The Molecular Mechanism Research On The Synergistic Improvement Of Rice Water Utilization By Nitrogen Treatment And PRD Technology

Rice,a major food crop,has high water consumption but only 30%-40% water utilization.It was found that the adverse effects of water stress could be mitigated by partial root-zone drying(PRD)and additional nitrogen fertilization.To investigate the molecular mechanism of nitrogen treatment and PRD to regulate water use in rice,this paper used rice variety Meixiangzhan 2 as experimental material to determine the physiological and biochemical changes of the plant under different water conditions and nitrogen form co-treatment,and to determine the appropriate nitrogen ratio.Under these ratios,a multi-omics analysis combining transcriptome and metabolome was used for the first time to initially reveal the nitrogen morphology and PRD-mediated transcriptional and metabolic regulatory networks,providing a theoretical basis for the development of new water-saving technologies.The main results are as follows:(1)The results showed that water stress treatment resulted in significantly lower water content in roots than normal moisture and PRD treatments under different nitrogen treatments,while in PRD treatment,the water content of roots was almost not significantly different from normal moisture treatment;in leaves,PRD treatment also resulted in significantly lower water content than normal moisture treatment,however,the water content in leaves was still significantly increased compared to water stress treatment.Changes in chlorophyll content also followed a similar trend to that of water content.Water stress treatment resulted in significantly lower chlorophyll content in leaves than normal water and PRD treatments,but in PRD treatment,chlorophyll content was almost not significantly different from that of normal water treatment.The changes in superoxide dismutase activity in the leaves also showed similar trends with chlorophyll content and water content.However,the content of malondialdehyde(MDA)was the opposite,and the water stress treatment resulted in significantly higher MDA content in the leaves of almost all treatments than in the normal water and PRD treatments,while in the PRD treatment,the content of MDA was not significantly different from the normal water treatment.(2)Clustering and enrichment analysis of transcriptome and metabolome showed that the transcriptional and metabolic differences caused by PRD or water stress treatments were mainly in the roots,with normal water roots and PRD-treated water half roots showing similar transcriptional and metabolic patterns,while PRD-treated drought half roots and water-stressed roots also showed similar transcriptional and metabolic patterns.metabolic differences induced by PRD or water stress treatments in the roots were mainly concentrated in glycolysis,mannitol and fructose,chlorophyll,and nitrogen and amino acid metabolism pathways.(3)To further elucidate the mechanisms by which PRD and nitrogen morphology synergistically regulate water use in rice,gene co-expression modules were jointly analyzed with metabolic clustering.For example,Oryza sativa NIN-LIKE PROTEIN1(OsNLP1)and its target genes were both highly expressed in water-stressed roots.Oryza sativa NIN-LIKE PROTEIN 3(OsNLP3)and its target genes were both highly expressed in normal water-stressed roots and leaves;ion-related transcription factors 2and 3(IRO2/3)and their target genes were highly expressed in water-stressed roots;Oryza Sativa Homeobox 15 gene(OsH15)and its target genes were highly expressed in both water-stressed and normal water roots,but brassica and lignin-like metabolites were less expressed;Wrin-Kled 1(WRI1a)and its target genes were higher in PRDtreated roots,and the same trend was observed for glycans;Diterpenoid Phytoalexin factor(DPF)and its target genes and terpenoids were higher in water-stressed roots.(4)The target gene sets of the 12 identified transcription factors were further analyzed in comparison with the identified co-expression modules.The results showed that there was a significant enrichment of target genes for several transcription factors,and these functional genes were closely associated with processes such as water use or drought response through regulation of ABA signaling,ethylene signaling,and nitrogen partitioning,for example,Teosinte branched1/Cincinnata/proliferating cell factor19(TCP19)was highly expressed in PRD-treated plants,biological clock binding factor Oryza Sativa Circadian Clock Associated 1(OsCCA1)was highly expressed in normal water plants,and ABRE binding factor 1/2(ABF1/ABF2)were induced to be highly expressed in water stress and PRD treatments,the stress-induced RNA-binding protein Tandem CCCH zinc finger(OsTZF7)was highly expressed in water-stressed roots,and Oryza Sativa Drought-responsive Ethylene response factor 1(OsDERF1)response was strongly induced in water-stressed roots,and these transcription factors regulated target genes up-or down-regulated multiple genes;high expression of LUGULELESS 2(LG2)in normal water and PRD-treated roots induced only up-regulated expression of genes.In summary,by analyzing the physiological,transcriptional and metabolic results,we found that the regulatory mechanism mediated by PRD occurs in the root,indicating that other molecular mechanisms besides ABA-mediated drought tolerance are involved in the PRD-mediated regulatory mechanism.We provide new insights into PRD-mediated osmotic stress tolerance and identify genes that contribute to further improvement of water use or drought tolerance in rice: OsNLP1,ABF1,TCP19,OsDERF1,LG2,etc.