| 1. |
- Boussardon, Clément, et al.
(författare)
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The RPN12a proteasome subunit is essential for the multiple hormonal homeostasis controlling the progression of leaf senescence
- 2022
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Ingår i: Communications Biology. - : Nature Publishing Group. - 2399-3642. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- The 26S proteasome is a conserved multi-subunit machinery in eukaryotes. It selectively degrades ubiquitinated proteins, which in turn provides an efficient molecular mechanism to regulate numerous cellular functions and developmental processes. Here, we studied a new loss-of-function allele of RPN12a, a plant ortholog of the yeast and human structural component of the 19S proteasome RPN12. Combining a set of biochemical and molecular approaches, we confirmed that a rpn12a knock-out had exacerbated 20S and impaired 26S activities. The altered proteasomal activity led to a pleiotropic phenotype affecting both the vegetative growth and reproductive phase of the plant, including a striking repression of leaf senescence associate cell-death. Further investigation demonstrated that RPN12a is involved in the regulation of several conjugates associated with the auxin, cytokinin, ethylene and jasmonic acid homeostasis. Such enhanced aptitude of plant cells for survival in rpn12a contrasts with reports on animals, where 26S proteasome mutants generally show an accelerated cell death phenotype.
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| 2. |
- Law, Simon R., et al.
(författare)
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Darkened leaves use different metabolic strategies for senescence and survival
- 2018
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 177:1, s. 132-150
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Tidskriftsartikel (refereegranskat)abstract
- In plants, an individually darkened leaf initiates senescence much more rapidly than a leaf from a whole darkened plant. Combining transcriptomic and metabolomic approaches in Arabidopsis (Arabidopsis thaliana), we present an overview of the metabolic strategies that are employed in response to different darkening treatments. Under darkened plant conditions, the perception of carbon starvation drove a profound metabolic readjustment in which branched-chain amino acids and potentially monosaccharides released from cell wall loosening became important substrates for maintaining minimal ATP production. Concomitantly, the increased accumulation of amino acids with a high nitrogen-carbon ratio may provide a safety mechanism for the storage of metabolically derived cytotoxic ammonium and a pool of nitrogen for use upon returning to typical growth conditions. Conversely, in individually darkened leaf, the metabolic profiling that followed our 13C-enrichment assays revealed a temporal and differential exchange of metabolites, including sugars and amino acids, between the darkened leaf and the rest of the plant. This active transport could be the basis for a progressive metabolic shift in the substrates fueling mitochondrial activities, which are central to the catabolic reactions facilitating the retrieval of nutrients from the senescing leaf. We propose a model illustrating the specific metabolic strategies employed by leaves in response to these two darkening treatments, which support either rapid senescence or a strong capacity for survival.
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| 3. |
- Liebsch, Daniela, et al.
(författare)
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Metabolic adjustments required for extended leaf longevity under prolonged darkness revealed by a new loss of function allele of PIF5
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Senescence is regulated by a complex interplay of factors and regulatory circuits, which may be accelerated or delayed depending on the integrated signals. Using a forward genetic screen in Arabidopsis thaliana, we identified a mutant strongly delayed in its induction of senescence in response to prolonged darkness. This mutant, which corresponds to a novel loss-of-function allele of PIF5 (PHYTOCHROME-INTERACTING FACTOR 5), exhibits even slightly more extended survival of leaves in darkness than the previously reported pif5-3 TDNA knock-out line. In the present study, we additionally aimed at deciphering the metabolic and regulatory processes conferring this enhanced capacity for survival in pif5 mutants. We combined physiological, metabolomic and transcriptomic analyses, and discovered that the extended survival of mutant leaves in darkness was associated with reduced protein degradation, slight differences in amino acid catabolism related gene expression as well as strong reduction of amino acid transporter expression, which coincided with enhanced amino acid accumulation. Our findings suggest that enhanced survival in darkness could be mediated by moderate levels of protein degradation allowing build up and slow usage of amino acids as alternative respiratory substrates, while during irreversible senescence, strong degradative processes, together with enhanced amino acid transport either to the site of their metabolization inside the leaf, or to other organs in the plant, could promote the fast progression of senescence and antagonize survival. Comparative metabolomics and gene expression analyses suggested that the senescence regulatory network downstream of PIF5 organizes these irreversible stages of leaf senescence, promoting autophagy and amino acid export, possibly by direct binding of important senescence promoting factors like ORE1 to the promoters of some of the involved genes. The failure to induce these later stages may prolong the reversible phase of darkening, thus potentially leading to drastically increased viability of individually darkened leaves under darkness for over 2 weeks.
