Identification of tomato phosphatidylinositol-specific phospholipase-C (PI-PLC) family members and the role of PLC4 and PLC6 in HR and disease resistance

Abstract

SUMMARYThe perception of pathogen-derived elicitors by plants has been suggested to involve phosphatidylinositolspecific phospholipase-C (PI-PLC) signalling. Here we show that PLC isoforms are required for the hypersensitive response (HR) and disease resistance. We characterised the tomato [Solanum lycopersicum (Sl)] PLC gene family. Six Sl PLC-encoding cDNAs were isolated and their expression in response to infection with the pathogenic fungus Cladosporium fulvum was studied. We found significant regulation at the transcriptional level of the various SlPLCs, and SlPLC4 and SlPLC6 showed distinct expression patterns in C. fulvum-resistant Cf-4 tomato. We produced the encoded proteins in Escherichia coli and found that both genes encode catalytically active PI-PLCs. To test the requirement of these Sl PLCs for full Cf-4-mediated recognition of the effector Avr4, we knocked down the expression of the encoding genes by virus-induced gene silencing. Silencing of SlPLC4 impaired the Avr4/Cf-4-induced HR and resulted in increased colonisation of Cf-4 plants by C. fulvum expressing Avr4. Furthermore, expression of the gene in Nicotiana benthamiana enhanced the Avr4/Cf-4-induced HR. Silencing of SlPLC6 did not affect HR, whereas it caused increased colonisation of Cf-4 plants by the fungus. Interestingly, Sl PLC6, but not Sl PLC4, was also required for resistance to Verticillium dahliae, mediated by the transmembrane Ve1 resistance protein, and to Pseudomonas syringae, mediated by the intracellular Pto/Prf resistance protein couple. We conclude that there is a differential requirement of PLC isoforms for the plant immune response and that Sl PLC4 is specifically required for Cf-4 function, while Sl PLC6 may be a more general component of resistance protein signalling.

Defense activation triggers differential expression ofphospholipase-C(PLC) genes and elevated temperature induces phosphatidic acid (PA) accumulation in tomato

“…Phospholipid-modifying enzymes are therefore considered to be key players in successful defense of plants against intruders. [3][4][5] Several studies showed that cellular defense signaling requires phosphatidylinositol-specific phospholipase C (PI-PLC) enzyme activity. PI-PLC enzymes are considered to be signal transducers, mainly due to the signaling roles attributed to their substrates and reaction products.…”

The tomato phosphatidylinositol-phospholipase C2 (SlPLC2) is required for defense gene induction by the fungal elicitor xylanase

“…For this, we employed a set of SlPLC1 to SlPLC6 gene-specific primers previously used by Vossen et al (2010). Fig.…”

“…The expression levels of the various SlPLCs were found to be 95 differentially regulated in C. fulvum-inoculated resistant and susceptible tomato plants (Vossen et al, 2010). By performing silencing assays, it was demonstrated that SlPLC6 is required for resistance to C. fulvum, Verticillium dahliae and P. syringae, while SlPLC4 is specifically involved in the induction of a hypersensitive response (HR) triggered upon Avr4 perception by the Cf-4 100 resistance protein (Vossen et al, 2010). Based on this evidence, the authors concluded that there are different PI-PLC isoforms participating in the signalling during different pathogen perception in plant defense.…”

“…There are nine PI-PLC genes in the Arabidopsis thaliana genome (Mueller-Roeber and Pical, 2002), whereas in tomato (Solanum lycopersicum, Sl) Vossen et al (2010) characterized a PI-PLC gene family composed of six members, named SlPLC1 M a n u s c r i p t 6 to SlPLC6. The expression levels of the various SlPLCs were found to be 95 differentially regulated in C. fulvum-inoculated resistant and susceptible tomato plants (Vossen et al, 2010).…”

“…There are nine PI-PLC genes in the Arabidopsis thaliana genome (Mueller-Roeber and Pical, 2002), whereas in tomato (Solanum lycopersicum, Sl) Vossen et al (2010) characterized a PI-PLC gene family composed of six members, named SlPLC1 M a n u s c r i p t 6 to SlPLC6. The expression levels of the various SlPLCs were found to be 95 differentially regulated in C. fulvum-inoculated resistant and susceptible tomato plants (Vossen et al, 2010). By performing silencing assays, it was demonstrated that SlPLC6 is required for resistance to C. fulvum, Verticillium dahliae and P. syringae, while SlPLC4 is specifically involved in the induction of a hypersensitive response (HR) triggered upon Avr4 perception by the Cf-4 100 resistance protein (Vossen et al, 2010).…”