highlighting the complexity of NUE regulation in rice. These findings elucidate the intricate molecular networks governing NUE in rice and underscore the potential of specific microRNAs and genes as targets for precision breeding strategies aimed at enhancing nitrogen utilization efficiency in rice cultivation. The integrative transcriptomic approach presented here provides a foundation for further functional genomic studies, facilitating the development of novel breeding strategies to optimize NUE in rice.