Induced resistance triggered byPiriformospora indica

Abstract

ling, ISR by contrast often relies on an enhancement of jasmonate (JA)-and/or ethylene (ET)-dependent defence. 7,8 Both mechanisms require the key regulator Non-expressor-of-PR-genes 1 (NPR1) though the biochemical mechanisms involving this protein are different in SAR and ISR. 9 The here described root endophytic fungus Piriformospora indica belongs to the order Sebacinales (Basidiomycota) 10 and forms a mutualistic symbiosis with a broad spectrum of host plants, such as barley, maize, Arabidopsis, tomato and tobacco. [11][12][13] In barley the fungus induces resistance to root diseases and leads to systemic protection against powdery mildew caused by Blumeria graminis f. sp. hordei. 14,15 Lately, we showed that P. indica similarly induces systemic resistance to Golovinomyces orontii in Arabidopsis. 16 P. indica Induced Resistance Resembles ISRP. indica-mediated resistance in Arabidopsis against the powdery mildew G. orontii shows clear parallels to JA and ET requiring ISR. 16 The jasmonate-insensitive mutants jasmonate-resistant 1 (jar1-1) 17 and jasmonate-insensitive 1 (jin 1) 18 as well as the null mutant npr1-1 [Nonexpressor of pathogenesis-related (PR) genes 1, also known as NIM1] 19 are compromised in P. indica-mediated resistance. All these mutants define genes known to be involved in JA signaling. By contrast, NahG plants expressing a bacterial salicylate-hydroxylase 20 and the npr1-3 mutant, lacking the nuclear-localisation signal, were not affected in P. indica mediated resistance to G. orontii. Both of them are defective in salicylate-governed SAR. Hence, P. indica induced systemic resistance against powdery mildew requires the transcriptional regulator JIN1/AtMYC2, the JA signalling component JAR1 (a JA-amino synthetase) 21 and the cytosolic function of NPR1, but does not require elevated SA levels nor the nuclear function of NPR1 (which is compromised in npr1-1 but not in npr1-3). Thus, the mutational analysis suggests that P. indica exploits mechanism known for ISR.ISR is accompanied by a rather weak or even not detectable systemic up or downregulation of transcripts in the absence of a challenging pathogen. 22,23 Accordingly, leaves of P. indica colonized and non-colonized plants showed comparable, non-induced levels of SA-, JA-and ET-responsive genes. 16 Only after powdery mildew challenge a stronger expression of the JA-inducible vegetative storage protein gene VSP1 was observed exclusively in P. indica colonized plants. A similar response of Arabidopsis was described for a vegetative storage protein during rhizobacteria-induced ISR. 24 The stronger VSP1 induction in P. indica colonized plants after pathogen challenge not only substantiates the role of JA in P. indica induced resistance. It also [Plant Signaling & Behavior 4:3, 215-216; March 2009] ; ©2009 Landes BioscienceThe root endophytic Basidiomycete Piriformospora indica forms a specific type of mycorrhiza symbiosis with a broad spectrum of plant species, including the Brassicaceae. A recent report on the interaction of P. indica with Ar...

Arabidopsis thaliana model system reveals a continuum of responses to root endophyte colonization

“…Arabidopsis thaliana is non-mycorrhizal and no natural root mutualisms had been reported until it was shown to benefit from an association with a soil-inhabiting basidiomycete, Piriformospora indica Verma, Varma, Rexer, Kost & Franken (Peškan-Beghöfer et al 2004). In laboratory studies, this fungus often improved plant growth or fitness, increased drought and biotic stress tolerance, and induced disease resistance (Waller et al 2005, Shahollari et al 2007, Shermati et al 2008a, Stein et al 2008, Molitor & Kogel 2009, Vandassery & Oelmüller 2009, Zuccaro et al 2009, Molitor et al 2011, Hilbert et al 2012. These results have led to the conclusion that P. indica forms mutualisms with a range of hosts including A. thaliana and bears a promise to be exploited in crop protection (Qiang et al 2012a).…”

Comparative analysis of BABA and Piriformospora indica mediated priming of defence-related genes in tomato against early blight

“…Similarly, selected strains of non-pathogenic plant growthpromoting rhizobacteria (PGPR) are also known to enhance defence capacity of plants that is commonly referred to as ISR [2]. Recently discovered mycorrhiza like root-endophyte Piriformospora indica [13] is also reported to confer resistance against biotic [14] and abiotic stresses [15,16] in the host plants. Studies have demonstrated that P. indica improves resistance in several crop plants against a wide range of pathogens [17,18].…”

Enigmatic Sebacinales

“…Otherwise, the broad experimental host range of angiosperms (e.g. Varma et al 2001;Molitor and Kogel 2009), could not have been applied in experimental studies (see Sebacinalean endophytes). So far, there are no plant species known that cannot be colonized by P. indica (Klute 2011), the 145 tested until 2009 ) referring exclusively to experimental approaches.…”