Arabidopsis HOOKLESS1 Regulates Responses to Pathogens and Abscisic Acid through Interaction with MED18 and Acetylation of <i>WRKY33</i> and <i>ABI5</i> Chromatin

Liao, Chao-Jan,Lai, Zhibing,Lee, Sanghun,Yun, Dae-Jin,Mengiste, Tesfaye American Society of Plant Biologists 2016 The Plant cell Vol.28 No.7

<P>Arabidopsis thaliana HOOKLESS1 (HLS1) encodes a putative histone acetyltransferase with known functions in seedling growth. Here, we show that HLS1 regulates plant responses to pathogens and abscisic acid (ABA) through histone acetylation at chromatin of target loci. The hls1 mutants show impaired responses to bacterial and fungal infection, accelerated senescence, and impaired responses to ABA. HLS1 modulates the expression of WRKY33 and ABA INSENSITIVE5 (ABI5), known regulators of pathogen and ABA responses, respectively, through direct association with these loci. Histone 3 acetylation (H3Ac), a positive mark of transcription, at WRKY33 and ABI5 requires HLS1 function. ABA treatment and pathogen infection enhance HLS1 recruitment and H3Ac at WRKY33. HLS1 associates with Mediator, a eukaryotic transcription coregulatory complex, through direct interaction with mediator subunit 18 (MED18), with which it shares multiple functions. HLS1 recruits MED18 to the WRKY33 promoter, boosting WKRY33 expression, suggesting the synergetic action of HLS1 and MED18. By contrast, MED18 recruitment to ABI5 and transcriptional activation are independent of HLS1. ABA-mediated priming of resistance to fungal infection was abrogated in hls1 and wrky33 mutants but correlated with ABA-induced HLS1 accumulation. In sum, HLS1 provides a regulatory node in pathogen and hormone response pathways through interaction with the Mediator complex and important transcription factors.</P>

Global Regulation of Plant Immunity by Histone Lysine Methyl Transferases

Lee, Sanghun,Fu, Fuyou,Xu, Siming,Lee, Sang Yeol,Yun, Dae-Jin,Mengiste, Tesfaye American Society of Plant Biologists 2016 The Plant cell Vol.28 No.7

<P>Posttranslational modification of histones modulates gene expression affecting diverse biological functions. We showed that the Arabidopsis thaliana histone methyl transferases SET DOMAIN GROUP8 (SDG8) and SDG25 regulate pep1-, flg22-, and effector-triggered immunity as well as systemic acquired resistance. Genome-wide basal and induced transcriptome changes regulated by SDG8 and/or SDG25 showed that two genes of the SDG-dependent transcriptome, CAROTENOID ISOMERASE2 (CCR2) and ECERIFERUM3 (CER3), were also required for plant immunity, establishing mechanisms in defense functions for SDG8 and SDG25. CCR2 catalyzes the biosynthesis of carotenoids, whereas CER3 is involved in the biosynthesis of cuticular wax. SDG8 and SDG25 affected distinct and overlapping global and locus-specific histone H3 lysine 4 (H3K4) and histone H3 lysine 36 (H3K36) methylations. Loss of immunity in sdg mutants was attributed to altered global and CCR2- and CER3-specific histone lysine methylation (HLM). Loss of immunity in sdg, ccr2, and cer3 mutants was also associated with diminished accumulation of lipids and loss of cuticle integrity. In addition, sdg8 and sdg25 mutants were impaired in H2B ubiquitination (H2Bubn) at CCR2, CER3, and H2Bubn regulated R gene, SNC1, revealing crosstalk between the two types of histone modifications. In summary, SDG8 and SDG25 contribute to plant immunity directly through HLM or indirectly through H2Bubn and by regulating expression of plant immunity genes, accumulation of lipids, biosynthesis of carotenoids, and maintenance of cuticle integrity.</P>

Tomato PEPR1 ORTHOLOG RECEPTOR-LIKE KINASE1 Regulates Responses to Systemin, Necrotrophic Fungi, and Insect Herbivory

Xu, Siming,Liao, Chao-Jan,Jaiswal, Namrata,Lee, Sanghun,Yun, Dae-Jin,Lee, Sang Yeol,Garvey, Michael,Kaplan, Ian,Mengiste, Tesfaye American Society of Plant Biologists 2018 The Plant cell Vol.30 No.9

