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Publications - Cell and Metabolic Biology

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Publications

Sheikh, A. H.; Fraz Hussain, R. M.; Tabassum, N.; Badmi, R.; Marillonnet, S.; Scheel, D.; Lee, J.; Sinha, A.; Possible role of WRKY transcription factors in regulating immunity in Oryza sativa ssp. indica Physiol. Mol. Plant Pathol. 114, 101623, (2021) DOI: 10.1016/j.pmpp.2021.101623

Plants have developed a robust transcription machinery to combat potential pathogenic organisms. One of the hallmarks of early immune responses is the activation of the WRKY transcription factors post infection. Specific WRKYs proteins from Arabidopsis are known substrates of MAPK pathway to mediate the flg22 elicited early immunity. In the current study, using the Golden Gate cloning strategy, we aim to clone the entire WRKY transcription factor family from Oryza sativa ssp. indica consisting of more than 100 members and study their MAPK interaction and subsequent role in PTI. Using a reporter LUC assay in protoplasts we investigated the early defense responses in a few interesting OsWRKY candidates. Interestingly, we observed stringent regulation of WRKY expression in cells and their transcriptional expression only under specific stress responses. The phenomenon of gene expression regulation by intron retention (IR) was prevalently observed in rice WRKY transcripts. We could show the role of WRKY8, 24, and 77 in early defense responses. It was observed that WRKY24 enhanced the expression of early defense response marker genes like NHL10 while WRKY8 and WRKY77 supressed their expression. This study highlights the complicated mechanism by which OsWRKYs expression is possibly regulated and the distinctive roles of some individual members in plant immunity. At the same time this study serves as a cautionary warning for plant researchers to be mindful of the intron retention mechanism while cloning OsWRKYs.
Publications

Tabassum, N.; Eschen-Lippold, L.; Athmer, B.; Baruah, M.; Brode, M.; Maldonado-Bonilla, L. D.; Hoehenwarter, W.; Hause, G.; Scheel, D.; Lee, J.; Phosphorylation‐dependent control of an RNA granule‐localized protein that fine‐tunes defence gene expression at a post‐transcriptional level Plant J. 101, 1023-1039, (2020) DOI: 10.1111/tpj.14573

Mitogen‐activated protein kinase (MAPK) cascades are key signalling modules of plant defence responses to pathogen‐associated molecular patterns (PAMPs, e.g. bacterial flg22 peptide). The Tandem Zinc Finger Protein 9 (TZF9) is an RNA‐binding protein that is phosphorylated by two PAMP‐responsive MAPKs, MPK3 and MPK6. We mapped the major phosphosites in TZF9 and showed their importance for controlling in vitro RNA‐binding activity, in vivo flg22‐induced rapid disappearance of TZF9‐labelled processing body‐like structures and TZF9 protein turnover. Microarray analysis showed a strong discordance between transcriptome (total mRNA) and translatome (polysome‐associated mRNA) in the tzf9 mutant, with more mRNAs associated to ribosomes in the absence of TZF9. This suggests that TZF9 may sequester and inhibit translation of subsets of mRNAs. Fittingly, TZF9 physically interacts with poly(A)‐binding protein 2 (PAB2), a hallmark constituent of stress granules – a site for stress‐induced translational stalling/arrest. TZF9 even promotes stress granule assembly in the absence of stress. Hence, MAPKs may control defence gene expression post‐transcriptionally through release from translation arrest within TZF9‐PAB2‐containing RNA granules or perturbing PAB2 functions in translation control (e.g. in the mRNA closed‐loop model of translation).
Publications

Blüher, D.; Laha, D.; Thieme, S.; Hofer, A.; Eschen-Lippold, L.; Masch, A.; Balcke, G.; Pavlovic, I.; Nagel, O.; Schonsky, A.; Hinkelmann, R.; Wörner, J.; Parvin, N.; Greiner, R.; Weber, S.; Tissier, A.; Schutkowski, M.; Lee, J.; Jessen, H.; Schaaf, G.; Bonas, U.; A 1-phytase type III effector interferes with plant hormone signaling Nat. Commun. 8, 2159, (2017) DOI: 10.1038/s41467-017-02195-8

