| 1. |
- Darwish, Essam, et al.
(författare)
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Touch signaling and thigmomorphogenesis are regulated by complementary CAMTA3- and JA-dependent pathways
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:20
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Tidskriftsartikel (refereegranskat)abstract
- Plants respond to mechanical stimuli to direct their growth and counteract environmental threats. Mechanical stimulation triggers rapid gene expression changes and affects plant appearance (thigmomorphogenesis) and flowering. Previous studies reported the importance of jasmonic acid (JA) in touch signaling. Here, we used reverse genetics to further characterize the molecular mechanisms underlying touch signaling. We show that Piezo mechanosensitive ion channels have no major role in touch-induced gene expression and thigmomorphogenesis. In contrast, the receptor-like kinase Feronia acts as a strong negative regulator of the JA-dependent branch of touch signaling. Last, we show that calmodulin-binding transcriptional activators CAMTA1/2/3 are key regulators of JA-independent touch signaling. CAMTA1/2/3 cooperate to directly bind the promoters and activate gene expression of JA-independent touch marker genes like TCH2 and TCH4. In agreement, camta3 mutants show a near complete loss of thigmomorphogenesis and touch-induced delay of flowering. In conclusion, we have now identified key regulators of two independent touch-signaling pathways.
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| 2. |
- Kimura, Sachie, et al.
(författare)
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CRK2 and C-terminal phosphorylation of NADPH oxidase RBOHD regulate reactive oxygen species production in arabidopsis
- 2020
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 32:4, s. 1063-1080
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Tidskriftsartikel (refereegranskat)abstract
- Reactive oxygen species (ROS) are important messengers in eukaryotic organisms, and their production is tightly controlled. Active extracellular ROS production by NADPH oxidases in plants is triggered by receptor-like protein kinase-dependent signaling networks. Here, we show that CYSTEINE-RICH RLK2 (CRK2) kinase activity is required for plant growth and CRK2 exists in a preformed complex with the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) in Arabidopsis (Arabidopsis thaliana). Functional CRK2 is required for the full elicitor-induced ROS burst, and consequently the crk2 mutant is impaired in defense against the bacterial pathogen Pseudomonas syringae pv tomato DC3000. Our work demonstrates that CRK2 regulates plant innate immunity. We identified in vitro CRK2-dependent phosphorylation sites in the C-terminal region of RBOHD. Phosphorylation of S703 RBOHD is enhanced upon flg22 treatment, and substitution of S703 with Ala reduced ROS production in Arabidopsis. Phylogenetic analysis suggests that phospho-sites in the C-terminal region of RBOHD are conserved throughout the plant lineage and between animals and plants. We propose that regulation of NADPH oxidase activity by phosphorylation of the C-terminal region might be an ancient mechanism and that CRK2 is an important element in regulating microbe-associated molecular pattern-triggered ROS production.
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| 3. |
- Tran, Huy Cuong, et al.
(författare)
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An mTRAN-mRNA interaction mediates mitochondrial translation initiation in plants
- 2023
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Ingår i: Science. - 1095-9203. ; 381:6661
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Tidskriftsartikel (refereegranskat)abstract
- Plant mitochondria represent the largest group of respiring organelles on the planet. Plant mitochondrial messenger RNAs (mRNAs) lack Shine-Dalgarno-like ribosome-binding sites, so it is unknown how plant mitoribosomes recognize mRNA. We show that “mitochondrial translation factors” mTRAN1 and mTRAN2 are land plant–specific proteins, required for normal mitochondrial respiration chain biogenesis. Our studies suggest that mTRANs are noncanonical pentatricopeptide repeat (PPR)–like RNA binding proteins of the mitoribosomal “small” subunit. We identified conserved Adenosine (A)/Uridine (U)-rich motifs in the 5′ regions of plant mitochondrial mRNAs. mTRAN1 binds this motif, suggesting that it is a mitoribosome homing factor to identify mRNAs. We demonstrate that mTRANs are likely required for translation of all plant mitochondrial mRNAs. Plant mitochondrial translation initiation thus appears to use a protein-mRNA interaction that is divergent from bacteria or mammalian mitochondria.
