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Ubiquitin and Ubiquitin-like Modifiers in Plants
Park, Hee-Jin,Park, Hyeong-Cheol,Lee, Sang-Yeol,Bohnert, Hans J.,Yun, Dae-Jin 한국식물학회 2011 Journal of Plant Biology Vol.54 No.5
Posttranslational modifications of proteins by small polypeptides including ubiquitination, neddylation (related to ubiquitin (RUB) conjugation), and sumoylation are implicated in plant growth and development, and they regulate protein degradation, location, and interaction with other proteins. Ubiquitination mediates the selective degradation of proteins by the ubiquitin (Ub)/proteasome pathway. The ubiquitin-like protein RUB is conjugated to cullins, which are part of a ubiquitin E3 ligase complex that is involved in auxin hormonal signaling. Sumoylation, by contrast, is known for its involvement in guiding protein interactions related to abiotic and biotic stresses and in the regulation of flowering time. ATG8/ATG12-mediated autophagy influences degradation and recycling of cellular components. Other ubiquitin-like modifiers (ULPs) such as homology to Ub-1, ubiquitin-fold modifier 1, and membrane-anchored Ub-fold are also found in Arabidopsis. ULPs share similar three-dimensional structures and a conjugation system, including E1 activating enzymes, E2 conjugation enzymes, and E3 ligases, as well as proteases for deconjugation and recycling of the tags. However, each of the ULP posttranslational modifications possesses its own specific enzymes and modifies its specific targets selectively. This review discusses recent findings on ubiquitination and ubiquitin-like modifier processes and their roles in the posttranslational modification of proteins in Arabidopsis.
Wegner Alex,Casanova Florencia,Loehrer Marco,Jordine Angelina,Bohnert Stefan,Liu Xinyu,Zhang Zhengguang,Schaffrath Ulrich 한국미생물학회 2022 The journal of microbiology Vol.60 No.1
Phytopathogenic fungi are known to secrete specific proteins which act as virulence factors and promote host colonization. Some of them are enzymes with plant cell wall degradation capability, like pectate lyases (Pls). In this work, we examined the involvement of Pls in the infection process of Magnaporthe oryzae, the causal agent of rice blast disease. From three Plgenes annotated in the M. oryzae genome, only transcripts of MoPL1 considerably accumulated during the infection process with a peak at 72 h post inoculation. Both, gene deletion and a constitutive expression of MoPL1 in M. oryzae led to a significant reduction in virulence. By contrast, mutants that constitutively expressed an enzymatic inactive version of MoPl1 did not differ in virulence compared to the wild type isolate. This indicates that the enzymatic activity of MoPl1 is responsible for diminished virulence, which is presumably due to degradation products recognized as danger associated molecular patterns (DAMPs), which strengthen the plant immune response. Microscopic analysis of infection sites pointed to an increased plant defense response. Additionally, MoPl1 tagged with mRFP, and not the enzymatic inactive version, focally accumulated in attacked plant cells beneath appressoria and at sites where fungal hyphae transverse from one to another cell. These findings shed new light on the role of pectate lyases during tissue colonization in the necrotrophic stage of M. oryzae's life cycle.
Intracellular consequences of SOS1 deficiency during salt stress
Oh, Dong-Ha,Lee, Sang Yeol,Bressan, Ray A.,Yun, Dae-Jin,Bohnert, Hans J. Oxford University Press 2010 Journal of experimental botany Vol.61 No.4
<P>A mutation of AtSOS1 (Salt Overly Sensitive 1), a plasma membrane Na<SUP>+</SUP>/H<SUP>+</SUP>-antiporter in <I>Arabidopsis thaliana,</I> leads to a salt-sensitive phenotype accompanied by the death of root cells under salt stress. Intracellular events and changes in gene expression were compared during a non-lethal salt stress between the wild type and a representative SOS1 mutant, <I>atsos1-1,</I> by confocal microscopy using ion-specific fluorophores and by quantitative RT-PCR. In addition to the higher accumulation of sodium ions, <I>atsos1-1</I> showed inhibition of endocytosis, abnormalities in vacuolar shape and function, and changes in intracellular pH compared to the wild type in root tip cells under stress. Quantitative RT-PCR revealed a dramatically faster and higher induction of root-specific Ca<SUP>2+</SUP> transporters, including several CAXs and CNGCs, and the drastic down-regulation of genes involved in pH-homeostasis and membrane potential maintenance. Differential regulation of genes for functions in intracellular protein trafficking in <I>atsos1-1</I> was also observed. The results suggested roles of the SOS1 protein, in addition to its function as a Na<SUP>+</SUP>/H<SUP>+</SUP> antiporter, whose disruption affected membrane traffic and vacuolar functions possibly by controlling pH homeostasis in root cells.</P>
Involvement of Arabidopsis HOS15 in histone deacetylation and cold tolerance.
