Fungal Endophytes: Drought Tolerance in Plants: Difference between revisions
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====Class 3 and 4==== | ====Class 3 and 4==== | ||
<br>Class 3 colonizes the shoot of plants while Class 4 colonizes plant roots.[[#References |[4]]] Few studies have been performed on Classes 3 and 4 endophytes, and little is known about their ecological role and their ability to confer tolerance. | <br>Class 3 colonizes the shoot of plants while Class 4 colonizes plant roots.[[#References |[4]]] Few studies have been performed on Classes 3 and 4 endophytes, and little is known about their ecological role and their ability to confer tolerance. | ||
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Redman et al (2015) examined the osmotic concentrations in non symbiotic and heat-stress tolerant symbiotic plants. The pattern was different between the two groups, leading them to conclude that symbiotic plants do not only rely on increasing their osmolyte concentrations.[[#References |[6]]] | |||
An early response to stress is the generation of reactive oxygen species. [[#References |[6]]] | |||
While fungal endophytes show habitat-adapted symbiosis, the fact that there is still lower biodiversity in high stress environments indicates that more is needed. [[#References |[6]]] | |||
Schardl, C. L., Leuchtmann, A. & Spiering, M. J. (2004) Annu. Rev. Plant Biol. 55, 315-340. [PubMed] | |||
fungal loline alkaloids, which are abundant in those symbiota for which the endophyte has a documented and consistent positive effect on drought tolerance | |||
being nontoxic to plant cells, highly water soluble, and generally increasing in response to heat or drought. However, it is unclear if lolines reach sufficient levels to significantly affect osmotic balance. | |||
If these alkaloids are involved, they might protect macromolecules from denaturation and/or scavenge reactive oxygen species associated with drought stress, possibilities not yet tested. | |||
Redman RS, Kim YO, Woodward CJDA, Greer C, Espino L, Doty SL, Rodriguez RJ. | |||
2011. Increased fitness of rice plants to abiotic stress via habitat adapted | |||
symbiosis: A strategy for mitigating impacts of climate change. PLoS One | |||
6(7):e14823. | |||
Figure** | |||
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130040/ | |||
The class 2 fungal endophytes Fusarium culmorum and Curvularia protuberata made plants grown in both a greenhouse and growth chambers more tolerant to salt, drought and cold. Plants not grown in stressful environments showed no negative costs to having endophytes. Plants with endophytes grown in stressful environments reduced their water consumption by 20–30% while their growth rate, reproductive yield, and biomass increased. Plants without the fungal endophytes experienced decreases in shoot and root biomass when exposed to stress. This article quantifies the tolerance that these fungal endophytes confer to their hosts and discusses the importance of the results to increasing agricultural productivity. However, a limitation of this article is that the mechanism of the conferred drought tolerance is not known. | |||
Reduced water consumption by 20-30%, increased growth rate, reproductive yield, biomass | |||
Colonization decreased to 65% in absence of stress | |||
Plants perceive, transmit signals, and respond to abiotic stresses such as drought, heat and salinity | |||
High stress habitats have lower plant abundance | |||
Class 2 fungal endophytes | |||
Habitat Adapted Symbiosis | |||
Class 2 endophytes can colonize and confer tolerance to monocot and eudicot plants so may predate the diverance of the two (est. 145-230) | |||
Salty water from tidal wave and tidal surge after cyclone in Indonesia and Burma, increased min air temp in China and Philippines | |||
Test 3 endophytes and their influence on rice | |||
Analyzed levels of osmolytes – increase production as response to salt stress and ROS | |||
SaltSym from Leymus mollis – costal plant exposed to high salt stress | |||
TempSym 1 and 2 from Dichanthelium lanuginosum in geothermal soils – both conferred cold tolerance, reg early events in temp stress response | |||
All species in the family Poacea but different subfamilies | |||
Symbiotic communication needed for tolerance in conserved | |||
All 3 delayed wilt 2-3 times beyond that of NS plants, correlated with reduction of water usage 20-30% | |||
ROS – only a max of 22% of leaf photobleached in S as compared to 100% in NS | |||
Endophytes influence allocation of resources in roots and shoots (enhanced growth within 24 hours), increased root mass prior to shoot growth while NS shoots first --> | |||
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|[5] [http://www.sciencedirect.com/science/article/pii/S0031942206006522 Koulman, Albert, et al. "Peramine and Other Fungal Alkaloids are Exuded in the Guttation Fluid of Endophyte-Infected Grasses." Phytochemistry 68.3 (2007): 355-60. Print.]<br> | |[5] [http://www.sciencedirect.com/science/article/pii/S0031942206006522 Koulman, Albert, et al. "Peramine and Other Fungal Alkaloids are Exuded in the Guttation Fluid of Endophyte-Infected Grasses." Phytochemistry 68.3 (2007): 355-60. Print.]<br> | ||
|[6] [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130040/ Redman, Regina S. et al. “Increased Fitness of Rice Plants to Abiotic Stress Via Habitat Adapted Symbiosis: A Strategy for Mitigating Impacts of Climate Change.” Ed. Hany A. El-Shemy. PLoS ONE 6.7 (2011): e14823. PMC. Web. 24 Mar. 2015.] | |[6] [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130040/ Redman, Regina S. et al. “Increased Fitness of Rice Plants to Abiotic Stress Via Habitat Adapted Symbiosis: A Strategy for Mitigating Impacts of Climate Change.” Ed. Hany A. El-Shemy. PLoS ONE 6.7 (2011): e14823. PMC. Web. 24 Mar. 2015.] | ||
|[7] [http://www.annualreviews.org/doi/full/10.1146/annurev.arplant.55.031903.141735?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed Schardl, C. L., Leuchtmann, A. & Spiering, M. J. (2004) Annu. Rev. Plant Biol. 55, 315-340. ] | |||
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Revision as of 15:31, 24 March 2015
It has been estimated that over 80% of terrestrial plants form a symbiotic association with fungi.[1] Fungal endophytes have played an essential role in the evolution of land plants and remain an important component of terrestrial ecosystems. In these mutualistic associations, fungi may benefit their host plant by acquiring nutrients, increasing plant biomass, and conferring tolerance to biotic and abiotic stresses. Studies show that symbiotic fungi can enhance drought, salt, and soil temperature tolerance of their host plant in addition to increasing its resistance to parasitic fungi and herbivores. These habitat-adapted symbioses enable plants to thrive in harsh conditions where they would otherwise not be able to grow.
