The plant defense and pathogen counterdefense mediated by Hevea brasiliensis serine protease HbSPA and Phytophthora palmivora extracellular protease inhibitor PpEPI10

Abstract

Rubber tree (Hevea brasiliensis Muell. Arg) is an important economic crop in Thailand. Leaf fall and black stripe diseases caused by the aggressive oomycete pathogen Phytophthora palmivora, cause deleterious damage on rubber tree growth leading to decrease of latex production. To gain insights into the molecular function of H. brasiliensis subtilisin-like serine proteases, the HbSPA, HbSPB, and HbSPC genes were transiently expressed in Nicotiana benthamiana via agroinfiltration. A functional protease encoded by HbSPA was successfully expressed in the apoplast of N. benthamiana leaves. Transient expression of HbSPA in N. benthamiana leaves enhanced resistance to P. palmivora, suggesting that HbSPA plays an important role in plant defense. P. palmivora Kazal-like extracellular protease inhibitor 10 (PpEPI10), an apoplastic effector, has been implicated in pathogenicity through the suppression of H. brasiliensis protease. Semi-quantitative RT-PCR revealed that the PpEPI10 gene was significantly up-regulated during colonization of rubber tree by P. palmivora. Concurrently, the HbSPA gene was highly expressed during infection. To investigate a possible interaction between HbSPA and PpEPI10, the recombinant PpEPI10 protein (rPpEPI10) was expressed in Escherichia coli and purified using affinity chromatography. In-gel zymogram and co-immunoprecipitation (co-IP) assays demonstrated that rPpEPI10 specifically inhibited and interacted with HbSPA. The targeting of HbSPA by PpEPI10 revealed a defense-counterdefense mechanism, which is mediated by plant protease and pathogen protease inhibitor, in H. brasiliensis-P. palmivora interactions.

Semi-quantitative RT-PCR analysis of transcripts encoding protease inhibitor inHevea brasiliensisMuell. Arg latex

“…The recent semi-quantitative RT-PCR study showed that a protease inhibitor PpEPI10 gene was significantly up regulated during colonization of rubber tree by Phytophthora palmivora which later interact with the subtilisin proteases in rubber tree. This research revealed the strength of semiquantitative RT-PCR [32]. In this study, the semi-quantitative RT-PCR on HbPI transcripts was able to confirm the relatively stable expression among five conditions in rubber tree clone PB 260.…”

Infection mechanisms and putative effector repertoire of the mosquito pathogenic oomycete Pythium guiyangense uncovered by genomic analysis

“…Another oomycete pathogen, Ph . palmivora also produced a KPI, PpEP to suppress plant defense [47]. Therefore, we speculate that the large number of KPIs secreted by P .…”

Devastating intimacy: the cell biology of plant–Phytophthora interactions

“…A degree of host specificity in the protease inhibitor suite may also occur in P. palmivora . This brutal pathogen is not deterred by the high levels of papain in papaya due to the efficiency of one of its cysteine protease inhibitors PpaEPIC8 (Gumtow et al ., 2018) whereas, for its infection of rubber trees, the Kazal‐like serine protease inhibitor PpEPI10 may be more important (Ekchaweng et al ., 2017).…”