<P>PORK1 is identified and characterized as a receptor-like kinase involved in tomato responses to the endogenous peptide systemin.</P><P>Endogenous peptides regulate plant immunity and growth. Systemin, a peptide specific to the Solanaceae, is known for its functions in plant responses to insect herbivory and pathogen infections. Here, we describe the identification of the tomato (<I>Solanum lycopersicum</I>) PEPR1/2 ORTHOLOG RECEPTOR-LIKE KINASE1 (PORK1) as the TOMATO PROTEIN KINASE1b (TPK1b) interacting protein and demonstrate its biological functions in systemin signaling and tomato immune responses. Tomato <I>PORK1</I> RNA interference (RNAi) plants with significantly reduced <I>PORK1</I> expression showed increased susceptibility to tobacco hornworm (<I>Manduca sexta</I>), reduced seedling growth sensitivity to the systemin peptide, and compromised systemin-mediated resistance to <I>Botrytis cinerea.</I> Systemin-induced expression of <I>Proteinase Inhibitor II</I> (<I>PI-II</I>), a classical marker for systemin signaling, was abrogated in <I>PORK1</I> RNAi plants. Similarly, in response to systemin and wounding, the expression of jasmonate pathway genes was attenuated in <I>PORK1</I> RNAi plants. TPK1b, a key regulator of tomato defense against <I>B. cinerea</I> and <I>M. sexta</I>, was phosphorylated by PORK1. Interestingly, wounding- and systemin-induced phosphorylation of TPK1b was attenuated when <I>PORK1</I> expression was suppressed. Our data suggest that resistance to <I>B. cinerea</I> and <I>M. sexta</I> is dependent on PORK1-mediated responses to systemin and subsequent phosphorylation of TPK1b. Altogether, PORK1 regulates tomato systemin, wounding, and immune responses.</P>

Epigenetic switch from repressive to permissive chromatin in response to cold stress

Park, Junghoon,Lim, Chae Jin,Shen, Mingzhe,Park, Hee Jin,Cha, Joon-Yung,Iniesto, Elisa,Rubio, Vicente,Mengiste, Tesfaye,Zhu, Jian-Kang,Bressan, Ray A.,Lee, Sang Yeol,Lee, Byeong-ha,Jin, Jing Bo,Pardo, National Academy of Sciences 2018 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.115 No.23

<▼1><P><B>Significance</B></P><P>Phenotypic adaptations of plants in response to changes in climate are well known to be mediated by molecular mechanisms, including activation or suppression of transcription factors that control target gene expression. However, the chromatin changes that are essential for the binding of transcription factors are much less understood. Gene derepression at the chromatin level is considered to be the starting point for gene transcription. We report a mechanism of gene derepression through which HOS15 promotes the degradation of histone deacetylase HD2C in a cold-dependent manner that correlates with increased levels of acetylated histones on <I>COR</I> gene chromatin. Moreover, HOS15 directly promotes <I>COR</I> gene transcription by association of CBF transcription factors with the “open” state of the target <I>COR</I> chromatin.</P></▼1><▼2><P>Switching from repressed to active status in chromatin regulation is part of the critical responses that plants deploy to survive in an ever-changing environment. We previously reported that HOS15, a WD40-repeat protein, is involved in histone deacetylation and cold tolerance in <I>Arabidopsis</I>. However, it remained unknown how HOS15 regulates cold responsive genes to affect cold tolerance. Here, we show that HOS15 interacts with histone deacetylase 2C (HD2C) and both proteins together associate with the promoters of cold-responsive <I>COR</I> genes, <I>COR15A</I> and <I>COR47</I>. Cold induced HD2C degradation is mediated by the CULLIN4 (CUL4)-based E3 ubiquitin ligase complex in which HOS15 acts as a substrate receptor. Interference with the association of HD2C and the <I>COR</I> gene promoters by HOS15 correlates with increased acetylation levels of histone H3. HOS15 also interacts with CBF transcription factors to modulate cold-induced binding to the <I>COR</I> gene promoters. Our results here demonstrate that cold induces HOS15-mediated chromatin modifications by degrading HD2C. This switches the chromatin structure status and facilitates recruitment of CBFs to the <I>COR</I> gene promoters. This is an apparent requirement to acquire cold tolerance.</P></▼2>

Pathogen Associated Molecular Pattern (PAMP)- Triggered Immunity Is Compromised under C-Limited Growth

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.

