PLANT&FOREST

Characterization of Phytophthora capsici effector genes and their functional repertoire

Saima Arif1   Gi Taek Lim1   Sun Ha Kim1   Sang-Keun Oh1,*   

1Department of Applied Biology, College of Agriculture & Life Sciences, Chungnam National University, Daejeon 34134, Korea

Abstract

Phytophthora capsici is one of the most destructive hemibiotrophic pathogens; it can cause blight in chili peppers, and secrete various effector proteins to infect the plants. These effectors contain an N-terminal conserved RXLR motif. Here, we generated full-length RXLR effector coding genes using primer pairs, and cloned them into the pGR106 vector for in planta expression. Two of these genes, PcREK6 and PcREK41 (P. capsici RXLR effector from the Korea isolate), were further characterized. PcREK6 and PcREK41 genes showed that they encode effector proteins with a general modular structure, including the N-terminal conserved RXLR-DEER motif and signal peptide sequences. PcREK6 and PcREK41 expressions were strongly induced when the chili pepper plants (Capsicum annuum) were challenged with P. capsici. These results provide molecular evidence to elucidate the virulence or avirulence factors in chili pepper. Our results also showed that two effectors induce hypersensitive response (HR) cell death when expressed in chili leaves. Cell death suppression assays in Nicotiana benthamiana revealed that most effectors could not suppress programmed cell death (PCD) triggered by Bcl-associated X (BAX) or Phytophthora infestans elicitin (INF1). However, PcREK6 fully suppressed PCD triggered by BAX, while PcREK41 partially suppressed PCD triggered by INF1 elicitin. These results suggest that PcREK effectors from P. capsici interact with putative resistance (R) proteins in planta, and different effectors may target different pathways in a plant cell to suppress pattern-triggered immunity (PTI) or effector-triggered immunity (ETI).

Figures & Tables

Fig. 1. Reverse transcription polymerase chain reaction (RT-PCR) analysis. RXLR effectors of are expressed during infection of chili pepper. KACC isolate was inoculated on chili leaves ( cv. Jindaegeon). Infected leaves were harvested at 0, 1, 2, 3, 4 days after inoculation (dai) for total RNA extraction. RT-PCR was performed using the RXLR effectors from Korea isolate () effector specific primers of The constitutive Actin () and elongation factor 1 alpha () were used as controls.