| 1. |
- Aubry, Emilie, et al.
(författare)
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A vacuolar hexose transport is required for xylem development in the inflorescence stem
- 2022
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Ingår i: Plant Physiology. - : Oxford University Press. - 0032-0889 .- 1532-2548. ; 188:2, s. 1229-1247
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Tidskriftsartikel (refereegranskat)abstract
- In Angiosperms, the development of the vascular system is controlled by a complex network of transcription factors. However, how nutrient availability in the vascular cells affects their development remains to be addressed. At the cellular level, cytosolic sugar availability is regulated mainly by sugar exchanges at the tonoplast through active and/or facilitated transport. In Arabidopsis (Arabidopsis thaliana), among the genes encoding tonoplastic transporters, SUGAR WILL EVENTUALLY BE EXPORTED TRANSPORTER 16 (SWEET16) and SWEET17 expression has been previously detected in the vascular system. Here, using a reverse genetics approach, we propose that sugar exchanges at the tonoplast, regulated by SWEET16, are important for xylem cell division as revealed in particular by the decreased number of xylem cells in the swt16 mutant and the accumulation of SWEET16 at the procambium-xylem boundary. In addition, we demonstrate that transport of hexoses mediated by SWEET16 and/or SWEET17 is required to sustain the formation of the xylem secondary cell wall. This result is in line with a defect in the xylem cell wall composition as measured by Fourier-transformed infrared spectroscopy in the swt16swt17 double mutant and by upregulation of several genes involved in secondary cell wall synthesis. Our work therefore supports a model in which xylem development partially depends on the exchange of hexoses at the tonoplast of xylem-forming cells.
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| 2. |
- Aubry, Emilie, et al.
(författare)
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Lateral Transport of Organic and Inorganic Solutes
- 2019
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Ingår i: PLANTS. - : MDPI. - 2223-7747. ; 8:1
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Forskningsöversikt (refereegranskat)abstract
- Organic (e.g., sugars and amino acids) and inorganic (e.g., K+, Na+, PO42−, and SO42−) solutes are transported long-distance throughout plants. Lateral movement of these compounds between the xylem and the phloem, and vice versa, has also been reported in several plant species since the 1930s, and is believed to be important in the overall resource allocation. Studies of Arabidopsis thaliana have provided us with a better knowledge of the anatomical framework in which the lateral transport takes place, and have highlighted the role of specialized vascular and perivascular cells as an interface for solute exchanges. Important breakthroughs have also been made, mainly in Arabidopsis, in identifying some of the proteins involved in the cell-to-cell translocation of solutes, most notably a range of plasma membrane transporters that act in different cell types. Finally, in the future, state-of-art imaging techniques should help to better characterize the lateral transport of these compounds on a cellular level. This review brings the lateral transport of sugars and inorganic solutes back into focus and highlights its importance in terms of our overall understanding of plant resource allocation.
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| 3. |
- Castelain, Mathieu, et al.
(författare)
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The non-DNA-binding bHLH transcription factor PRE3/bHLH135/ATBS1/TMO7 is involved in the regulation of light signaling pathway in Arabidopsis
- 2012
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 145, s. 450-460
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Tidskriftsartikel (refereegranskat)abstract
- Plant basic Helix-loop-helix (bHLH) proteins are transcription factors that are involved in many developmental mechanisms, including light signaling and hormone homeostasis. Some of them are non-DNA-binding proteins and could act as dominant negative regulators of other bHLH proteins by forming heterodimers, in a similar way to animal inhibitor of DNA-binding proteins. It has been recently reported that several non-DNA-binding bHLHs are involved in light signaling (KDR/PRE6), gibberellic acid signaling (PRE1/BNQ1/bHLH136) or brassinosteroid signaling (ATBS1). Here we report that Arabidopsis lines overexpressing the PRE3/bHLH135/ATBS1/TMO7 gene are less responsive to red, far-red and blue light than wild-type which is likely to explain the light hyposensitive phenotype displayed when grown under white light conditions. Using quantitative polymerase chain reaction, we show that the expression of PRE3 and KDR/PRE6 genes is regulated by light and that light-related genes are deregulated in the PRE3-ox lines. We show that PRE3 is expressed in the shoot and root meristems and that PRE3-ox lines also have a defect in lateral root development. Our results not only suggest that PRE3 is involved in the regulation of light signaling, but also support the hypothesis that non-DNA-binding bHLH genes are promiscuous genes regulating a wide range of both overlapping and specific regulatory pathways.
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| 4. |
- Chardon, Fabien, et al.
