Novel Symbiotrophic Endophytes
Endophytes are microorganisms that reside in the tissues of living plants without causing any immediate overt negative effect (Bacon and White 2000). Of the nearly 300,000 plants species that exist on the earth, each individual plant is host to one or mor
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Introduction
Endophytes are microorganisms that reside in the tissues of living plants without causing any immediate overt negative effect (Bacon and White 2000). Of the nearly 300,000 plants species that exist on the earth, each individual plant is host to one or more endophytes (Strobel and Daisy 2003). These endophytes are relatively unstudied and are potential sources of novel natural products for exploitation in medicine, agriculture, and industry. Very few of these endophytes have been studied to date, and this opens a new opportunity to find out novel endophytes in myriads of ecological niches. One of the important facets of these endophytes is their evolution with plants over a period of millennia that makes them live in a symbiotrophic relationship in such a way that both becomes indispensible to each other. While the symptomless nature of endophyte occupation in plant tissue has prompted the focusing on symbiotic or mutualistic relationships between endophytes and their hosts, the observed biodiversity of endophytes suggests they can also be aggressive saprophytes or opportunistic pathogens (Strobel and Daisy 2003). The most common endophytes of plants are bacteria and fungi, but evidence indicates that other life forms like viruses exist in plants as endophytes (Marquez et al. 2007). The most frequently isolated endophytes are the fungi (Hawksworth and Rossman 1987). Dreyfuss and Chapela (1994) estimated that there may be at least 1 million species of endophytic fungi alone. It can be readil concluded that majority of these endophytes are symbiotic and can have tremendous applications in the area of drug discovery, medicine and agriculture.
Amit C. Kharkwal Amity Institute of Microbial Technology, Amity University Uttar Pradesh, Block ‘A’ Sector 125, Noida 201 303 e-mail: [email protected]
A. Varma (ed.) Mycorrhiza, © Springer-Verlag Berlin Heidelberg 2008
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2 Strategy for Endophyte Discovery Several reasonable hypotheses (Strobel and Daisy 2003) govern the plant selection strategy for selection of novel symbiotrophic endophytes and these are: 1. Plants from extreme environmental settings and with unusual biology possessing novel strategies for survival. 2. Plants having ethnobotanical history. The healing source may reside in the endophyte. 3. Plants which have unusual longevity are more likely to be lodged with endophytes possessing natural products. 4. Plants living in the areas with high biodiversity also have the prospect of housing novel endophytes
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Extreme Environments and Endophytes Discovery
Extreme environmental conditions and unusual plant biology offers great opportunities for the discovery of novel symbiotrophic endophytes (Rodriguez et al. 2004a). For example, Piriformospora indica, a novel multifunctional symbiotrophic fungal endophyte (Verma et al. 1998) was discovered from the Great Indian Desert of Western Rajasthan in India. The fungus was found to colonize roots of the desert plants which were growing in extreme conditions of water scarcit
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