PYK10, a β‐glucosidase located in the endoplasmatic reticulum, is crucial for the beneficial interaction between Arabidopsis thaliana and the endophytic fungus Piriformospora indica

Abstract

SummaryPiriformospora indica, an endophyte of the Sebacinaceae family, promotes growth and seed production of many plant species, including Arabidopsis. Growth of a T-DNA insertion line in PYK10 is not promoted and the plants do not produce more seeds in the presence of P. indica, although their roots are more colonized by the fungus than wild-type roots. Overexpression of PYK10 mRNA did not affect root colonization and the response to the fungus. PYK10 codes for a root-and hypocotyl-specific b-glucosidase/myrosinase, which is implicated to be involved in plant defences against herbivores and pathogens. Expression of PYK10 is activated by the basic helix-loop-helix domain containing transcription factor NAI1, and two Arabidopsis lines with mutations in the NAI1 gene show the same response to P. indica as the PYK10 insertion line. PYK10 transcript and PYK10 protein levels are severely reduced in a NAI1 mutant, indicating that PYK10 and not the transcription factor NAI1 is responsible for the response to the fungus. In wild-type roots, the message level for a leucine-rich repeat protein LRR1, but not for plant defensin 1.2 (PDF1.2), is upregulated in the presence of P. indica. In contrast, in lines with reduced PYK10 levels the PDF1.2, but not LRR1, message level is upregulated in the presence of the fungus. We propose that PYK10 restricts root colonization by P. indica, which results in the repression of defence responses and the upregulation of responses leading to a mutualistic interaction between the two symbiotic partners.

Endolichenic fungi: the lesser known fungal associates of lichens

“…While endophyte assemblage in plants is influenced by the age and chemistry of the host tissue (Arnold and Herre 2003; Suryanarayanan and Thennarasan 2004), it is not known if the age and chemical composition of a lichen influences the density of colonisation and species composition of its endolichenic fungi. Endophytes increase the ecological fitness of their host plants by making them more tolerant to abiotic stress including drought, salinity and high temperature (Sherameti et al 2008; Sun et al 2010). Such increased host fitness is achieved at least in a few cases by endophyte-mediated induction of stress-related host genes (Sherameti et al 2008).…”

“…Endophytes increase the ecological fitness of their host plants by making them more tolerant to abiotic stress including drought, salinity and high temperature (Sherameti et al 2008; Sun et al 2010). Such increased host fitness is achieved at least in a few cases by endophyte-mediated induction of stress-related host genes (Sherameti et al 2008). Endophytes could also enhance a plant’s abiotic stress tolerance by altering its growth hormone metabolism (Khan et al 2015).…”

Do ethylene response factorS9 and -14 repress PR gene expression in the interaction between Piriformospora indica and Arabidopsis?

“…Mutualism or parasitism is directly connected to defense gene expression, which affects microbial growth and root colonization. 1,4,25 In addition, PR-1 expression is constitutively downregulated in ERF14, but not in ERF9 roots when compared to the wildtype, independent of fungal colonization (Fig. 4).…”

Functions of Novel Symbiotic Fungus - Piriformospora Indica

“…Apparently, P. indica -A. thaliana interaction represents a novel type of beneficial fungus-root interaction with early protein alterations in the plasma membrane and the endoplasmic reticulum [2,4]. In A. thaliana, pronounced plant growth promotion and enhanced seed production were noticed in the presence of P. indica, involving synthesis of a leucine-rich protein repeat [17,18], increased expression of nitrate reductase and a starch-degrading enzyme [18] as well as expression of a ß-glucosidase in the endoplasmic reticulum [19]. In addition, changes in levels of auxins and cytokinins were noticed [20].…”