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Glutathione transferase U13 functions in pathogen-triggered glucosinolate metabolism

Glutathione transferase U13 functions in pathogen-triggered glucosinolate metabolism | My publications | Scoop.it
Glutathione (GSH) and indole glucosinolates (IGs) exert key functions in the immune system of the model plant Arabidopsis thaliana. Appropriate GSH levels are important for execution of both pre- and post-invasive disease resistance mechanisms to invasive pathogens, while an intact PENETRATION2 (PEN2)-pathway for IG-metabolism is essential for pre-invasive resistance in this species. Earlier indirect evidence suggested that the latter pathway involves conjugation of GSH with unstable products of IG metabolism and further processing of the resulting adducts to biologically active molecules. Here we describe the identification of Glutahione-S-Transferase class-tau member 13 (GSTU13) as an indispensable component of the PEN2 immune pathway for IG metabolism. gstu13 mutant plants are defective in the pathogen-triggered biosynthesis of end products of the PEN2 pathway, including 4-O-β-D-glucosyl-indol-3-yl formamide, indole-3-ylmethyl amine and raphanusamic acid. In line with this metabolic defect, lack of functional GSTU13 results in enhanced disease susceptibility towards several fungal pathogens including Erysiphe pisi, Colletotrichum gloeosporioides and Plectosphaerella cucumerina. Seedlings of gstu13 plants fail also to deposit the (1,3)-β-glucan cell wall polymer, callose, after recognition of the bacterial flg22 epitope. We show that GSTU13 mediates specifically the role of GSH in IG-metabolism without noticeable impact on other immune functions of this tripeptide. We postulate that GSTU13 connects GSH with the pathogen-triggered PEN2 pathway for IG metabolism to deliver metabolites that may have numerous functions in the innate immune system of A. thaliana.
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Root Endophyte Colletotrichum tofieldiae Confers Plant Fitness Benefits that Are Phosphate Status Dependent: Cell

Root Endophyte Colletotrichum tofieldiae Confers Plant Fitness Benefits that Are Phosphate Status Dependent: Cell | My publications | Scoop.it
Highlights
•Colletotrichum tofieldiae (Ct) is a fungal root endophyte of Arabidopsis
•Ct transfers the macronutrient phosphorus to Arabidopsis shoots
•Ct-mediated plant growth promotion needs an intact phosphate starvation response
•A branch of the plant innate immune system is essential for beneficial Ct activities
Summary
A staggering diversity of endophytic fungi associate with healthy plants in nature, but it is usually unclear whether these represent stochastic encounters or provide host fitness benefits. Although most characterized species of the fungal genus Colletotrichum are destructive pathogens, we show here that C. tofieldiae (Ct) is an endemic endophyte in natural Arabidopsis thaliana populations in central Spain. Colonization by Ct initiates in roots but can also spread systemically into shoots. Ct transfers the macronutrient phosphorus to shoots, promotes plant growth, and increases fertility only under phosphorus-deficient conditions, a nutrient status that might have facilitated the transition from pathogenic to beneficial lifestyles. The host’s phosphate starvation response (PSR) system controls Ct root colonization and is needed for plant growth promotion (PGP). PGP also requires PEN2-dependent indole glucosinolate metabolism, a component of innate immune responses, indicating a functional link between innate immunity and the PSR system during beneficial interactions with Ct.
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PLOS ONE: ERMO3/MVP1/GOLD36 Is Involved in a Cell Type-Specific Mechanism for Maintaining ER Morphology in Arabidopsis thaliana

PLOS ONE: ERMO3/MVP1/GOLD36 Is Involved in a Cell Type-Specific Mechanism for Maintaining ER Morphology in Arabidopsis thaliana | My publications | Scoop.it