(författare)
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Natural variation in the long-distance transport of nutrients and photoassimilates in response to N availability
- 2022
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Ingår i: Journal of plant physiology (Print). - : Elsevier. - 0176-1617 .- 1618-1328. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- Phloem and xylem tissues are necessary for the allocation of nutrients and photoassimilates. However, how the long-distance transport of carbon (C) and nitrogen (N) is coordinated with the central metabolism is largely unknown. To better understand how the genetic and environmental factors influence C and N transport, we analysed the metabolite profiles of phloem exudates and xylem saps of five Arabidopsis thaliana accessions grown in low or non-limiting N supply. We observed that xylem saps were composed of 46 or 56% carbohydrates, 27 or 45% amino acids, and 5 or 13% organic acids in low or non-limiting N supply, respectively. In contrast, phloem exudates were composed of 76 or 86% carbohydrates, 7 or 18% amino acids, and 5 or 6% organic acids. Variation in N supply impacted amino acid, organic acid and sugar contents. When comparing low N and non-limiting N, the most striking differences were variations of glutamine, aspartate, and succinate abundance in the xylem saps and citrate and fumarate abundance in phloem exudates. In addition, we observed a substantial variation of metabolite content between genotypes, particularly under high N. The content of several organic acids, such as malate, citrate, fumarate, and succinate was affected by the genotype alone or by the interaction between genotype and N supply. This study confirmed that the response of the transport of nutrients in the phloem and the xylem to N availability is associated with the regulation of the central metabolism and could be an adaptive trait.
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| 5. |
- Klemens, Patrick A. W., et al.
(författare)
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Overexpression of the Vacuolar Sugar Carrier AtSWEET16 Modifies Germination, Growth, and Stress Tolerance in Arabidopsis
- 2013
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Ingår i: Plant Physiology. - : American Society of Plant Biologists. - 0032-0889 .- 1532-2548. ; 163:3, s. 1338-1352
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Tidskriftsartikel (refereegranskat)abstract
- Here, we report that SUGARS WILL EVENTUALLY BE EXPORTED TRANSPORTER (SWEET16) from Arabidopsis (Arabidopsis thaliana) is a vacuole-located carrier, transporting glucose (Glc), fructose (Fru), and sucrose (Suc) after heterologous expression in Xenopus laevis oocytes. The SWEET16 gene, similar to the homologs gene SWEET17, is mainly expressed in vascular parenchyma cells. Application of Glc, Fru, or Suc, as well as cold, osmotic stress, or low nitrogen, provoke the down-regulation of SWEET16 messenger RNA accumulation. SWEET16 overexpressors (35S(Pro):SWEET16) showed a number of peculiarities related to differences in sugar accumulation, such as less Glc, Fru, and Suc at the end of the night. Under cold stress, 35S(Pro):SWEET16 plants are unable to accumulate Fru, while under nitrogen starvation, both Glc and Fru, but not Suc, were less abundant. These changes of individual sugars indicate that the consequences of an increased SWEET16 activity are dependent upon the type of external stimulus. Remarkably, 35S(Pro):SWEET16 lines showed improved germination and increased freezing tolerance. The latter observation, in combination with the modified sugar levels, points to a superior function of Glc and Suc for frost tolerance. 35S(Pro):SWEET16 plants exhibited increased growth efficiency when cultivated on soil and showed improved nitrogen use efficiency when nitrate was sufficiently available, while under conditions of limiting nitrogen, wild-type biomasses were higher than those of 35S(Pro):SWEET16 plants. Our results identify SWEET16 as a vacuolar sugar facilitator, demonstrate the substantial impact of SWEET16 overexpression on various critical plant traits, and imply that SWEET16 activity must be tightly regulated to allow optimal Arabidopsis development under nonfavorable conditions.
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| 6. |
- Lakehal, Abdellah, et al.
(författare)
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A Molecular Framework for the Control of Adventitious Rooting by TIR1/AFB2-Aux/IAA-Dependent Auxin Signaling in Arabidopsis
- 2019
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Ingår i: Molecular Plant. - : Elsevier. - 1674-2052 .- 1752-9867. ; 12:11, s. 1499-1514
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Tidskriftsartikel (refereegranskat)abstract
- In Arabidopsis thaliana, canonical auxin-dependent gene regulation is mediated by 23 transcription factors from the AUXIN RESPONSE FACTOR (ARF) family that interact with auxin/indole acetic acid repressors (Aux/IAAs), which themselves form co-receptor complexes with one of six TRANSPORT INHIBITOR1/AUXIN-SIGNALLING F-BOX (TIR1/AFB) proteins. Different combinations of co-receptors drive specific sensing outputs, allowing auxin to control a myriad of processes. ARF6 and ARF8 are positive regulators of adventitious root initiation upstream of jasmonate, but the exact auxin co-receptor complexes controlling the transcriptional activity of these proteins has remained unknown. Here, using loss-of-function mutants we show that three Aux/IAA genes, IAA6, IAA9, and IAA17, act additively in the control of adventitious root (AR) initiation. These three IAA proteins interact with ARF6 and/or ARF8 and likely repress their activity in AR development. We show that TIR1 and AFB2 are positive regulators of AR formation and TIR1 plays a dual role in the control of jasmonic acid (JA) biosynthesis and conjugation, as several JA biosynthesis genes are up-regulated in the tir1-1 mutant. These results lead us to propose that in the presence of auxin, TIR1 and AFB2 form specific sensing complexes with IAA6, IAA9, and/or IAA17 to modulate JA homeostasis and control AR initiation.
