Sensory plastids are important in plant responses to environmental changes. Previous studies show that
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SUMMARY MutS HOMOLOG 1 (MSH1 ) perturbation in sensory plastids induces heritable epigenetic phenotype adjustment. Previously, the PsbP homolog DOMAIN‐CONTAINING PROTEIN 3 (PPD3), a protein of unknown function, was postulated to be an interactor with MSH1. This study investigates the relationship of PPD3 with MSH1 and with plant environmental sensing. Theppd3 mutant displays a whole‐plant phenotype variably altered in growth rate, flowering time, reactive oxygen species (ROS) modulation and response to salt, with effects on meristem growth. Present in both chloroplasts and sensory plastids, PPD3 colocalized with MSH1 in root tips but not in leaf tissues. The suppression or overexpression of PPD3 affected the plant growth rate and stress tolerance, and led to a heritable, heterogenous ‘memory’ state with both dwarfed and vigorous growth phenotypes. Gene expression and DNA methylome data sets from PPD3‐OX and derived memory states showed enrichment in growth versus defense networks and meristem effects. Our results support a model of sensory plastid influence on nuclear epigenetic behavior andppd3 as a second trigger, functioning within meristem plastids to recalibrate growth plasticity. -
Søgaard-Andersen, Lotte (Ed.)ABSTRACT Precise control of the cell cycle is central to the physiology of all cells. In prior work we demonstrated that archaeal cells maintain a constant size; however, the regulatory mechanisms underlying the cell cycle remain unexplored in this domain of life. Here, we use genetics, functional genomics, and quantitative imaging to identify and characterize the novel CdrSL gene regulatory network in a model species of archaea. We demonstrate the central role of these ribbon-helix-helix family transcription factors in the regulation of cell division through specific transcriptional control of the gene encoding FtsZ2, a putative tubulin homolog. Using time-lapse fluorescence microscopy in live cells cultivated in microfluidics devices, we further demonstrate that FtsZ2 is required for cell division but not elongation. The cdrS-ftsZ2 locus is highly conserved throughout the archaeal domain, and the central function of CdrS in regulating cell division is conserved across hypersaline adapted archaea. We propose that the CdrSL-FtsZ2 transcriptional network coordinates cell division timing with cell growth in archaea. IMPORTANCE Healthy cell growth and division are critical for individual organism survival and species long-term viability. However, it remains unknown how cells of the domain Archaea maintain a healthy cell cycle. Understanding the archaeal cell cycle is of paramount evolutionary importance given that an archaeal cell was the host of the endosymbiotic event that gave rise to eukaryotes. Here, we identify and characterize novel molecular players needed for regulating cell division in archaea. These molecules dictate the timing of cell septation but are dispensable for growth between divisions. Timing is accomplished through transcriptional control of the cell division ring. Our results shed light on mechanisms underlying the archaeal cell cycle, which has thus far remained elusive.more » « less
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Summary The
NLR ‐receptorRPP 7 mediates race‐specific immunity in Arabidopsis. Previous screens forenhanced downy mildew (edm ) mutants identified the co‐chaperoneSGT 1b (EDM 1) and thePHD ‐finger proteinEDM 2 as critical regulators ofRPP 7. Here, we describe a thirdedm mutant compromised inRPP 7edm3 .EDM 3RNA ‐recognition motif. LikeEDM 2,EDM 3 promotes histone H3 lysine 9 dimethylation (H3K9me2) atRPP 7EDM 3 to affect this silencing mark at a large set of loci. Importantly, bothEDM 3 andEDM 2 co‐associatein vivo with H3K9me2‐marked chromatin and transcripts at a critical proximal polyadenylation site ofRPP 7NLR gene regulation, and establish a functional and physical link between a histone mark andNLR ‐transcript processing.
