1
|
Chua A, Sherwood OL, Fitzhenry L, Ng CKY, McCabe PF, Daly CT. Cyanobacteria-Derived Proline Increases Stress Tolerance in Arabidopsis thaliana Root Hairs by Suppressing Programmed Cell Death. FRONTIERS IN PLANT SCIENCE 2020; 11:490075. [PMID: 33381127 PMCID: PMC7768022 DOI: 10.3389/fpls.2020.490075] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 11/25/2020] [Indexed: 05/31/2023]
Abstract
Nitrogen-fixing heterocystous cyanobacteria are used as biofertilizer inoculants for stimulating plant growth but can also alleviate plant stress by exometabolite secretion. However, only a small number of studies have focused on elucidating the identity of said bioactives because of the wide array of exuded compounds. Here, we used the root hair assay (RHA) as a rapid programmed cell death (PCD) screening tool for characterizing the bioactivity of cyanobacteria Nostoc muscorum conditioned medium (CM) on Arabidopsis thaliana root hair stress tolerance. We found that heat-stressed A. thaliana pre-treated with N. muscorum CM fractions exhibited significantly lower root hair PCD levels compared to untreated seedlings. Treatment with CM increased stress tolerance by suppressing PCD in root hairs but not necrosis, indicating the bioactive compound was specifically modulating the PCD pathway and not a general stress response. Based on documented N. muscorum exometabolites, we identified the stress-responsive proline as a compound of interest and strong evidence from the ninhydrin assay and HPLC indicate that proline is present in N. muscorum CM. To establish whether proline was capable of suppressing PCD, we conducted proline supplementation experiments. Our results showed that exogenous proline had a similar effect on root hairs as N. muscorum CM treatment, with comparable PCD suppression levels and insignificant necrosis changes. To verify proline as one of the biologically active compounds in N. muscorum CM, we used three mutant A. thaliana lines with proline transporter mutations (lht1, aap1 and atprot1-1::atprot2-3::atprot3-2). Compared with the wild-type seedlings, PCD-suppression in lht1and aap1 mutants was significantly reduced when supplied with low proline (1-5 μM) levels. Similarly, pre-treatment with N. muscorum CM resulted in elevated PCD levels in all three mutant lines compared to wild-type seedlings. Our results show that plant uptake of cyanobacteria-derived proline alters their root hair PCD sensitivity threshold. This offers evidence of a novel biofertilizer mechanism for reducing stress-induced PCD levels, independent of the existing mechanisms documented in the literature.
Collapse
Affiliation(s)
- Alysha Chua
- Department of Science, Waterford Institute of Technology, Waterford, Ireland
- Pharmaceutical and Molecular Biotechnology Research Centre (PMBRC), Waterford Institute of Technology, Waterford, Ireland
- Eco-Innovation Research Centre (EIRC), Waterford Institute of Technology, Waterford, Ireland
| | - Orla L. Sherwood
- UCD School of Biology and Environmental Science, University College Dublin, Dublin, Ireland
- UCD Centre for Plant Science, University College Dublin, Dublin, Ireland
- UCD Earth Institute, University College Dublin, Dublin, Ireland
| | - Laurence Fitzhenry
- Department of Science, Waterford Institute of Technology, Waterford, Ireland
- Pharmaceutical and Molecular Biotechnology Research Centre (PMBRC), Waterford Institute of Technology, Waterford, Ireland
| | - Carl K.-Y. Ng
- UCD School of Biology and Environmental Science, University College Dublin, Dublin, Ireland
- UCD Centre for Plant Science, University College Dublin, Dublin, Ireland
- UCD Earth Institute, University College Dublin, Dublin, Ireland
| | - Paul F. McCabe
- UCD School of Biology and Environmental Science, University College Dublin, Dublin, Ireland
- UCD Centre for Plant Science, University College Dublin, Dublin, Ireland
- UCD Earth Institute, University College Dublin, Dublin, Ireland
| | - Cara T. Daly
- Department of Science, Waterford Institute of Technology, Waterford, Ireland
- Pharmaceutical and Molecular Biotechnology Research Centre (PMBRC), Waterford Institute of Technology, Waterford, Ireland
