Functional Divergence of Two Secreted Immune Proteases of Tomato

Abstract

Rcr3 and Pip1 are paralogous secreted papain-like proteases of tomato. Both proteases are inhibited by Avr2 from the fungal pathogen Cladosporium fulvum, but only Rcr3 acts as a co-receptor for Avr2 recognition by the tomato Cf-2 immune receptor. Here, we show that Pip1-depleted tomato plants are hyper-susceptible to fungal, bacterial, and oomycete plant pathogens, demonstrating that Pip1 is an important broad-range immune protease. By contrast, in the absence of Cf-2, Rcr3 depletion does not affect fungal and bacterial infection levels but causes increased susceptibility only to the oomycete pathogen Phytophthora infestans. Rcr3 and Pip1 reside on a genetic locus that evolved over 36 million years ago. These proteins differ in surface-exposed residues outside the substrate-binding groove, and Pip1 is 5- to 10-fold more abundant than Rcr3. We propose a model in which Rcr3 and Pip1 diverged functionally upon gene duplication, possibly driven by an arms race with pathogen-derived inhibitors or by coevolution with the Cf-2 immune receptor detecting inhibitors of Rcr3, but not of Pip1.

Screen of Non-annotated Small Secreted Proteins of Pseudomonas syringae Reveals a Virulence Factor That Inhibits Tomato Immune Proteases

“…This is consistent with a role for secreted immune proteases being harmful to PtoDC3000 because transgenic tomato lines with reduced Pip1 protein and activity levels are significantly more susceptible for PtoDC3000 infection [46]. Thus, Cip1 provides protection against secreted host proteases that would otherwise suppress pathogen growth.…”

From structure to function – a family portrait of plant subtilases

“…This notion is further supported by the observation that pathogens target apoplastic SBTs in an attempt to suppress host defense. The interaction of pathogen effectors with plant proteases at the plant–pathogen interface thus constitutes evidence for the important role played by apoplastic proteases during plant–pathogen coevolution (Dong et al ., ; Ilyas et al ., ).…”

Frameshift Mutation Confers Function as Virulence Factor to Leucine-Rich Repeat Protein from Acidovorax avenae

“…PR proteins play roles in both constitutive and induced defense responses. For instance, several plants such as potato and tomato contain basal levels of proteases in their apoplasts, including serine protease–like P69 and cysteine protease–like Rcr3, which are required for tomato resistance against Cladosporium fulvum (Song et al, 2009), and Phytophthora inhibited protease 1 (Pip1), a potato resistance factor to Phytophthora infestans (Ilyas et al, 2015). In addition to their functions as constitutive defense factors, several PR-containing proteases are induced both locally and systemically after pathogen infection, suggesting that their activities directly or indirectly affect pathogen growth.…”

“…Deletion of Rcr3 increases the susceptibility of tomato to P. infestans and C. fulvum . Likewise, silencing of C14 in Nicotiana benthamiana significantly increases susceptibility to P. infestans (Ilyas et al, 2015). These data indicate that proteases play a determinative role in the execution of defenses against plant pathogens.…”