PAMP Signaling in Plant Innate Immunity - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 64

2.13 PAMP Triggers Increased Transcription of PRR Gene

and Accumulation of PRR Protein

2.13.1 PAMPs Activate Expression of Genes Encoding PRRs

PAMPs activate the expression of genes encoding various PRRs. The PAMPs
NLP Pp (from oomycete) and Flg22 (from bacteria) induced expression of the recep-
tor genes in plants. They induced several folds the expression of receptor-like
kinases such as lectin RLKs, S-locus RLKs, LRR-RLKs, wall-associated kinases,
receptor protein kinase, and receptor Ser/Thr kinase in A. thaliana (Qutob et al.
2006 ). The LPS from Burkholderia cepacia up-regulated the gene encoding a
receptor-like protein kinase (Sanabria and Dubery 2006 ). Many Arabidopsis genes
encoding RLK and RLP were found to be induced by Flg22 or EF-Tu treatment
(Zipfel et al. 2004 ). Chitin treatment activated the expression of LysM receptor
kinase gene family (17 genes) in Lotus japonica (Lohmann et al. 2010 ). WAK1
was up-regulated upon perception of its own ligand, similarly to what has been
shown for FLS2 and EFR (Brutus et al. 2010 ). Out of a total 216 LRR-RLK in
Arabidopsis , 27 were found to be transcriptionally induced upon treatment with
Flg22 or EF-Tu (Zipfel et al. 2006 ). These results suggest that PAMPs trigger
enhanced expression of several PRRs (Table 2.5 ).

2.13.2 PRRs Are Activated by Widely Varying PAMPs

FLS2 and EFR are induced also by bacterial LPS, fungal chitin, and the oomycete-
derived NPP1 (Zipfel et al. 2006 ). Overall, these different PAMPs seem to trigger
changes in a common set of genes, indicating that plants do not distinguish bacteria,
fungi, and oomycetes on the basis of the signaling signature of their PAMPs. Rather,

Table 2.5 PAMP-triggered upregulation of expression of PRR genes
PAMP Upregulated gene Fold increase in expression References

Flg22 FLS2 2.0 Denoux et al. ( 2008 )

Receptor kinase gene 3.3 Qutob et al. ( 2006 )

AtLECRK 9.8 Qutob et al. ( 2006 )

PROPEP 21.2 Huffaker et al. ( 2006 )

HrpZ PROPEP 40.8 Huffaker et al. ( 2006 )

Chitin CEBiP 2.6 Kaku et al. ( 2006 )

NPP1 PROPEP1 26.9 Huffaker et al. ( 2006 )

CBEL WAK1 - Khatib et al. ( 2004 )

NLP pp AtLECRK 7.4 Qutob et al. ( 2006 )

WAK L7 19.5 Qutob et al. ( 2006 )