The endoplasmic reticulum (ER) has a unique, network-like morphology. The ER structures are composed of tubules, cisternae, and three-way junctions. This morphology is highly conserved among eukaryotes, but the molecular mechanism that maintains ER morphology has not yet been elucidated. In addition, certain Brassicaceae plants develop a unique ER-derived organelle called the ER body. This organelle accumulates large amounts of PYK10, a β-glucosidase, but its physiological functions are still obscure. We aimed to identify a novel factor required for maintaining the morphology of the ER, including ER bodies, and employed a forward-genetic approach using transgenic Arabidopsis thaliana (GFP-h) with fluorescently-labeled ER. We isolated and investigated a mutant (designated endoplasmic reticulum morphology3, ermo3) with huge aggregates and abnormal punctate structures of ER. ERMO3encodes a GDSL-lipase/esterase family protein, also known as MVP1. Here, we showed that, although ERMO3/MVP1/GOLD36 was expressed ubiquitously, the morphological defects ofermo3 were specifically seen in a certain type of cells where ER bodies developed. Coimmunoprecipitation analysis combined with mass spectrometry revealed that ERMO3/MVP1/GOLD36 interacts with the PYK10 complex, a huge protein complex that is thought to be important for ER body-related defense systems. We also found that the depletion of transcription factor NAI1, a master regulator for ER body formation, suppressed the formation of ER-aggregates in ermo3 cells, suggesting that NAI1 expression plays an important role in the abnormal aggregation of ER. Our results suggest that ERMO3/MVP1/GOLD36 is required for preventing ER and other organelles from abnormal aggregation and for maintaining proper ER morphology in a coordinated manner with NAI1.

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Amazon.co.jp: Photobook植物細胞の知られざる世

Amazon.co.jp: Photobook植物細胞の知られざる世界: 永野 惇, 桧垣 匠, 三村 徹郎, 西村 いくこ, 西村 幹夫, 真野 昌二: 本
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Plant and Cell Physiol: Quantitative Analysis of ER Body Morphology in an Arabidopsis Mutant

Plant and Cell Physiol: Quantitative Analysis of ER Body Morphology in an Arabidopsis Mutant | My publications | Scoop.it

Although fluorescence microscopy screening has proven useful in the identification of genes involved in plant organelle biogenesis and integrity, the quantitative and statistical study of the geometric phenotype is highly limited. This situation could generate unconscious bias in the understanding and presentation of a mutant phenotype. Therefore, we have developed an automated quantification system for green fluorescent protein (GFP) images, which enabled us to easily obtain quantitative data on ER bodies (an endoplasmic reticulum-derived organelle). We isolated an ER body morphology mutant of Arabidopsis thaliana, leb-1 (long ER body). The leb-1 mutant had significantly fewer and larger ER bodies than the wild-type. An amino acid substitution of Cys29 with tyrosine (C29Y) on PYK10, a major component protein of ER bodies, was found in leb-1. Non-reducing SDS–PAGE revealed that the electrophoretic mobility of PYK10 in the leb-1 mutant was clearly different from that in the wild type. This difference suggests that the C29Y amino acid substitution caused a tertiary structural change of the PYK10 protein. While the bglu21-1 andpyk10-1 single mutations slightly affected the number and morphology of the ER bodies, a bglu21-1 pyk10-1 double mutant had fewer and larger ER bodies than the wild type. The quantitative ER body phenotypes of leb-1 were similar to those of bglu21-1 pyk10-1 and bglu21-1 leb-1, suggesting that the leb-1 mutation allele acts dominantly to the BGLU21wild-type allele. The leb-1 type PYK10 protein, which has an abnormal structure, may competitively inhibit interactions between the wild-type BGLU21/PYK10 protein and an unknown partner.

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PYK10 Myrosinase Reveals a Functional Coordination between ER Bodies and Glucosinolates in Arabidopsis thaliana

PYK10 Myrosinase Reveals a Functional Coordination between ER Bodies and Glucosinolates in Arabidopsis thaliana | My publications | Scoop.it
The ER body is an organelle derived from the endoplasmic reticulum (ER) that occurs only in three families of the order Brassicales and is suggested to be involved in plant defense. ER bodies in Arabidopsis thaliana contain large amounts of β-glucosidases, but the physiological functions of ER bodies and these enzymes remain largely unclear. Here we show that PYK10, the most abundant β-glucosidase in A. thaliana root ER bodies, hydrolyzes indole glucosinolates (IGs) in addition to the previously reported in vitro substrate scopolin. We found a striking co-expression between ER body-related genes (including PYK10), glucosinolate biosynthetic genes and the genes for so-called specifier proteins affecting the terminal products of myrosinase-mediated glucosinolate metabolism, indicating that these systems have been integrated into a common transcriptional network. Consistent with this, comparative metabolite profiling utilizing a number of A. thaliana relatives within Brassicaceae identified a clear phylogenetic co-occurrence between ER bodies and IGs, but not between ER bodies and scopolin. Collectively, our findings suggest a functional link between ER bodies and glucosinolate metabolisms in planta. In addition, in silico 3D modeling, combined with phylogenomic analysis, suggests that PYK10 represents a clade of 16 myrosinases that arose independently from the other well-documented class of 6 thioglucoside glucohydrolases (TGGs). These findings provide deeper insights into how glucosinolates are metabolized in cruciferous plants and reveal variation of the myrosinase-glucosinolate system within individual plants.
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ER bodies in plants of the Brassicales order: biogenesis and association with innate immunity.