- Eco-Innovation Research Centre (EIRC), Waterford Institute of Technology, Waterford, Ireland
| |
Collapse
|
2
|
El Moukhtari A, Cabassa-Hourton C, Farissi M, Savouré A. How Does Proline Treatment Promote Salt Stress Tolerance During Crop Plant Development? FRONTIERS IN PLANT SCIENCE 2020; 11:1127. [PMID: 32793273 PMCID: PMC7390974 DOI: 10.3389/fpls.2020.01127] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/08/2020] [Indexed: 05/20/2023]
Abstract
Soil salinity is one of the major abiotic stresses restricting the use of land for agriculture because it limits the growth and development of most crop plants. Improving productivity under these physiologically stressful conditions is a major scientific challenge because salinity has different effects at different developmental stages in different crops. When supplied exogenously, proline has improved salt stress tolerance in various plant species. Under high-salt conditions, proline application enhances plant growth with increases in seed germination, biomass, photosynthesis, gas exchange, and grain yield. These positive effects are mainly driven by better nutrient acquisition, water uptake, and biological nitrogen fixation. Exogenous proline also alleviates salt stress by improving antioxidant activities and reducing Na+ and Cl- uptake and translocation while enhancing K+ assimilation by plants. However, which of these mechanisms operate at any one time varies according to the proline concentration, how it is applied, the plant species, and the specific stress conditions as well as the developmental stage. To position salt stress tolerance studies in the context of a crop plant growing in the field, here we discuss the beneficial effects of exogenous proline on plants exposed to salt stress through well-known and more recently described examples in more than twenty crop species in order to appreciate both the diversity and commonality of the responses. Proposed mechanisms by which exogenous proline mitigates the detrimental effects of salt stress during crop plant growth are thus highlighted and critically assessed.
Collapse
Affiliation(s)
- Ahmed El Moukhtari
- Sorbonne Université, UPEC, CNRS, IRD, INRA, Institut d’Ecologie et Sciences de l’Environnement de Paris, IEES, Paris, France
- Laboratory of Biotechnology & Sustainable Development of Natural Resources, Polydisciplinary Faculty, Sultan Moulay Slimane University, Beni Mellal, Morocco
| | - Cécile Cabassa-Hourton
- Sorbonne Université, UPEC, CNRS, IRD, INRA, Institut d’Ecologie et Sciences de l’Environnement de Paris, IEES, Paris, France
| | - Mohamed Farissi
- Laboratory of Biotechnology & Sustainable Development of Natural Resources, Polydisciplinary Faculty, Sultan Moulay Slimane University, Beni Mellal, Morocco
| | - Arnould Savouré
- Sorbonne Université, UPEC, CNRS, IRD, INRA, Institut d’Ecologie et Sciences de l’Environnement de Paris, IEES, Paris, France
- *Correspondence: Arnould Savouré,
| |
Collapse
|
3
|
Nahar MNEN, Islam MM, Hoque MA, Yonezawa A, Prodhan MY, Nakamura T, Nakamura Y, Munemasa S, Murata Y. Exogenous proline enhances the sensitivity of Tobacco BY-2 cells to arsenate. Biosci Biotechnol Biochem 2017; 81:1726-1731. [PMID: 28622092 DOI: 10.1080/09168451.2017.1340088] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 05/31/2017] [Indexed: 01/24/2023]
Abstract
Arsenic causes physiological and structural disorders in plants. Proline is accumulated as a compatible solute in plants under various stress conditions and mitigates stresses. Here, we investigated the effects of exogenous proline on tobacco Bright Yellow-2 (BY-2) cultured cells under [Formula: see text] stress. Arsenate did not inhibit BY-2 cell growth at 40 and 50 μM but did it at 60 μM. Proline at 0.5 to 10 mM did not affect the cell growth but delayed it at 20 mM. At 40 μM [Formula: see text], neither 0.5 mM nor 1 mM proline affected the cell growth but 10 mM proline inhibited it. In the presence of [Formula: see text], 10 mM proline increased the number of Evans Blue-stained (dead) cells and decreased the number of total cells. Together, our results suggest that exogenous proline does not alleviate arsenate toxicity but enhances the sensitivity of BY-2 cells to arsenate.