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| 7. |
- Le Hir, Rozenn, et al.
(författare)
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ABCG9, ABCG11 and ABCG14 ABC transporters are required for vascular development in Arabidopsis
- 2013
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Ingår i: The Plant Journal. - : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 76:5, s. 811-824
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain insights into the regulatory pathways controlling phloem development, we characterized three genes encoding membrane proteins from the G sub-family of ABC transporters (ABCG9, ABCG11 and ABCG14), whose expression in the phloem has been confirmed. Mutations in the genes encoding these dimerizing half transporters' are semi-dominant and result in vascular patterning defects in cotyledons and the floral stem. Co-immunoprecipitation and bimolecular fluorescence complementation experiments demonstrated that these proteins dimerize, either by flexible pairing (ABCG11 and ABCG9) or by forming strict heterodimers (ABCG14). In addition, metabolome analyses and measurement of sterol ester contents in the mutants suggested that ABCG9, ABCG11 and ABCG14 are involved in lipid/sterol homeostasis regulation. Our results show that these three ABCG genes are required for proper vascular development in Arabidopsis thaliana.
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| 8. |
- Le Hir, Rozenn, et al.
(författare)
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AtbHLH68 transcription factor contributes to the regulation of ABA homeostasis and drought stress tolerance in Arabidopsis thaliana
- 2017
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Ingår i: Physiologia Plantarum. - : Wiley-Blackwell. - 0031-9317 .- 1399-3054. ; 160:3, s. 312-327
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Tidskriftsartikel (refereegranskat)abstract
- Basic helix-loop-helix (bHLH) transcription factors are involved in a wide range of developmental processes and in response to biotic and abiotic stresses. They represent one of the biggest families of transcription factors but only few of them have been functionally characterized. Here we report the characterization of AtbHLH68 and show that, although the knock out mutant did not have an obvious development phenotype, it was slightly more sensitive to drought stress than the Col-0, and AtbHLH68 overexpressing lines displayed defects in lateral root (LR) formation and a significant increased tolerance to drought stress, likely related to an enhanced sensitivity to abscisic acid (ABA) and/or increased ABA content. AtbHLH68 was expressed in the vascular system of Arabidopsis and its expression was modulated by exogenously applied ABA in an organ-specific manner. We showed that the expression of genes involved in ABA metabolism [AtAAO3 (AtALDEHYDE OXIDASE 3) and AtCYP707A3 (AtABSCISIC ACID 8HYDROXYLASE 3)], in ABA-related response to drought-stress (AtMYC2, AtbHLH122 and AtRD29A) or during LRs development (AtMYC2 and AtABI3) was de-regulated in the overexpressing lines. We propose that AtbHLH68 has a function in the regulation of LR elongation, and in the response to drought stress, likely through an ABA-dependent pathway by regulating directly or indirectly components of ABA signaling and/or metabolism.
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| 9. |
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| 10. |
- Le Hir, Rozenn, et al.
(författare)
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Gene expression profiling : keys for investigating phloem functions
- 2008
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Ingår i: Trends in Plant Science. - : Elsevier BV. - 1360-1385 .- 1878-4372. ; 13:6, s. 273-280
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Forskningsöversikt (refereegranskat)abstract
- Phloem is the major route for transport of carbohydrates, amino acids, and other nutrients from source to sink tissues. Hormones, mRNAs, small RNAs and proteins also are transported by the phloem, and potentially play pivotal roles in communication between organs to coordinate plant development and physiology. A comprehensive understanding of the mechanisms involved in phloem transport and signalling is still lacking. Recent transcript profiling in several plant species has provided new insights to phloem-specialized functions. Here, we review conclusions regarding the unique functions of the phloem and discuss putative roles for mRNAs and small RNA species in long-distance signalling.
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