Sm2, a paralog of the Trichoderma cerato-platanin elicitor Sm1, is also highly important for plant protection conferred by the fungal-root interaction of Trichoderma with maize

Abstract

BackgroundThe proteins Sm1 and Sm2 from the biocontrol fungus Trichoderma virens belong to the cerato-platanin protein family. Members of this family are small, secreted proteins that are abundantly produced by filamentous fungi with all types of life-styles. Some species of the fungal genus Trichoderma are considered as biocontrol fungi because they are mycoparasites and are also able to directly interact with plants, thereby stimulating plant defense responses. It was previously shown that the cerato-platanin protein Sm1 from T. virens - and to a lesser extent its homologue Epl1 from Trichoderma atroviride - induce plant defense responses. The plant protection potential of other members of the cerato-platanin protein family in Trichoderma, however, has not yet been investigated.ResultsIn order to analyze the function of the cerato-platanin protein Sm2, sm1 and sm2 knockout strains were generated and characterized. The effect of the lack of Sm1 and Sm2 in T. virens on inducing systemic resistance in maize seedlings, challenged with the plant pathogen Cochliobolus heterostrophus, was tested. These plant experiments were also performed with T. atroviride epl1 and epl2 knockout strains. In our plant-pathogen system T. virens was a more effective plant protectant than T. atroviride and the results with both Trichoderma species showed concordantly that the level of plant protection was more strongly reduced in plants treated with the sm2/epl2 knockout strains than with sm1/epl1 knockout strains.ConclusionsAlthough the cerato-platanin genes sm1/epl1 are more abundantly expressed than sm2/epl2 during fungal growth, Sm2/Epl2 are, interestingly, more important than Sm1/Epl1 for the promotion of plant protection conferred by Trichoderma in the maize-C. heterostrophus pathosystem.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0333-0) contains supplementary material, which is available to authorized users.

Overexpression of MoSM1, encoding for an immunity-inducing protein from Magnaporthe oryzae, in rice confers broad-spectrum resistance against fungal and bacterial diseases

“…Indeed, a number of CPs from different filamentous fungi, e.g. SM1, SM2 and Epl1 from the biocontrol agents T. virens and T. atroviride 37404547 as well as BcSpl1 from B. cinerea and a CP from C. platani 2944, were shown to induce both local and systemic disease resistance in host and nonhost plants against different life style pathogens. In the present study, we found that overexpression of MoSM1 in transgenic rice plants confers an improved resistance against two strains representing difference races of M. oryzae and Xoo , as revealed by reduced disease severity and suppressed in planta pathogen growth (Figs 3 and 4).…”

“…For example, BcSpl1 in Botrytis cinerea and MoMSP1 in Magnaporthe oryzae were found to contribute to the fungal virulence as the knock-out mutants for BcSpl1 or MoMSP1 showed reduced virulence in their host plants303132. Meanwhile, it has also been shown that CPs from both pathogenic and beneficial biocontrol fungi can induce locally and systemically some structural, physiological and molecular defense responses, including initiation of hypersensitive response (HR), accumulation of phenolic compounds and phytoalexins, production of reactive oxygen species (ROS), and upregulation of defense-related genes in host and nonhost plants33343536373839404142434445. SM1 and SM2 from Trichoderma virens , BcSpl1 from B. cinerea , and MoSM1 (also known as MoMSP1) from M. oryzae could induce systemic disease resistance in rice, cotton, maize, tobacco, tomato and Arabidopsis against different pathogens3237384042454647 and the activation of systemic resistance by CP from C. platani and BcSpl1 from B. cinerea was found to be regulated through stomatal perception, overexpression of salicylic acid (SA)- and ethylene-signaling genes and camalexin biosynthesis4446.…”

The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species

“…Despite the fact that CPs are highly represented in fungal genomes, their primary function is not entirely clear, but some species have been demonstrated to be involved as virulence factors or elicitors during plant-pathogenic and symbiotic interactions, respectively. For example, during the mutualistic T. virens-plant interaction, fungal CP elicitors Sm1 (TR_82662, TA_302952, and TV_110852) and Sm2 (TR_123955, TA_88590, and TV_111830) are secreted during the first stages of root sensing and induce systemic disease resistance, conferring resistance to phytopathogens (28,29,1271,1272). In contrast, CP virulence factor BcSpl1 from Botritys cinerea has a phytotoxic function in inducing necrosis on tobacco leaves (1273).…”

The fungal cerato-platanin protein EPL1 forms highly ordered layers at hydrophobic/hydrophilic interfaces

“…27,28 Whether this is solely due to the fact that CPPs such as EPL1 or SM1 effectively signal the presence of a fungus for plants or whether CPPs are directly involved in the physical interaction of fungal hyphae with plant roots remains to be investigated. for epl1 gene knockout strains so far no growth defects or phenotypes related to the formation of hyphae or spores were detected, also not during stress growth conditions such as osmotic stress.…”