It is hypothesized that phototroph-fungi associations enabled plants to first colonize land. The mutualistic association of algae and fungi could have helped them avoid desiccation, damaging solar radiation, and more extreme temperatures.[2] Fungal endophytes today colonize a variety of both monocot and eudicot plants which suggests this symbiosis predates the monocot-dicot split that occured 140-150 Myr ago.[3]
Fungal endophytes have many potential applications in agriculture and conservation, yet there is still much that is not known about plant-fungi symbiosis and the mechanisms behind it. Fungal endophytes alter plants’ growth, development, and root morphology to reduce water consumption and increase nutrient uptake. This may be used to increase crop yield in arid climates and mitigate the negative effects of climate change.
Classes of Fungal Endophytes
Clavicipitaceous Endophytes (C-endophytes)
Class 1
C-endophytes infect the plant shoots of some grasses, form systemic intercellular infections, and are passed on through vertical and horizontal transmission.[4] Many produce alkaloids to protect their host plant from herbivory by insects and mammals, and studies have shown them to confer drought and metal tolerance.[4][5] Endophytes may increase the development of root systems or the length of root hairs.[4]
Nonclavicipitaceous Endophytes (NC-endophytes)
Class 2
Class 2 endophytes are usually found in the roots, stem, or leaves of their hosts.[4] They can be transmitted either vertically through the seed coat or horizontally. [4] They can confer habitat-specific stress tolerance to their hosts, and they infect a higher percentage of plants in high-stress environments.[4]
Class 3 and 4
Class 3 colonizes the shoot of plants while Class 4 colonizes plant roots.[4] Few studies have been performed on Classes 3 and 4 endophytes, and little is known about their ecological role and their ability to confer tolerance.
]
Further Reading
[Sample link] Ebola Hemorrhagic Fever—Centers for Disease Control and Prevention, Special Pathogens Branch-->
References
|[1][Smith, S., Read, D., 1997: Mycorrhizal symbiosis, 2nd edn., Academy Press, San Diego. ]
|[2]Selosse, M-A, and F. Le Tacon. "The Land Flora: A Phototroph-Fungus Partnership?" Trends in Ecology & Evolution 13.1 (1998): 15-20. Print.
|[3] Shu-Miaw C., Chien-Chang C., Hsin-Liang C., Wen-Hsiung L."Dating the Monocot–Dicot Divergence and the Origin of Core Eudicots Using Whole Chloroplast Genomes". "Journal of Molecular Evolution". 2004. Volume 58, p. 424-441
|[4]Rodriguez, R. J., et al. "Fungal Endophytes: Diversity and Functional Roles." New Phytologist 182.2 (2009): 314-30. Print.
|[5] Koulman, Albert, et al. "Peramine and Other Fungal Alkaloids are Exuded in the Guttation Fluid of Endophyte-Infected Grasses." Phytochemistry 68.3 (2007): 355-60. Print.
|[6] Redman, Regina S. et al. “Increased Fitness of Rice Plants to Abiotic Stress Via Habitat Adapted Symbiosis: A Strategy for Mitigating Impacts of Climate Change.” Ed. Hany A. El-Shemy. PLoS ONE 6.7 (2011): e14823. PMC. Web. 24 Mar. 2015.
|[7] Schardl, C. L., Leuchtmann, A. & Spiering, M. J. (2004) Annu. Rev. Plant Biol. 55, 315-340.
Edited by (Sarah Barnes), a student of Nora Sullivan in BIOL168L (Microbiology) in The Keck Science Department of the Claremont Colleges Spring 2014.