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| 4. |
- Liebsch, Daniela, et al.
(författare)
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Metabolic control of arginine and ornithine levels paces the progression of leaf senescence
- 2022
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Ingår i: Plant Physiology. - : Oxford University Press. - 0032-0889 .- 1532-2548. ; 189:4, s. 1943-1960
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Tidskriftsartikel (refereegranskat)abstract
- Leaf senescence can be induced by stress or aging, sometimes in a synergistic manner. It is generally acknowledged that the ability to withstand senescence-inducing conditions can provide plants with stress resilience. Although the signaling and transcriptional networks responsible for a delayed senescence phenotype, often referred to as a functional stay-green trait, have been actively investigated, very little is known about the subsequent metabolic adjustments conferring this aptitude to survival. First, using the individually darkened leaf (IDL) experimental setup, we compared IDLs of wild-type (WT) Arabidopsis (Arabidopsis thaliana) to several stay-green contexts, that is IDLs of two functional stay-green mutant lines, oresara1-2 (ore1-2) and an allele of phytochrome-interacting factor 5 (pif5), as well as to leaves from a WT plant entirely darkened (DP). We provide compelling evidence that arginine and ornithine, which accumulate in all stay-green contexts—likely due to the lack of induction of amino acids (AAs) transport—can delay the progression of senescence by fueling the Krebs cycle or the production of polyamines (PAs). Secondly, we show that the conversion of putrescine to spermidine (SPD) is controlled in an age-dependent manner. Thirdly, we demonstrate that SPD represses senescence via interference with ethylene signaling by stabilizing the ETHYLENE BINDING FACTOR1 and 2 (EBF1/2) complex. Taken together, our results identify arginine and ornithine as central metabolites influencing the stress- and age-dependent progression of leaf senescence. We propose that the regulatory loop between the pace of the AA export and the progression of leaf senescence provides the plant with a mechanism to fine-tune the induction of cell death in leaves, which, if triggered unnecessarily, can impede nutrient remobilization and thus plant growth and survival.
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| 5. |
- Routier, Cyril, et al.
(författare)
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Chitosan-modified polyethyleneimine nanoparticles for enhancing the carboxylation reaction and plants' CO2 uptake
- 2023
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 17:4, s. 3430-3441
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Tidskriftsartikel (refereegranskat)abstract
- Increasing plants' photosynthetic efficiency is a major challenge that must be addressed in order to cover the food demands of the growing population in the changing climate. Photosynthesis is greatly limited at the initial carboxylation reaction, where CO2 is converted to the organic acid 3-PGA, catalyzed by the RuBisCO enzyme. RuBisCO has poor affinity for CO2, but also the CO2 concentration at the RuBisCO site is limited by the diffusion of atmospheric CO2 through the various leaf compartments to the reaction site. Beyond genetic engineering, nanotechnology can offer a materials-based approach for enhancing photosynthesis, and yet, it has mostly been explored for the light-dependent reactions. In this work, we developed polyethyleneimine-based nanoparticles for enhancing the carboxylation reaction. We demonstrate that the nanoparticles can capture CO2 in the form of bicarbonate and increase the CO2 that reacts with the RuBisCO enzyme, enhancing the 3-PGA production in in vitro assays by 20%. The nanoparticles can be introduced to the plant via leaf infiltration and, because of the functionalization with chitosan oligomers, they do not induce any toxic effect to the plant. In the leaves, the nanoparticles localize in the apoplastic space but also spontaneously reach the chloroplasts where photosynthetic activity takes place. Their CO2 loading-dependent fluorescence verifies that, in vivo, they maintain their ability to capture CO2 and can be therefore reloaded with atmospheric CO2 while in planta. Our results contribute to the development of a nanomaterials-based CO2-concentrating mechanism in plants that can potentially increase photosynthetic efficiency and overall plants' CO2 storage.
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