| 1. |
- Pencik, Ales, et al.
(author)
-
Regulation of Auxin Homeostasis and Gradients in Arabidopsis Roots through the Formation of the Indole-3-Acetic Acid Catabolite 2-Oxindole-3-Acetic Acid
- 2013
-
In: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 25:10, s. 3858-3870
-
Journal article (peer-reviewed)abstract
- The native auxin, indole-3-acetic acid (IAA), is a major regulator of plant growth and development. Its nonuniform distribution between cells and tissues underlies the spatiotemporal coordination of many developmental events and responses to environmental stimuli. The regulation of auxin gradients and the formation of auxin maxima/minima most likely involve the regulation of both metabolic and transport processes. In this article, we have demonstrated that 2-oxindole-3-acetic acid (oxIAA) is a major primary IAA catabolite formed in Arabidopsis thaliana root tissues. OxIAA had little biological activity and was formed rapidly and irreversibly in response to increases in auxin levels. We further showed that there is cell type-specific regulation of oxIAA levels in the Arabidopsis root apex. We propose that oxIAA is an important element in the regulation of output from auxin gradients and, therefore, in the regulation of auxin homeostasis and response mechanisms.
|
|
| 2. |
- Boussardon, Clément, et al.
(author)
-
The RPN12a proteasome subunit is essential for the multiple hormonal homeostasis controlling the progression of leaf senescence
- 2022
-
In: Communications Biology. - : Nature Publishing Group. - 2399-3642. ; 5:1
-
Journal article (peer-reviewed)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.
|
|
| 3. |
- Antoniadi, Ioanna, et al.
(author)
-
Fluorescence-activated multi-organelle mapping of subcellular plant hormone distribution
- 2023
-
In: Plant Journal. - 0960-7412 .- 1365-313X. ; 116, s. 1825-1841
-
Journal article (peer-reviewed)abstract
- Auxins and cytokinins are two major families of phytohormones that control most aspects of plant growth, development and plasticity. Their distribution in plants has been described, but the importance of cell- and subcellular-type specific phytohormone homeostasis remains undefined. Herein, we revealed auxin and cytokinin distribution maps showing their different organelle-specific allocations within the Arabidopsis plant cell. To do so, we have developed Fluorescence-Activated multi-Organelle Sorting (FAmOS), an innovative subcellular fractionation technique based on flow cytometric principles. FAmOS allows the simultaneous sorting of four differently labelled organelles based on their individual light scatter and fluorescence parameters while ensuring hormone metabolic stability. Our data showed different subcellular distribution of auxin and cytokinins, revealing the formation of phytohormone gradients that have been suggested by the subcellular localization of auxin and cytokinin transporters, receptors and metabolic enzymes. Both hormones showed enrichment in vacuoles, while cytokinins were also accumulated in the endoplasmic reticulum.
|
|
| 4. |
- Bhalerao, Rishikesh P, et al.
(author)
-
Shoot-derived auxin is essential for early lateral root emergence in Arabidopsis seedlings
- 2002
-
In: The Plant Journal. - : Blackwell Publishing. - 0960-7412 .- 1365-313X. ; 29:3, s. 325-332
-
Journal article (peer-reviewed)abstract
- Lateral root formation is profoundly affected by auxins. Here we present data which indicate that light influences the formation of indole-3-acetic acid (IAA) in germinating Arabidopsis seedlings. IAA transported from the developing leaves to the root system is detectable as a short-lived pulse in the roots and is required for the emergence of the lateral root primordia (LRP) during early seedling development. LRP emergence is inhibited by the removal of apical tissues prior to detection of the IAA pulse in the root, but this treatment has minimal effects on LRP initiation. Our results identify the first developing true leaves as the most likely source for the IAA required for the first emergence of the LRP, as removal of cotyledons has only a minor effect on LRP emergence in contrast to removal of the leaves. A basipetal IAA concentration gradient with high levels of IAA in the root tip appears to control LRP initiation, in contrast to their emergence. A significant increase in the ability of the root system to synthesize IAA is observed 10 days after germination, and this in turn is reflected in the reduced dependence of the lateral root emergence on aerial tissue-derived auxin at this stage. We propose a model for lateral root formation during early seedling development that can be divided into two phases: (i) an LRP initiation phase dependent on a root tip-localized IAA source, and (ii) an LRP emergence phase dependent on leaf-derived IAA up to 10 days after germination.
