The oomycete microbe-associated molecular pattern Pep-13 triggers SERK3/BAK1-independent plant immunity
Oomycetes MAMP Pep-13 can trigger SERK3/BAK1-independent PTI. Silencing of SERK3/BAK1 in solanaceous plants resulted in reduced expression of brassinosteroid marker genes and enhanced PTI transcriptional responses to Pep-13 treatment.
To prevent disease, pattern recognition receptors (PRRs) are responsible for detecting microbe-associated molecular patterns (MAMPs) to switch on plant innate immunity. SOMATIC EMBROYOGENESIS KINASE 3 (SERK3)/BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1) is a well-characterized receptor-like kinase (RLK) that serves as a pivotal co-receptor with PRRs to activate immunity following recognition of MAMPs including flg22, EF-Tu, INF1 and XEG1. However, the requirement for SERK3/BAK1 in many pattern-triggered immune (PTI) signaling pathways is not yet known. Pep-13 is an oomycete MAMP that consists of a highly conserved motif (an oligopeptide of 13 amino acids) shared in Phytophthora transglutaminases. Quantitative RT-PCR analysis reveals that the transcripts of three PTI marker genes (WRKY7, WRKY8 and ACRE31) rapidly accumulate in response to three different MAMPs: flg22, chitin and Pep-13. Whereas silencing of SERK3/BAK1 in Nicotiana benthamiana or potato compromised transcript accumulation in response to flg22, it did not attenuate WRKY7, WRKY8 and ACRE31 up-regulation in response to chitin or Pep-13. This indicates that Pep-13 triggers immunity in a SERK3/BAK1-independent manner, similar to chitin. Surprisingly, silencing of SERK3/BAK1 led to significantly increased accumulation of PTI marker gene transcripts following Pep-13 or chitin treatment, compared to controls. This was accompanied by reduced expression of brassinosteroid (BR) marker genes StSTDH, StEXP8 and StCAB50 and StCHL1, which is a negative regulator of PTI, supporting previous reports that SERK3/BAK1-dependent BR signaling attenuates plant immunity. We provide Pep-13 as an alternative to chitin as a trigger of SERK3/BAK1-independent immunity.
KeywordsMAMP Disease resistance Transcriptome Flagellin Late blight
Pattern recognition receptors
Microbe-associated molecular patterns
BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1
This work was support by the National Natural Science Foundation of China (31761143007, 31171603) and the Fundamental Research Funds for the Central Universities (2662017PY069) for funding ZT’s lab. We thank the Biotechnology and Biological Sciences Research Council (BBSRC) for funding PRJB’s lab (BB/L026880/1).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Albrecht C, Boutrot F, Segonzac C, Schwessinger B, Gimenez-Ibanez S, Chinchilla D, Rathjen JP, de Vries SC, Zipfel C (2012) Brassinosteroids inhibit pathogen-associated molecular pattern-triggered immune signaling independent of the receptor kinase BAK1. Proc Natl Acad Sci USA 109:303–308CrossRefGoogle Scholar
- Chaparro-Garcia A, Wilkinson RC, Gimenez-Ibanez S, Findlay K, Coffey MD, Zipfel C, Rathjen JP, Kamoun S, Schornack S (2011) The receptor-like kinase SERK3/BAK1 is required for basal resistance against the late blight pathogen Phytophthora infestans in Nicotiana benthamiana. PloS One 6:e16608CrossRefGoogle Scholar
- Du J, Verzaux E, Chaparro-Garcia A, Bijsterbosch G, Keizer LC, Zhou J, Liebrand TW, Xie C, Govers F, Robatzek S, van der Vossen EA, Jacobsen E, Visser RG, Kamoun S, Vleeshouwers VG (2015) Elicitin recognition confers enhanced resistance to Phytophthora infestans in potato. Nat Plants 1:15034CrossRefGoogle Scholar
- McLellan H, Boevink PC, Armstrong MR, Pritchard L, Gomez S, Morales J, Whisson SC, Beynon JL, Birch PRJ (2013) An RxLR effector from Phytophthora infestans prevents re-localisation of two plant NAC transcription factors from the endoplasmic reticulum to the nucleus. PLoS Pathog 9:e1003670CrossRefGoogle Scholar