Collapse
Affiliation(s)
- Mst Nur-E-Nazmun Nahar
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | | | - Md Anamul Hoque
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | - Anna Yonezawa
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | - Md Yeasin Prodhan
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | - Toshiyuki Nakamura
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | - Yoshimasa Nakamura
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | - Shintaro Munemasa
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| | - Yoshiyuki Murata
- a Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
| |
Collapse
|
4
|
Mansour MMF, Ali EF. Evaluation of proline functions in saline conditions. PHYTOCHEMISTRY 2017; 140:52-68. [PMID: 28458142 DOI: 10.1016/j.phytochem.2017.04.016] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 02/10/2017] [Accepted: 04/20/2017] [Indexed: 05/20/2023]
Abstract
More than one third of the world's irrigated lands are affected by salinity, which has great impact on plant growth and yield worldwide. Proline accumulation under salt stress has been indicated to correlate with salt tolerance. Exogenous application as well as genetic engineering of metabolic pathways involved in the metabolism of proline has been successful in improving tolerance to salinity. Correlation between proline accumulation as well as its proposed roles and salt adaptation, however, has not been clearly confirmed in several plant species. In addition, the studies relating proline functions and plant salt tolerance are always carried out in growth chambers, and are not successfully verified in field conditions. Further, plant salt tolerance is a complex trait, and studies based solely on proline accumulation do not adequately explain its functions in salinity tolerance, and thus it is difficult to interpret the discrepancies among different data. Moreover, several reports indicate that Pro role in salt tolerance is a matter of debates, as whether Pro accumulation has adaptive significance or is a consequence of alterations in cellular metabolism induced by salinity. As no consensus is obtained on the exact roles of proline production, proline exact roles in the adaptation to saline environments is therefore still lacking and is even a matter of debates. It is obvious that comprehensive future research is needed to establish the proline exact mechanism by which it enhances plant salt tolerance. We propose, however, that proline might be essential for improving salinity tolerance in some species/cultivars, but may not be relevant in others. Evidence supporting both arguments has been presented in order to reassess the feasibility of the proposed roles of Pro in plant salt tolerance mechanism.
Collapse
Affiliation(s)
- Mohamed Magdy F Mansour
- Dept. of Botany, Fac. of Science, Ain Shams Univ., Cairo 11566, Egypt; Dept. of Biology, Fac. of Science, Taif Univ., Taif, Saudi Arabia.
| | - Esmat Farouk Ali
- Dept. of Horticulture (Floriculture), Fac. of Agriculture, Assuit Univ., Assuit, Egypt; Dept. of Biology, Fac. of Science, Taif Univ., Taif, Saudi Arabia
| |
Collapse
|
5
|
Hayat S, Hayat Q, Alyemeni MN, Wani AS, Pichtel J, Ahmad A. Role of proline under changing environments: a review. PLANT SIGNALING & BEHAVIOR 2012; 7:1456-66. [PMID: 22951402 PMCID: PMC3548871 DOI: 10.4161/psb.21949] [Citation(s) in RCA: 966] [Impact Index Per Article: 80.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
When exposed to stressful conditions, plants accumulate an array of metabolites, particularly amino acids. Amino acids have traditionally been considered as precursors to and constituents of proteins, and play an important role in plant metabolism and development. A large body of data suggests a positive correlation between proline accumulation and plant stress. Proline, an amino acid, plays a highly beneficial role in plants exposed to various stress conditions. Besides acting as an excellent osmolyte, proline plays three major roles during stress, i.e., as a metal chelator, an antioxidative defense molecule and a signaling molecule. Review of the literature indicates that a stressful environment results in an overproduction of proline in plants which in turn imparts stress tolerance by maintaining cell turgor or osmotic balance; stabilizing membranes thereby preventing electrolyte leakage; and bringing concentrations of reactive oxygen species (ROS) within normal ranges, thus preventing oxidative burst in plants. Reports indicate enhanced stress tolerance when proline is supplied exogenously at low concentrations. However, some reports indicate toxic effects of proline when supplied exogenously at higher concentrations. In this article, we review and discuss the effects of exogenous proline on plants exposed to various abiotic stresses. Numerous examples of successful application of exogenous proline to improve stress tolerance are presented. The roles played by exogenous proline under varying environments have been critically examined and reviewed.
