Aberrant Synthesis of Indole-3-Acetic Acid in Saccharomyces cerevisiae Triggers Morphogenic Transition, a Virulence Trait of Pathogenic Fungi

Department of Biology and Biotechnology, Life Sciences and Bioengineering Center at Gateway Park, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01605, USA.
Genetics (Impact Factor: 5.96). 03/2010; 185(1):211-20. DOI: 10.1534/genetics.109.112854
Source: PubMed


Many plant-associated microbes synthesize the auxin indole-3-acetic acid (IAA), and several IAA biosynthetic pathways have been identified in microbes and plants. Saccharomyces cerevisiae has previously been shown to respond to IAA by inducing pseudohyphal growth. We observed that IAA also induced hyphal growth in the human pathogen Candida albicans and thus may function as a secondary metabolite signal that regulates virulence traits such as hyphal transition in pathogenic fungi. Aldehyde dehydrogenase (Ald) is required for IAA synthesis from a tryptophan (Trp) precursor in Ustilago maydis. Mutant S. cerevisiae with deletions in two ALD genes are unable to convert radiolabeled Trp to IAA, yet produce IAA in the absence of exogenous Trp and at levels higher than wild type. These data suggest that yeast may have multiple pathways for IAA synthesis, one of which is not dependent on Trp.

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    • "Recently, Rao et al. (2010) showed that IAA stimulated filamentation in Candida albicans. However, a high concentration of IAA was found to inhibit cell growth. "
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    ABSTRACT: Indole 3-acetic acid (IAA) is the principal hormone which regulates various developmental and physiological processes in plants. IAA production is considered as a key trait for supporting plant growth. Hence, in this study, production of indole-3-acetic acid (IAA) by a basidiomycetous red yeast Rhodosporidium paludigenum DMKU-RP301 (AB920314) was investigated and improved by the optimization of the culture medium and culture conditions using one factor at a time (OFAT) and response surface methodology (RSM). The study considered the effects of incubation time, carbon and nitrogen sources, growth factor, tryptophan, temperature, shaking speed, NaCl and pH, on the production of IAA. The results showed that all the factors studied, except NaCl, affected IAA production by R. paludigenum DMKU-RP301. Maximum IAA production of 1,623.9 mg/l was obtained as a result of the studies using RSM. The optimal medium and growth conditions observed in this study resulted in an increase of IAA production by a factor of up to 5.0 compared to the unoptimized condition, i.e. when yeast extract peptone dextrose (YPD) broth supplemented with 0.1% l-tryptophan was used as the production medium. The production of IAA was then scaled up in a 2-l stirred tank fermenter, and the maximum IAA of 1,627.1 mg/l was obtained. This experiment indicated that the obtained optimal medium and condition (pH and temperature) from shaking flask production can be used for the production of IAA in a larger size production. In addition, the present research is the first to report on the optimization of IAA production by the yeast Rhodosporidium.
    The Journal of General and Applied Microbiology 04/2015; 61(1):1-9. DOI:10.2323/jgam.61.1 · 0.94 Impact Factor
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    • "Our results are in agreement with other studies. The accumulation of IAA by Saccharomyces cerevisiae reached its highest level after cultures entered stationary phase (Rao et al. 2010). It was shown that endophytic yeasts genus Rhodotorula produced maximum IAA at 7 d (Xin et al. 2009). "
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    ABSTRACT: 538 yeast strains were isolated from dark chestnut soil collected from under the plants of the legume family (Fabaceae). The greatest number of microorganisms is found at soil depth 10-20cm. Among the 538 strains of yeast 77 (14.3%) strains demonstrated the ability to synthesize IAA. 15 strains were attributed to high IAA-producing yeasts (above 10μg/ml). The most active strains were YA05 with 51.7±2.1μg/ml of IAA and YR07 with 45.3±1.5μg/ml. In the study of effect of incubation time on IAA production the maximum accumulation of IAA coincided with maximum rates of biomass: at 120h for YR07 and at 144h for strain YA05. IAA production increased when medium was supplemented with the l-tryptophan. 400μg/ml of l-tryptophan showed maximum IAA production. 10 strains demonstrated the ability to inhibit the growth and development of phytopathogenic fungi. YA05 and YR07 strains formed the largest zones of inhibition compared to the other strains - from 21.6±0.3 to 30.6±0.5mm. Maximum zone of inhibition was observed for YA05 against Phytophtora infestans and YR07 strains against Fusarium graminearum. YA05 and YR07 strains were identified as Aureobasidium pullulans YA05 (GenBank accession No JF160955) and Rhodotorula mucilaginosa YR07 (GenBank accession No JF160956). Copyright © 2015 Elsevier GmbH. All rights reserved.
    Microbiological Research 03/2015; 175. DOI:10.1016/j.micres.2015.03.008 · 2.56 Impact Factor
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    • "In addition, a TRP-independent IAA biosynthetic pathway has been shown recently in yeast (Rao et al., 2010). So far, only a few fungal genes involved in IAA production have been functionally characterized, and these include the tryptophan aminotransferase (Tam) and aldehyde dehydrogenase (Adh) genes from U. maydis and the aromatic aminotransferases (Aro8 and Aro9) from Saccharomyces cerevisiae (Basse et al., 1996; Robinson et al., 1998; Reineke et al., 2008; Rao et al., 2010). "
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    ABSTRACT: Beneficial effects elicited by the root endophyte Piriformospora indica are widely known, but the mechanism by which these are achieved is still unclear. It is proposed that phytohormones produced by the fungal symbiont play a crucial role in the interaction with the plant roots. Biochemical analyses of the underlying biosynthetic pathways for auxin production have shown that, on tryptophan feeding, P. indica can produce the phytohormones indole-3-acetic acid (IAA) and indole-3-lactate (ILA) through the intermediate indole-3-pyruvic acid (IPA). Time course transcriptional analyses after exposure to tryptophan designated the piTam1 gene as a key player. A green fluorescence protein (GFP) reporter study and transcriptional analysis of colonized barley roots showed that piTam1 is induced during the biotrophic phase. Piriformospora indica strains in which the piTam1 gene was silenced via an RNA interference (RNAi) approach were compromised in IAA and ILA production and displayed reduced colonization of barley (Hordeum vulgare) roots in the biotrophic phase, but the elicitation of growth promotion was not affected compared with the wild-type situation. Our results suggest that IAA is involved in the establishment of biotrophy in P. indica-barley symbiosis and might represent a compatibility factor in this system.
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