CYCLIN-DEPENDENT KINASE8 Differentially Regulates Plant Immunity to Fungal Pathogens through Kinase-Dependent and -Independent Functions in <i>Arabidopsis</i>

Zhu, Yingfang,Schluttenhoffer, Craig M.,Wang, Pengcheng,Fu, Fuyou,Thimmapuram, Jyothi,Zhu, Jian-Kang,Lee, Sang Yeol,Yun, Dae-Jin,Mengiste, Tesfaye American Society of Plant Biologists 2014 The Plant cell Vol.26 No.10

<P>This work explores the intriguing roles of Mediator subunit CYCLIN-DEPENDENT KINASE8 (CDK8) in plant immune responses to fungal infection. CDK8 regulates jasmonate-responsive gene expression and cuticle development via interactions with MEDIATOR COMPLEX SUBUNIT25 and transcription factor WIN1, respectively, while other interactions suggest evolutionary conservation of the Mediator kinase module.</P><P>CYCLIN-DEPENDENT KINASE8 (CDK8) is a widely studied component of eukaryotic Mediator complexes. However, the biological and molecular functions of plant CDK8 are not well understood. Here, we provide evidence for regulatory functions of <I>Arabidopsis thaliana</I> CDK8 in defense and demonstrate its functional and molecular interactions with other Mediator and non-Mediator subunits. The <I>cdk8</I> mutant exhibits enhanced resistance to <I>Botrytis cinerea</I> but susceptibility to <I>Alternaria brassicicola</I>. The contributions of CDK8 to the transcriptional activation of defensin gene <I>PDF1.2</I> and its interaction with MEDIATOR COMPLEX SUBUNIT25 (MED25) implicate CDK8 in jasmonate-mediated defense. Moreover, CDK8 associates with the promoter of <I>AGMATINE COUMAROYLTRANSFERASE</I> to promote its transcription and regulate the biosynthesis of the defense-active secondary metabolites hydroxycinnamic acid amides. CDK8 also interacts with the transcription factor WAX INDUCER1, implying its additional role in cuticle development. In addition, overlapping functions of CDK8 with MED12 and MED13 and interactions between CDK8 and C-type cyclins suggest the conserved configuration of the plant Mediator kinase module. In summary, while CDK8’s positive transcriptional regulation of target genes and its phosphorylation activities underpin its defense functions, the impaired defense responses in the mutant are masked by its altered cuticle, resulting in specific resistance to <I>B. cinerea</I>.</P>

Limited Addition of the 6-Arm β1,2-linked <i>N</i>-Acetylglucosamine (GlcNAc) Residue Facilitates the Formation of the Largest <i>N</i>-Glycan in Plants

Yoo, Jae Yong,Ko, Ki Seong,Seo, Hyun-Kyeong,Park, Seongha,Fanata, Wahyu Indra Duwi,Harmoko, Rikno,Ramasamy, Nirmal Kumar,Thulasinathan, Thiyagarajan,Mengiste, Tesfaye,Lim, Jae-Min,Lee, Sang Yeol,Lee, American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.27

<P>The most abundant <I>N</I>-glycan in plants is the paucimannosidic <I>N</I>-glycan with core β1,2-xylose and α1,3-fucose residues (Man<SUB>3</SUB>XylFuc(GlcNAc)<SUB>2</SUB>). Here, we report a mechanism in <I>Arabidopsis thaliana</I> that efficiently produces the largest <I>N</I>-glycan in plants. Genetic and biochemical evidence indicates that the addition of the 6-arm β1,2-GlcNAc residue by <I>N</I>-acetylglucosaminyltransferase II (GnTII) is less effective than additions of the core β1,2-xylose and α1,3-fucose residues by XylT, FucTA, and FucTB in <I>Arabidopsis</I>. Furthermore, analysis of <I>gnt2</I> mutant and 35S:GnTII transgenic plants shows that the addition of the 6-arm non-reducing GlcNAc residue to the common <I>N</I>-glycan acceptor GlcNAcMan<SUB>3</SUB>(GlcNAc)<SUB>2</SUB> inhibits additions of the core β1,2-xylose and α1,3-fucose residues. Our findings indicate that plants limit the rate of the addition of the 6-arm GlcNAc residue to the common <I>N</I>-glycan acceptor as a mechanism to facilitate formation of the prevalent <I>N</I>-glycans with Man<SUB>3</SUB>XylFuc(GlcNAc)<SUB>2</SUB> and (GlcNAc)<SUB>2</SUB>Man<SUB>3</SUB>XylFuc(GlcNAc)<SUB>2</SUB> structures.</P>

Pathogen Associated Molecular Pattern (PAMP)-Triggered Immunity Is Compromised under C-Limited Growth

Park, Hyeong Cheol,Lee, Shinyoung,Park, Bokyung,Choi, Wonkyun,Kim, Chanmin,Lee, Sanghun,Chung, Woo Sik,Lee, Sang Yeol,Sabir, Jamal,Bressan, Ray A.,Bohnert, Hans J.,Mengiste, Tesfaye,Yun, Dae-Jin Korean Society for Molecular and Cellular Biology 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 period-dependent 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.