|
|
| 5. |
- Ljung, Karin
(author)
-
Fruit Growth in Arabidopsis Occurs via DELLA-Dependent and DELLA-Independent Gibberellin Responses
- 2012
-
In: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 24, s. 3982-3996
-
Journal article (peer-reviewed)abstract
- Fruit growth and development depend on highly coordinated hormonal activities. The phytohormone gibberellin (GA) promotes growth by inducing degradation of the growth-repressing DELLA proteins; however, the extent to which DELLA proteins contribute to GA-mediated gynoecium and fruit development remains to be clarified. Here, we provide an in-depth characterization of the role of DELLA proteins in Arabidopsis thaliana fruit growth. We show that DELLA proteins are key regulators of reproductive organ size and important for ensuring optimal fertilization. We demonstrate that the seedless fruit growth (parthenocarpy) observed in della mutants can be directly attributed to the constitutive activation of GA signaling. It has been known for > 75 years that another hormone, auxin, can induce formation of seedless fruits. Using mutants with complete lack of DELLA activity, we show here that auxin-induced parthenocarpy occurs entirely through GA signaling in Arabidopsis. Finally, we uncover the existence of a DELLA-independent GA response that promotes fruit growth. This response requires GIBBERELLIN-INSENSITIVE DWARF1-mediated GA perception and a functional 26S proteasome and involves the basic helix-loop-helix protein SPATULA as a key component. Taken together, our results describe additional complexities in GA signaling during fruit development, which may be particularly important to optimize the conditions for successful reproduction.
|
|
| 6. |
- Ljung, Karin, et al.
(author)
-
Surveillance of cell wall diffusion barrier integrity modulates water and solute transport in plants
- 2019
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Journal article (peer-reviewed)abstract
- The endodermis is a key cell layer in plant roots that contributes to the controlled uptake of water and mineral nutrients into plants. In order to provide such functionality the endodermal cell wall has specific chemical modifications consisting of lignin bands (Casparian strips) that encircle each cell, and deposition of a waxy-like substance (suberin) between the wall and the plasma membrane. These two extracellular deposits provide control of diffusion enabling the endodermis to direct the movement of water and solutes into and out of the vascular system in roots. Loss of integrity of the Casparian strip-based apoplastic barrier is sensed by the leakage of a small peptide from the stele into the cortex. Here, we report that such sensing of barrier integrity leads to the rebalancing of water and mineral nutrient uptake, compensating for breakage of Casparian strips. This rebalancing involves both a reduction in root hydraulic conductivity driven by deactivation of aquaporins, and downstream limitation of ion leakage through deposition of suberin. These responses in the root are also coupled to a reduction in water demand in the shoot mediated by ABA-dependent stomatal closure.
|
|
| 7. |
|
|
| 8. |
- Ntefidou, Maria, et al.
(author)
-
Physcomitrium patens PpRIC, an ancestral CRIB-domain ROP effector, inhibits auxin-induced differentiation of apical initial cells
- 2023
-
In: Cell Reports. - : Elsevier. - 2211-1247. ; 42:2
-
Journal article (peer-reviewed)abstract
- RHO guanosine triphosphatases are important eukaryotic regulators of cell differentiation and behavior. Plant ROP (RHO of plant) family members activate specific, incompletely characterized downstream signaling. The structurally simple land plant Physcomitrium patens is missing homologs of key animal and flowering plant RHO effectors but contains a single CRIB (CDC42/RAC interactive binding)-domain -contain-ing RIC (ROP-interacting CRIB-containing) protein (PpRIC). Protonemal P. patens filaments elongate based on regular division and PpROP-dependent tip growth of apical initial cells, which upon stimulation by the hor-mone auxin differentiate caulonemal characteristics. PpRIC interacts with active PpROP1, co-localizes with this protein at the plasma membrane at the tip of apical initial cells, and accumulates in the nucleus. Remark-ably, PpRIC is not required for tip growth but is targeted to the nucleus to block caulonema differentiation downstream of auxin-controlled gene expression. These observations establish functions of PpRIC in medi-ating crosstalk between ROP and auxin signaling, which contributes to the maintenance of apical initial cell identity.
|
|
| 9. |
- Yin, Xiao-Jun, et al.
(author)
-
Ubiquitin lysine 63 chain forming ligases regulate apical dominance in Arabidopsis
- 2007
-
In: The Plant Cell. - Rockville : American society of plant biologists. - 1040-4651 .- 1532-298X. ; 19:6, s. 1898-1911
-
Journal article (peer-reviewed)abstract
- Lys-63-linked multiubiquitin chains play important roles in signal transduction in yeast and in mammals, but the functions for this type of chain in plants remain to be defined. The RING domain protein RGLG2 (for RING domain Ligase2) from Arabidopsis thaliana can be N-terminally myristoylated and localizes to the plasma membrane. It can form Lys-63-linked multiubiquitin chains in an in vitro reaction. RGLG2 has overlapping functions with its closest sequelog, RGLG1, and single mutants in either gene are inconspicuous. rglg1 rglg2 double mutant plants exhibit loss of apical dominance and altered phyllotaxy, two traits critically influenced by the plant hormone auxin. Auxin and cytokinin levels are changed, and the plants show a decreased response to exogenously added auxin. Changes in the abundance of PIN family auxin transport proteins and synthetic lethality with a mutation in the auxin transport regulator BIG suggest that the directional flow of auxin is modulated by RGLG activity. Modification of proteins by Lys-63-linked multiubiquitin chains is thus important for hormone-regulated, basic plant architecture.
|
|
| 10. |
- Antoniadi, Ioanna, et al.
(author)
-
Best practices in plant cytometry
- 2021
-
In: Cytometry Part A. - : Wiley. - 1552-4922 .- 1552-4930. ; 99, s. 311-317
-
Journal article (peer-reviewed)
|
|
