Project description:Plant defense responses involve several biological processes that allow plants to fight against pathogenic attacks. How these different processes are orchestrated within organs and depend on specific cell types is poorly known. Here, using single-cell RNA sequencing (scRNA-seq) technology on three independent biological replicates, we identified several cell populations representing the core transcriptional responses of wild-type Arabidopsis leaves inoculated with the bacterial pathogen Pseudomonas syringae DC3000. Among these populations, we retrieved major cell types of the leaves (mesophyll, guard, epidermal, companion, and vascular S cells) with which we could associate characteristic transcriptional reprogramming and regulators, thereby specifying different cell-type responses to the pathogen. Further analyses of transcriptional dynamics, on the basis of inference of cell trajectories, indicated that the different cell types, in addition to their characteristic defense responses, can also share similar modules of gene reprogramming, uncovering a ubiquitous antagonism between immune and susceptible processes. Moreover, it appears that the defense responses of vascular S cells, epidermal cells, and mesophyll cells can evolve along two separate paths, one converging toward an identical cell fate, characterized mostly by lignification and detoxification functions. As this divergence does not correspond to the differentiation between immune and susceptible cells, we speculate that this might reflect the discrimination between cell-autonomous and non-cell-autonomous responses. Altogether our data provide an upgraded framework to describe, explore, and explain the specialization and the coordination of plant cell responses upon pathogenic challenge.
Project description:Polyethilenimine (PEI) functionalized single walled carbon nanotubes (SWNTs) and carbon-based nanomaterials enable delivery of DNA and RNA in plants. Given the broad-scale use of PEI-functionalized nanomaterials in plants, we sought to investigate the reaction of plant tissues to treatment with PEI-SWNTs and pristine SWNTs. To this end, we infiltrated Arabidopsis thaliana leaves with pristine single walled carbon nanotubes used in RNA silencing applications (SWNTs) and polyethyleneimine-functionalized SWNTs used for plasmid DNA delivery (PEI-SWNTs). We used Arabidopsis as it is a well characterized model plant, for which genomic and detailed gene function information is readily available. To minimize the effects caused by the introduction of exogenous nucleic acids, in SWNT preparations we used single stranded RNA targeting Green Fluorescent Protein (GFP) with no target sequence in the Arabidopsis genome, and a plasmid that expresses GFP in PEI-SWNT preparations. For our experiments herein, we used ~25-50 fold higher concentrations of SWNTs and PEI-SWNTs compared to standard concentrations used in biomolecule delivery assays. Water-infiltrated plant leaves served as a negative control to distinguish between the SWNT-specific response and the response to the infiltration process itself. We performed RNA sequencing (RNA-seq) with RNA extracted from leaves two days after infiltration to identify changes in the leaf transcriptomic profile in response to the three treatments, compared to non-infiltrated leaves.
Project description:Transcriptional profiling of Arabidopsis thaliana, comparing control wild-type (ecotype Wassilewskija, Ws) leaves with leaves from transgenic plants overexpressing the transcription factor RAP2.6L under control of the cauliflower mosaic virus 35S promoter (RAP2.6L-OX; this line was originally described in Krishnaswamy et al (2010)).
Project description:Leaves are flat determinate organs derived from indeterminate shoot apical meristems. The presence of a specific leaf meristem is debated, as anatomical features typical of meristems are not present in leaves. Here we demonstrate that multiple NGATHA (NGA) and CINCINNATA-class-TCP (CIN-TCP) transcription factors act redundantly to suppress activity of a leaf margin meristem in Arabidopsis thaliana, and that their absence confers persistent marginal growth of leaves, cotyledons and floral organs. The marginal meristem is activated by the juxtaposition of adaxial and abaxial domains and maintained by WOX homeobox transcription factors, but other margin elaboration genes are dispensable for its maintenance. This genetic framework parallels the morphogenetic program of shoot apical meristems and may represent a relic from an ancestral shoot system from which seed plant leaves evolved.
Project description:We profiled small RNAs obtained from B. cinerea-infected Arabidopsis rosette leaves at four different time points after inoculation.
Project description:Brevicompanines are natural products isolated from the culture filtrate of the fungus Penicillium brevicompactum. They showed plant growth regulating properties in several species including lettuce, rice or Arabidopsis thaliana. We used microarrays to gather information about the reprogramming of gene transcription when Arabidopsis leaves were treated with Brevicompanine C (BrvC) that showed significant activity in plant growth assays.