Collapse
Affiliation(s)
- Shamsul Hayat
- Department of Botany & Microbiology, Faculty of Science, King Saudi University, Riyadh, Saudi Arabia.
| | | | | | | | | | | |
Collapse
|
6
|
Kim Y, Hyun SH, Park HE, Choi HK. Metabolic profiling, free-radical scavenging and tyrosinase inhibitory activities of Lemna minor whole plants cultivated in various concentrations of proline and sucrose. Process Biochem 2012. [DOI: 10.1016/j.procbio.2011.10.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
|
7
|
Heuer B. Role of Proline in Plant Response to Drought and Salinity. HANDBOOK OF PLANT AND CROP STRESS,THIRD EDITION 2010. [DOI: 10.1201/b10329-12] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
8
|
Roosens NH, Willem R, Li Y, Verbruggen I, Biesemans M, Jacobs M. Proline metabolism in the wild-type and in a salt-tolerant mutant of nicotiana plumbaginifolia studied by (13)C-nuclear magnetic resonance imaging. PLANT PHYSIOLOGY 1999; 121:1281-90. [PMID: 10594115 PMCID: PMC59495 DOI: 10.1104/pp.121.4.1281] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/1999] [Accepted: 08/18/1999] [Indexed: 05/20/2023]
Abstract
To obtain insight into the link between proline (Pro) accumulation and the increase in osmotolerance in higher plants, we investigated the biochemical basis for the NaCl tolerance of a Nicotiana plumbaginifolia mutant (RNa) that accumulates Pro. Pro biosynthesis and catabolism were investigated in both wild-type and mutant lines. (13)C-Nuclear magnetic resonance with [5-(13)C]glutamate (Glu) as the Pro precursor was used to provide insight into the mechanism of Pro accumulation via the Glu pathway. After 24 h under 200 mM NaCl stress in the presence of [5-(13)C]Glu, a significant enrichment in [5-(13)C]Pro was observed compared with non-stress conditions in both the wild type (P2) and the mutant (RNa). Moreover, under the same conditions, [5-(13)C]Pro was clearly synthesized in higher amounts in RNa than in P2. On the other hand, measurements of enzyme activities indicate that neither the biosynthesis via the ornithine pathway, nor the catabolism via the Pro oxidation pathway were affected in the RNa mutant. Finally, the regulatory effect exerted by Pro on its biosynthesis was evaluated. In P2 plantlets, exogenous Pro markedly reduced the conversion of [5-(13)C]Glu into [5-(13)C]Pro, whereas Pro feedback inhibition was not detected in the RNa plantlets. It is proposed that the origin of tolerance in the RNa mutant is due to a mutation leading to a substantial reduction of the feedback inhibition normally exerted in a wild-type (P2) plant by Pro at the level of the Delta-pyrroline-5-carboxylate synthetase enzyme.
Collapse
Affiliation(s)
- NH Roosens
- Laboratory of Plant Genetics, Institute of Molecular Biology, Free University of Brussels, Paardenstraat 65, B-1640 Sint-Genesius-Rode, Belgium
| | | | | | | | | | | |
Collapse
|
9
|
Heuer B. Osmoregulatory Role of Proline in Plants Exposed to Environmental Stresses. BOOKS IN SOILS, PLANTS, AND THE ENVIRONMENT 1999. [DOI: 10.1201/9780824746728.ch32] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
|