This weeks Arabidopsis Research Roundup includes an audio description provided by Katja Graumann from the Oxford Brookes Plant Endomembrane Group. Katja is involved in two of this weeks papers, the first of which describes the biology of a novel set of Nuclear Envelope (NE) localised proteins whereas the second is a phylogenetic analysis of a range of known NE-localised proteins. Elsewhere David Salt (CPIB) is the corresponding author on work that investigates the plants response to sulphur while David Twell (Leicester) co-leads a study into regulatory events that occur during early male germline development. Finally Juriaan Ton (Sheffield) is a co-author on a study that looks at the role of NAD in the defence response.
Pawar V, Poulet A, Détourné G, Tatout C, Vanrobays E, Evans DE, Graumann K (2016) A novel family of plant nuclear envelope-associated proteins. J Exp Bot
This study is lead by David Evans and Katja Graumann from the Oxford Brookes Nuclear Envelope (NE) Group and describes a newly discovered family of proteins that are associated with the Nuclear Envelope (NE). These Nuclear Envelope-Associated Proteins (NEAPs) are ubiquitously expressed and localize to the NE through a predicted TM domain. A genetic analysis showed that NEAP proteins are necessary for correct nuclear morphology. They form homodimers and also interact with the SUN1 and SUN2 proteins that also reside at the NE. Interestingly the authors show that NEAP1 interacts with the putative transcription factor AtbZIP18, indicative of a role for these proteins in the regulation of gene expression.
Katja kindly takes a few minutes to provide an audio description of the work that went into this paper.
David Evans (Oxford Brookes) is the corresponding author of this UK-French collaboration that uses phylogenetic analysis to investigate the evolution of nuclear envelope proteins throughout higher plants. These include Sad1-Unc84 (SUN) domain, Klarsicht/Anc1/Syne homology (KASH) domain and Crowded Nuclei (CRWN) proteins. In general the number of SUN proteins is conserved throughout higher plants whilst the function of the KASH domain proteins appears to have extended through evolutionary time. Contrary to many historic reports, it has become clear that the plant inner nuclear membrane contains a lamin-like structure and although the proteins proposed to make up this structure in plants (CRWN, NEAPs and KAKU4) can be identified in most plant lineages, they are absent in other eukaryotes. This suggests the factors that maintain nuclear structure convergently evolved a mode of maintaining nuclear structure.
Huang XY, Chao DY, Koprivova A, Danku J, Wirtz M, Müller S, Sandoval FJ, Bauwe H, Roje S, Dilkes B, Hell R, Kopriva S, Salt DE (2016) Nuclear Localised MORE SULPHUR ACCUMULATION1 Epigenetically Regulates Sulphur Homeostasis in Arabidopsis thaliana. PLoS Genet. 12(9):e1006298
http://dx.doi.org/10.1371/journal.pgen.1006298 Open Access
Current GARNet Chair David Salt (then Aberdeen but recently moved to CPIB in Nottingham) leads this collaboration between UK, US and German researchers that identifies the MORE SULPHUR ACCUMULATION1 (MSA1) protein, which regulates sulphur homeostasis. MSA1 is nuclear localised, is required for S-adenosylmethionine (SAM) production and DNA methylation whilst is essential for the response to sulphur. Therefore the authors show that MSA1 appears to sit at an important control point as the plant responds to sulphur by regulating SAM biosynthesis and genome-wide DNA methylation.
Peters B, Casey J, Aidley J, Zohrab S, Borg M, Twell D, Brownfield L (2016) A cis-regulatory module in the transcription factor DUO1 promoter. Plant Physiol.
http://dx.doi.org/10.1104/pp.16.01192 Open Access
David Twell (University of Leicester) is a co-corresponding author with Lynette Brownfield from the University of Otago in New Zealand. They investigate the DUO POLLEN1 (DUO1) protein that is only expressed in the male germline following the first asymmetric division that segregates the germ cell lineages. Following generation of transgenic reporter lines the authors conclude that expression of the DUO1 gene is controlled at the transcriptional level and so identified a <100bp a cis-element termed the Regulatory region Of DUO1 (ROD1). The Arabidopsis ROD1 could replicate the germline expression pattern when introduced into Medicago and the authors subsequent show that this regulatory module likely has conserved function across dicots. Therefore as the ROD1 is necessary for the specification for the male germline across plant species, it represents one of the earliest regulatory checkpoints during sexual reproduction in dicots.
Pétriacq P, Ton J, Patrit O, Tcherkez GG, Gakiere B (2016) NAD acts as an integral regulator of multiple defense layers Plant Physiol
http://dx.doi.org/10.1104/pp.16.00780 Open Access
University of Sheffield group leader (and recent ARR audio contributor) Juriaan Ton is an author on this Franco-Australian study into the role of nicotinamide adenine dinucleotide (NAD) as a signalling molecule during the defence response. Previously NAD-overproducing nadC plants have been shown to be more resistant to Pseudomonas syringae and this study extends this analysis to show increased resistance to a broader set of pathogens. Increased NAD induces production of reactive oxygen species (ROS) independent of NADPH oxidase and light metabolism but dependent on mitochondrial respiration. Furthermore, NAD primes the physical aspects of the defence response by increasing callose deposition and pathogen-responsive cell death. Metabolic profiling reveals that the plant responds to NAD similarly to pathogen-associated molecular patterns (PAMPs) and may provide an alternant signalling pathway to enable the plant to responses to pathogen attack. Finally the authors discuss how this signalling crosstalk may define the defence response.