ER bodies in plants of the Brassicales order: biogenesis and association with innate immunity. | My publications | Scoop.it
The endoplasmic reticulum (ER) forms highly organised network structures composed of tubules and cisternae. Many plant species develop additional ER-derived structures, most of which are specific for certain groups of species. In particular, a rod-shaped structure designated as the ER body is produced by plants of the Brassicales order, which includes Arabidopsis thaliana. Genetic analyses and characterisation of A. thaliana mutants possessing a disorganised ER morphology or lacking ER bodies have provided insights into the highly organised mechanisms responsible for the formation of these unique ER structures. The accumulation of proteins specific for the ER body within the ER plays an important role in the formation of ER bodies. However, a mutant that exhibits morphological defects of both the ER and ER bodies has not been identified. This suggests that plants in the Brassicales order have evolved novel mechanisms for the development of this unique organelle, which are distinct from those used to maintain generic ER structures. In A. thaliana, ER bodies are ubiquitous in seedlings and roots, but rare in rosette leaves. Wounding of rosette leaves induces de novo formation of ER bodies, suggesting that these structures are associated with resistance against pathogens and/or herbivores. ER bodies accumulate a large amount of β-glucosidases, which can produce substances that potentially protect against invading pests. Biochemical studies have determined that the enzymatic activities of these β-glucosidases are enhanced during cell collapse. These results suggest that ER bodies are involved in plant immunity, although there is no direct evidence of this. In this review, we provide recent perspectives of ER and ER body formation in A. thaliana, and discuss clues for the functions of ER bodies. We highlight defence strategies against biotic stress that are unique for the Brassicales order, and discuss how ER structures could contribute to these strategies.
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The Plant Cel: GNOM-LIKE1/ERMO1 and SEC24a/ERMO2 Are Required for Maintenance of Endoplasmic Reticulum Morphology in Arabidopsis thaliana

The Plant Cel: GNOM-LIKE1/ERMO1 and SEC24a/ERMO2 Are Required for Maintenance of Endoplasmic Reticulum Morphology in Arabidopsis thaliana | My publications | Scoop.it

The endoplasmic reticulum (ER) is composed of tubules, sheets, and three-way junctions, resulting in a highly conserved polygonal network in all eukaryotes. The molecular mechanisms responsible for the organization of these structures are obscure. To identify novel factors responsible for ER morphology, we employed a forward genetic approach using a transgenic Arabidopsis thalianaplant (GFP-h) with fluorescently labeled ER. We isolated two mutants with defects in ER morphology and designated them endoplasmic reticulum morphology1(ermo1) and ermo2. The cells of both mutants developed a number of ER-derived spherical bodies, ∼1 μm in diameter, in addition to the typical polygonal network of ER. The spherical bodies were distributed throughout the ermo1 cells, while they formed a large aggregate in ermo2 cells. We identified the responsible gene for ermo1 to be GNOM-LIKE1 (GNL1) and the gene for ermo2 to be SEC24a. Homologs of both GNL1 and SEC24a are involved in membrane trafficking between the ER and Golgi in yeast and animal cells. Our findings, however, suggest that GNL1/ERMO1 and SEC24a/ERMO2 have a novel function in ER morphology in higher plants.

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Amazon.co.jp: ゲノムが拓く生態学―遺伝子の網羅的解析で迫る植物の生きざま

Amazon.co.jp: ゲノムが拓く生態学―遺伝子の網羅的解析で迫る植物の生きざま (種生物学研究 第 34号): 永野 惇, 森長 真一, 種生物学会: 本
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