Zhu, Jianhua,Jeong, Jae Cheol,Zhu, Yanmei,Sokolchik, Irina,Miyazaki, Saori,Zhu, Jian-Kang,Hasegawa, Paul M,Bohnert, Hans J,Shi, Huazhong,Yun, Dae-Jin,Bressan, Ray A National Academy of Sciences 2008 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.105 No.12
<P>Histone modification in chromatin is one of the key control points in gene regulation in eukaryotic cells. Protein complexes composed of histone acetyltransferase or deacetylase, WD40 repeat protein, and many other components have been implicated in this process. Here, we report the identification and functional characterization of HOS15, a WD40-repeat protein crucial for repression of genes associated with abiotic stress tolerance through histone deacetylation in Arabidopsis. HOS15 shares high sequence similarity with human transducin-beta like protein (TBL), a component of a repressor protein complex involved in histone deacetylation. Mutation of the HOS15 gene renders mutant plants hypersensitive to freezing temperatures. HOS15 is localized in the nucleus and specifically interacts with histone H4. The level of acetylated histone H4 is higher in the hos15 mutant than in WT plants. Moreover, the stress inducible RD29A promoter is hyperinduced and associated with a substantially higher level of acetylated histone H4 in the hos15 mutant under cold stress conditions. Our results suggest a critical role for gene activation/repression by histone acetylation/deacetylation in plant acclimation and tolerance to cold stress.</P>
박형철,Xuan Canh Nguyen,Sunghwa Bahk,Byung Ouk Park,김호수,Min-Chul Kim,Hans J. Bohnert,정우식 한국식물생명공학회 2016 Plant biotechnology reports Vol.10 No.6
Phosphorylation of substrate proteins by mitogen-activated protein kinases (MPKs) determines the specific cellular responses elicited by a particular extracellular stimulus. However, downstream targets of plant MPKs remain poorly characterized. In this study, 29 putative substrates of AtMPK3, AtMPK4 and AtMPK6 were identified by solid-phase phosphorylation screening of a k phage expression library constructed from combined mRNAs from salt-treated, pathogen-treated and mechanically wounded Arabidopsis seedlings. To test the efficiency of this screening, we performed in vitro kinase assay with 10 recombinant fusion proteins. All proteins were phosphorylated by AtMPK3, AtMPK4 and AtMPK6, indicating the efficiency of this screening procedure. To confirm phosphorylation of isolated substrates by plant MPKs, we performed in-gel kinase assays. All test substrates were strongly phosphorylated by wounding or H2O2-activated AtMPK3 and AtMPK6. Three substrates, encoded by genes At2g41430, At2g41900, and At3g16770, were strongly phosphorylated, suggesting a function as AtMPK substrates. The type of screening provides a powerful way for identifying potential substrates of MAP kinases responsive to biotic and abiotic stresses.
박형철,이신영,박보경,최원규,김찬민,Sanghun Lee,정우식,이상열,Jamal Sabir,Ray A. Bressan,Hans J. Bohnert,Tesfaye Mengiste,윤대진 한국분자세포생물학회 2015 Molecules and cells Vol.38 No.1
In the interaction between plants and pathogens, carbon (C) resources provide energy and C skeletons to maintain, among many functions, the plant immune system. However, variations in C availability on pathogen associated molecular pattern (PAMP) triggered immunity (PTI) have not been systematically examined. Here, three types of starch mutants with enhanced susceptibility to Pseudomonas syringae pv. tomato DC3000 hrcC were examined for PTI. In a dark perioddependent manner, the mutants showed compromised induction of a PTI marker, and callose accumulation in response to the bacterial PAMP flagellin, flg22. In combination with weakened PTI responses in wild type by inhibition of the TCA cycle, the experiments determined the necessity of C-derived energy in establishing PTI. Global gene expression analyses identified flg22 responsive genes displaying C supply-dependent patterns. Nutrient recycling-related genes were regulated similarly by C-limitation and flg22, indicating re-arrangements of expression programs to redirect resources that establish or strengthen PTI. Ethylene and NAC transcription factors appear to play roles in these processes. Under C-limitation, PTI appears compromised based on suppression of genes required for continued biosynthetic capacity and defenses through flg22. Our results provide a foundation for the intuitive perception of the interplay between plant nutrition status and pathogen defense.
Bressan, Ray A.,Park, Hyeong Cheol,Orsini, Francesco,Oh, Dong-Ha,Dassanayake, Maheshi,Inan, Gunsu,Yun, Dae-Jin,Bohnert, Hans J.,Maggio, Albino 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.1
Molecular genetics has confirmed older research and generated new insights into the ways how plants deal with adverse conditions. This body of research is now being used to interpret stress behavior of plants in new ways, and to add results from most recent genomicsbased studies. The new knowledge now includes genome sequences of species that show extreme abiotic stress tolerances, which enables new strategies for applications through either molecular breeding or transgenic engineering. We will highlight some physiological features of the extremophile lifestyle, outline emerging features about halophytism based on genomics, and discuss conclusions about underlying mechanisms.