Cell-specific pathways recruited for symbiotic nodulation in the Medicago truncatula legume

In the originally published version of this work,a mistake appeared in Figure 1A wherein the red circles,meant to highlight differing areas of the two side-by-side UMAPs,were misaligned in the image.The corrected Figure 1,in which the red circles indicate areas of differing density within cluster#2,now appears both in the online article and below.The authors apologize for the confusion.

Single-nucleus RNA and ATAC sequencing reveals the impact of chromatin accessibility on gene expression in Arabidopsis roots at the singlecell level

Similar to other complex organisms,plants consist of diverse and specialized cell types.The gain of unique biological functions of these different cell types is the consequence of the establishment of cell-typespecific transcriptional programs.As a necessary step in gaining a deeper understanding of the regulatory mechanisms controlling plant gene expression,we report the use of single-nucleus RNA sequencing(sNucRNA-seq)and single-nucleus assay for transposase accessible chromatin sequencing(sNucATACseq)technologies on Arabidopsis roots.The comparison of our single-nucleus transcriptomes to the published protoplast transcriptomes validated the use of nuclei as biological entities to establish plant cell-type-specific transcriptomes.Furthermore,our sNucRNA-seq results uncovered the transcriptomes of additional cell subtypes not identified by single-cell RNA-seq.Similar to our transcriptomic approach,the sNucATAC-seq approach led to the distribution of the Arabidopsis nuclei into distinct clusters,suggesting the differential accessibility of chromatin between groups of cells according to their identity.To reveal the impact of chromatin accessibility on gene expression,we integrated sNucRNA-seq and sNucATAC-seq data and demonstrated that cell-type-specific marker genes display cell-type-specific patterns of chromatin accessibility.Our data suggest that the differential chromatin accessibility is a critical mechanism to regulate gene activity at the cell-type level.

Cell-specific pathways recruited for symbiotic nodulation in the Medicago truncatula legume

Medicago truncatula is a model legume species that has been studied for decades to understand the symbiotic relationship between legumes and soil bacteria collectively named rhizobia.This symbiosis called nodulation is initiated in roots with the infection of root hair cells by the bacteria,as well as the initiation of nodule primordia from root cortical,endodermal,and pericycle cells,leading to the development of a new root organ,the nodule,where bacteria fix and assimilate the atmospheric dinitrogen for the benefit of the plant.Here,we report the isolation and use of the nuclei from mock and rhizobia-inoculated roots for the single nuclei RNA-seq(sNucRNA-seq)profiling to gain a deeper understanding of early responses to rhizobial infection in Medicago roots.A gene expression map of the Medicago root was generated,comprising 25 clusters,which were annotated as specific cell types using 119 Medicago marker genes and orthologs to Arabidopsis cell-type marker genes.A focus on root hair,cortex,endodermis,and pericycle cell types,showing the strongest differential regulation in response to a short-term(48 h)rhizobium inoculation,revealed not only known genes and functional pathways,validating the sNucRNA-seq approach,but also numerous novel genes and pathways,allowing a comprehensive analysis of early root symbiotic responses at a cell type-specific level.