Unknown,Transcriptomics,Genomics,Proteomics

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RNA-Seq of single cells from regenerating Arabidopsis root

ABSTRACT: Plant roots can regenerate after complete excision of their tip, including the stem cell niche, but it is not clear what developmental program mediates such repair. Here, we use a combination of lineage tracing, single-cell RNA-seq, and marker analysis to test different models of tissue reassembly. We show that rapid cell-identity transitions lead to the formation of a new stem cell niche from multiple remnant tissues. The transcriptome of regenerating cells prior to stem cell activation resembled that of the embryonic root progenitor, and regeneration defects were more severe in embryonic versus adult root mutants. Furthermore, the signaling domains of the hormones auxin and cytokinin mirrored their embryonic dynamics, and manipulation of both hormones altered the position of new tissues and stem cell niche markers. Our findings suggest that plant organ regeneration resembles the developmental stages of embryonic patterning and is guided by spatial information laid down by complementary hormone domains. 215 single cells isolated from marked stele tissue (either using WOL or AHP6 promoters), before, at 3h, 16h and 46h post root tip decapitation

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Idan Efroni

PROVIDER: E-GEOD-74488 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Aluminum (Al) toxicity and phosphate (Pi) limitation are widespread chronic abiotic and mutually enhancing stresses that profoundly affect crop yield. Both stresses causes a strong inhibition of root growth due to a progressive exhaustion of the stem cell niche. Here we report on a CASEIN KINASE 2 (CK2) inhibitor identified by its capability to maintain a functional root stem cell niche under Al toxic conditions. CK2 operates through phosphorylation of the cell cycle checkpoint activator SUPPRESSOR OF GAMMA RADIATION 1 (SOG1), priming its activity under DNA damaging conditions. In addition to yielding Al tolerance, both CK2 and SOG1 inactivation result in resistance to phosphate starvation, revealing the existence of a low phosphate induced cell cycle checkpoint that depends on the DNA damage activator ATAXIA-TELANGIECTASIA MUTATED (ATM). Overall, our data reveal an important physiological role for the plant DNA damage response pathway under agricultural limiting growth conditions and opening new avenues to cope with the problem of Pi limitation. SOG1 can be phosphorylated by both ATM and ATR (Sjogren et al., 2015; Yoshiyama et al., 2017). ATM phosphorylation of SOG1 can occur at five different S/TQ sites upon treatment with double-stand break inducing compounds such as zeocin. This phosphorylation is important for its activity, as demonstrated by the inability of a phosphor-mutant allele to complement the sog1 mutant. In addition to the ATM/ATR-dependent phosphorylation sites, 11 putative CK2 phosphorylation sites [T/SXXE/D, with S or T serving as the phospho-acceptor site (Meggio and Pinna, 2003)] are found within the full length SOG1 proteins. Among these, four sites are conserved among orthologous proteins, stressing their potential importance to protein function. Of these, three cluster at the extreme C-terminus of SOG1, which also is also the location of the ATM/ATR phosphorylation sites. To test putative phosphorylation of any of these sites, TAP-tagged SOG1 protein was extracted and purified from cell cultures and subjected to phosphorylation analysis.

Project description:This model is from the article: The influence of cytokinin-auxin cross-regulation on cell-fate determination in Arabidopsis thaliana root development Muraro D, Byrne H, King J, Voss U, Kieber J, Bennett M. J Theor Biol.2011 Aug 21;283(1):152-67. PMID: 21640126, Abstract: Root growth and development in Arabidopsis thaliana are sustained by a specialised zone termed the meristem, which contains a population of dividing and differentiating cells that are functionally analogous to a stem cell niche in animals. The hormones auxin and cytokinin control meristem size antagonistically. Local accumulation of auxin promotes cell division and the initiation of a lateral root primordium. By contrast, high cytokinin concentrations disrupt the regular pattern of divisions that characterises lateral root development, and promote differentiation. The way in which the hormones interact is controlled by a genetic regulatory network. In this paper, we propose a deterministic mathematical model to describe this network and present model simulations that reproduce the experimentally observed effects of cytokinin on the expression of auxin regulated genes. We show how auxin response genes and auxin efflux transporters may be affected by the presence of cytokinin. We also analyse and compare the responses of the hormones auxin and cytokinin to changes in their supply with the responses obtained by genetic mutations of SHY2, which encodes a protein that plays a key role in balancing cytokinin and auxin regulation of meristem size. We show that although shy2 mutations can qualitatively reproduce the effect of varying auxin and cytokinin supply on their response genes, some elements of the network respond differently to changes in hormonal supply and to genetic mutations, implying a different, general response of the network. We conclude that an analysis based on the ratio between these two hormones may be misleading and that a mathematical model can serve as a useful tool for stimulate further experimental work by predicting the response of the network to changes in hormone levels and to other genetic mutations.

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RNA-Seq of single cells from regenerating Arabidopsis root

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