Transcriptome Sequencing Of Seeding Foxtail Millet Response To Low Nitrogen Stress And Characteristics Analysis Of Protein Phosphatease2C (PP2C) Gene Family In Foxtail Millet

Nitrogen is one of the most essential nutrients involved in plant growth and development.The low nitrogen uptake and use efficiency is an important factor limiting crop yieldincrease.Therefore, uncovering the regulatory mechanisms of plant response to low nitrogenhas important theoretical significance for cultivating crops of nitrogen efficient varieties.Foxtail millet (Setaria italica) exhibits special characteristics of being stress tolerant,eurytopic and with small genome, which makes it an appropriate species for studying theunderlining mechanism of stress responses in plants. Phenotypes of23foxtail millet materialsunder low nitrogen treatment were analyzed, and the transcriptome of variety resistance tolow nitrogen was sequenced for further screening of genes involved in low nitrogen stressresponse.The main results are as follows:1. In this study, H214was screened as the most nitrogen deficiency tolerant material viaanalysis of plant height, biomass, total root length and root surface area btween23foxtailmillets.2.28983genes were identified within nitrogen deficiency transcriptome sequencing inseeding H214, which covered71.39%of the reference genome. Most of the1889genes withdifferent expression levels were cytochrome P450, protein kinases and transcription factors,and among them,1097genes were annotated to112pathways, mainly including biosynthesisof secondary metabolites, plant-pathogen interaction, plant hormone signal transduction.Thisresult indicated the interactions between signaling and metabolic pathways in response tostresses, and these different expression genes can be used for screening candidate genesinvolved in nitrogen stress response.3. Transcriptome sequencing demonstrated that PP2C genes wered involved in nitrogenresponse. In this study,80candidate PP2C genes were identified from foxtail millet genomevia sequence alignment, and phylogenic tree analysis showed that PP2Cs in foxtail milletwere divided into12subfamilies.Gene expression profiling showed that the10members of subfamily A were induced byABA, drought, high salt, cold and nitrogen deficiency. Promoter analysis identified a variety of cis-acting elements involved in stress responses in promoter region of members insubfamily A, and a specific element responding to low nitrogen stress was identified in thepromoter region of SiPP2CA5, SiPP2CA6, SiPP2CA7, and SiPP2CA8.In this study, SiPP2CA8showed strong response to all of stresses treatment, and itsexpression stayed at high level under low nitrogen stress. Further study demonstrated thatSiPP2CA8was mainly expressed in root. Subcellular localization showed that SiPP2CA8waslocalized in cytomembrane, cytoplasm and nucleus. Bimolecular fluorescencecomplementation (BiFC) assay demonstrated that SiPP2CA8interacted with an ABA receptorlike protein, SiRCAR3(gene locus Si018317m.g) in cytomembrane, cytoplasm and nucleus.These results suggested that SiPP2CA8may participate in ABA signaling in foxtail millet.This study provided an important basis for further screening for novel stress-resistantgenes and studying on the regulation mechanism of stress-resistance.