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| 4. |
- Tran, Huy Cuong
(författare)
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Characterization of land plant-specific proteins required for mitochondrial translation initiation
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant mitochondria produce the majority of adenosine triphosphate (ATP) – the cellular energy currency for metabolic reactions needed for plant growth, development, and maintenance. Despite a relatively thorough understanding of basic mitochondrial functions, many mitochondrial proteins and processes remain poorly understood. The aims of this thesis are to i) review and compare the mitochondrial unfolded protein response (UPRmt) and related signalling across eukaryotic kingdoms, to ii) describe an efficient isolation method of Arabidopsis mitochondria using continuous Percoll density gradients, and to iii) characterize two Arabidopsis thaliana genes, mTRAN1 and mTRAN2. Paper I summarizes the current knowledge of UPRmt across eukaryotic kingdoms, and describes a meta-analysis of UPRmt regulators and target genes. UPRmt is a mitochondria-to-nucleus “retrograde” response that regulates nuclear gene expression during mitochondrial dysfunction to maintain mitochondrial homeostasis. Although UPRmt has been extensively studied in animals, relatively little is known about the plant UPRmt and only few regulators have recently been identified. In yeast, very few unfolded protein responses that seem to be related to UPRmt have been described. Here, the UPRmt in animals, yeast and plants are compared. Our study indicates that each kingdom has evolved their own specific regulators, which however induce very similar groups of target genes. Our meta-analysis identifies homologs of known UPRmt regulators and responsive genes across eukaryotic kingdoms.Paper II describes a strategy for efficient purification of Arabidopsis mitochondria using continuous Percoll density gradients. By using this method, the purity of isolated mitochondria is greatly improved. Obtained mitochondria can be either used for assays requiring highly intact and functional mitochondria, e.g. import assay or respiration measurement, or be stored for later use, e.g. BN-PAGE or western blot.Paper III describes the characterization of two Arabidopsis thaliana genes that we named as named as mitochondrial TRANslation factor 1 (mTRAN1) and 2 (mTRAN2). Here, mTRAN1 and mTRAN2 are shown to be land plant-specific mitochondrial proteins that are critical for plant performance, but they are unlikely to be adenyl cyclases as previously annotated. Interestingly, knocking out both mTRAN1 and mTRAN2 results in low abundance and activity of mitochondrial oxidative phosphorylation complexes. Using co-immunoprecipitation, mTRAN1 and mTRAN2 are confirmed to be part of the mitoribosome small subunit (mtSSU). In organello protein synthesis and polysome fractionation assays suggest that mTRANs are required for mitochondrial translation initiation. Moreover, the RNA electrophoretic mobility shift assays suggest that mTRAN1 binds to the A/U-rich regions in the 5’-untranslated regions of mitochondrial mRNAs to mediate mtSSU-mRNA binding to initiate translation. Finally, our mitoribosome profiling suggests that mTRAN proteins are universal mtSSU-embedded translation initiation factors. Together, these findings suggest that mitochondrial translation initiation occurs via a unique mechanism in plants, as compared to in bacteria, yeast and mammals.
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| 5. |
- Tran, Huy Cuong, et al.
(författare)
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Mitochondrial unfolded protein-related responses across kingdoms : similar problems, different regulators
- 2020
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Ingår i: Mitochondrion. - : Elsevier BV. - 1567-7249. ; 53, s. 166-177
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Forskningsöversikt (refereegranskat)abstract
- Mitochondria are key components of eukaryotic cells, so their proper functioning is monitored via different mitochondrial signalling responses. One of these mitochondria-to-nuclear ‘retrograde’ responses to maintain mitochondrial homeostasis is the mitochondrial unfolded protein response (UPRmt), which can be activated by a variety of defects including blocking mitochondrial translation, respiration, protein import or transmembrane potential. Although UPRmt was first reported in cultured mammalian cells, this signalling pathway has also been extensively studied in the nematode Caenorhabditis elegans. In yeast, there are no published studies focusing on UPRmt in a strict sense, but other unfolded protein responses (UPR) that appear related to UPRmt have been described, such as the UPR activated by protein mistargeting (UPRam) and mitochondrial compromised protein import response (mitoCPR). In plants, very little is known about UPRmt and only recently some of the regulators have been identified. In this paper, we summarise and compare the current knowledge of the UPRmt and related responses across eukaryotic kingdoms: animals, fungi and plants. Our comparison suggests that each kingdom has evolved its own specific set of regulators, however, the functional categories represented among UPRmt–related target genes appear to be largely overlapping. This indicates that the strategies for preserving proper mitochondrial functions are partially conserved, targeting mitochondrial chaperones, proteases, import components, dynamics and stress response, but likely also non-mitochondrial functions including growth regulators/hormone balance and amino acid metabolism. We also identify homologs of known UPRmt regulators and responsive genes across kingdoms, which may be interesting targets for future research.
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| 6. |
- Tran, Huy Cuong, et al.
(författare)
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Purification of Leaf Mitochondria from Arabidopsis thaliana Using Percoll Density Gradients
- 2022
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Ingår i: Plant Mitochondria : Methods and Protocols - Methods and Protocols. - New York, NY : Springer US. - 1940-6029 .- 1064-3745. - 9781071616529 - 9781071616536 ; 2363, s. 1-12
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Bokkapitel (refereegranskat)abstract
- The study of plant mitochondria often requires isolation of mitochondria from plant tissues in intact and functional form. Here, we describe an effective procedure of mitochondrial isolation from leaf tissues and whole seedlings of the model dicot species Arabidopsis thaliana by using differential centrifugation and continuous Percoll density gradients.
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