Most Gram-negative phytopathogenic bacteria inject type III effector (T3E) proteins into plant cells to manipulate signaling pathways to the pathogen’s benefit. In resistant plants, specialized immune receptors recognize single T3Es or their biochemical activities, thus halting pathogen ingress. However, molecular function and mode of recognition for most T3Es remains elusive. Here, we show that the Xanthomonas T3E XopH possesses phytase activity, i.e., dephosphorylates phytate (myo-inositol-hexakisphosphate, InsP6), the major phosphate storage compound in plants, which is also involved in pathogen defense. A combination of biochemical approaches, including a new NMR-based method to discriminate inositol polyphosphate enantiomers, identifies XopH as a naturally occurring 1-phytase that dephosphorylates InsP6 at C1. Infection of Nicotiana benthamiana and pepper by Xanthomonas results in a XopH-dependent conversion of InsP6 to InsP5. 1-phytase activity is required for XopH-mediated immunity of plants carrying the Bs7 resistance gene, and for induction of jasmonate- and ethylene-responsive genes in N. benthamiana.
Publications

Varet, A.; Hause, B.; Hause, G.; Scheel, D.; Lee, J.; The Arabidopsis NHL3 Gene Encodes a Plasma Membrane Protein and Its Overexpression Correlates with Increased Resistance to Pseudomonas syringae pv. tomato DC3000 Plant Physiol. 132, 2023-2033, (2003) DOI: 10.1104/pp.103.020438

The Arabidopsis genome contains a family of NDR1/HIN1-like (NHL) genes that show homology to the nonrace-specific disease resistance (NDR1) and the tobacco (Nicotiana tabacum) harpin-induced (HIN1) genes. NHL3 is a pathogen-responsive member of this NHL gene family that is potentially involved in defense. In independent transgenic NHL3-overexpressing plant lines, a clear correlation between increased resistance to virulent Pseudomonas syringae pv. tomato DC3000 and enhanced NHL3 transcript levels was seen. These transgenic plants did not show enhanced pathogenesis-related gene expression or reactive oxygen species accumulation. Biochemical and localization experiments were performed to assist elucidation of how NHL3 may confer enhanced disease resistance. Gene constructs expressing amino-terminal c-myc-tagged or carboxyl-terminal hemagglutinin epitope (HA)-tagged NHL3 demonstrated membrane localization in transiently transformed tobacco leaves. Stable Arabidopsis transformants containing the NHL3-HA construct corroborated the findings observed in tobacco. The detected immunoreactive proteins were 10 kD larger than the calculated size and could be partially accounted for by the glycosylation state. However, the expected size was not attained with deglycosylation, suggesting possibly additional posttranslational modification. Detergent treatment, but not chemicals used to strip membrane-associated proteins, could displace the immunoreactive signal from microsomal fractions, showing that NHL3 is tightly membrane associated. Furthermore, immunofluorescence and immunogold labeling, coupled with two-phase partitioning techniques, revealed plasma membrane localization of NHL3-HA. This subcellular localization of NHL3 positions it at an initial contact site to pathogens and may be important in facilitating interception of pathogen-derived signals.
Publications

Lee, J.; Vogt, T.; Schmidt, J.; Parthier, B.; Löbler, M.; Methyljasmonate-induced accumulation of coumaroyl conjugates in barley leaf segments Phytochemistry 44, 589-592, (1997) DOI: 10.1016/S0031-9422(96)00562-6

The effect of methyljasmonate on the induction of phenolic components in barley leaf segments was investigated. RP-HPLC of methanol extracts showed that three compounds accumulate to high concentrations in response to methyljasmonate treatment. Two of them were identified as N-(E)-4-coumaroylputrescine and N-(E)-4-coumaroylagmatine by UV-spectroscopy and mass spectrometry.
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