| 1. |
- Christensen, Anna, et al.
(författare)
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Higher plant calreticulins have acquired specialized functions in arabidopsis
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:6, s. e11342-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Calreticulin (CRT) is a ubiquitous ER protein involved in multiple cellular processes in animals, such as protein folding and calcium homeostasis. Like in animals, plants have evolved divergent CRTs, but their physiological functions are less understood. Arabidopsis contains three CRT proteins, where the two CRTs AtCRT1a and CRT1b represent one subgroup, and AtCRT3 a divergent member. Methodology/Principal Findings: Through expression of single Arabidopsis family members in CRT-deficient mouse fibroblasts we show that both subgroups have retained basic CRT functions, including ER Ca2+-holding potential and putative chaperone capabilities. However, other more general cellular defects due to the absence of CRT in the fibroblasts, such as cell adhesion deficiencies, were not fully restored. Furthermore, in planta expression, protein localization and mutant analyses revealed that the three Arabidopsis CRTs have acquired specialized functions. The AtCRT1a and CRT1b family members appear to be components of a general ER chaperone network. In contrast, and as recently shown, AtCRT3 is associated with immune responses, and is essential for responsiveness to the bacterial Pathogen-Associated Molecular Pattern (PAMP) elf18, derived from elongation factor (EF)-Tu. Whereas constitutively expressed AtCRT1a fully complemented Atcrt1b mutants, AtCRT3 did not. Conclusions/Significance: We conclude that the physiological functions of the two CRT subgroups in Arabidopsis have diverged, resulting in a role for AtCRT3 in PAMP associated responses, and possibly more general chaperone functions for AtCRT1a and CRT1b.
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| 2. |
- Thiergart, Thorsten, et al.
(författare)
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Root microbiota assembly and adaptive differentiation among European Arabidopsis populations
- 2020
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Ingår i: Nature Ecology & Evolution. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 4:1, s. 122-131
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Tidskriftsartikel (refereegranskat)abstract
- Across large spatial scales, climate is more important than soil conditions for plant adaptation and variation in root-associated filamentous eukaryotic communities. Factors that drive continental-scale variation in root microbiota and plant adaptation are poorly understood. We monitored root-associated microbial communities in Arabidopsis thaliana and co-occurring grasses at 17 European sites across 3 years. We observed strong geographic structuring of the soil biome, but not of the root microbiota. A few phylogenetically diverse and geographically widespread bacteria consistently colonized plant roots. Among-site and across-year similarity in microbial community composition was stronger for the bacterial root microbiota than for filamentous eukaryotes. In a reciprocal transplant between two A. thaliana populations in Sweden and Italy, we uncoupled soil from location effects and tested their contributions to root microbiota variation and plant adaptation. Community differentiation in plant roots was explained primarily by location for filamentous eukaryotes and by soil origin for bacteria, whereas host genotype effects were marginal. Strong local adaptation between the two A. thaliana populations was observed, with differences in soil properties and microbes of little importance for the observed magnitude of adaptive differentiation. Our results suggest that, across large spatial scales, climate is more important than soil conditions for plant adaptation and variation in root-associated filamentous eukaryotic communities, whereas soil properties are primary drivers of bacterial community differentiation in roots.
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| 3. |
- Zamioudis, Christos, et al.
(författare)
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Rhizobacterial volatiles and photosynthesis-related signals coordinate MYB72 expression in Arabidopsis roots during onset of induced systemic resistance and iron-deficiency responses
- 2015
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 84:2, s. 309-322
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Tidskriftsartikel (refereegranskat)abstract
- In Arabidopsis roots, the transcription factor MYB72 plays a dual role in the onset of rhizobacteria-induced systemic resistance (ISR) and plant survival under conditions of limited iron availability. Previously, it was shown that MYB72 coordinates the expression of a gene module that promotes synthesis and excretion of iron-mobilizing phenolic compounds in the rhizosphere, a process that is involved in both iron acquisition and ISR signaling. Here, we show that volatile organic compounds (VOCs) from ISR-inducing Pseudomonas bacteria are important elicitors of MYB72. In response to VOC treatment, MYB72 is co-expressed with the iron uptake-related genes FERRIC REDUCTION OXIDASE2 (FRO2) and IRON-REGULATED TRANSPORTER1 (IRT1) in a manner that is dependent on FER-LIKE IRON DEFICIENCY TRANSCRIPTION FACTOR (FIT), indicating that MYB72 is an intrinsic part of the plant's iron-acquisition response that is typically activated upon iron starvation. However, VOC-induced MYB72 expression is activated independently of iron availability in the root vicinity. Moreover, rhizobacterial VOC-mediated induction of MYB72 requires photosynthesis-related signals, while iron deficiency in the rhizosphere activates MYB72 in the absence of shoot-derived signals. Together, these results show that the ISR- and iron acquisition-related transcription factor MYB72 in Arabidopsis roots is activated by rhizobacterial volatiles and photosynthesis-related signals, and enhances the iron-acquisition capacity of roots independently of the iron availability in the rhizosphere. This work highlights the role of MYB72 in plant processes by which root microbiota simultaneously stimulate systemic immunity and activate the iron-uptake machinery in their host plants. Significance Statement Plant roots intimately interact with plant growth-promoting rhizobacteria that prime the plant immune system and aid in iron uptake two functions facilitated by the root-specific transcription factor MYB72. Here we show how MYB72 and iron uptake responses are systemically activated by photosynthesis-related signals and volatiles produced by plant growth-promoting rhizobacteria, highlighting the important role of beneficial root microbiota in supporting plant growth and health.
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