Plant ERD2‐like proteins function as endoplasmic reticulum luminal protein receptors and participate in programmed cell death during innate immunity

Abstract

SUMMARYThe hypersensitive response (HR), a form of programmed cell death (PCD), is a tightly regulated innate immune response in plants that is hypothesized to restrict pathogen growth and disease development. Although considerable efforts have been made to understand HR PCD, it remains unknown whether the retrograde pathway from the Golgi to the endoplasmic reticulum (ER) is involved. Here we provide direct genetic evidence that two Nicotiana benthamiana homologs, ERD2a and ERD2b, function as ER luminal protein receptors and participate in HR PCD. Virus-induced gene silencing (VIGS) of ERD2a and/or ERD2b caused escape of ER-resident proteins from the ER, and resulted in plants that were more sensitive to ER stress. Silencing of ERD2b delayed HR PCD induced by the non-host pathogens Xanthomonas oryzae pv. oryzae and Pseudomonas syringae pv. tomato DC3000. However, both silencing of ERD2a and co-silencing of ERD2a and ERD2b exacerbated HR PCD. Individual and combined suppression of ERD2a and ERD2b exaggerated R gene-mediated cell death. Nevertheless, silencing of ERD2a and/or ERD2b had no detectable effects on bacterial growth. Furthermore, VIGS of several putative ligands of ERD2a/2b, including the ER quality control (ERQC) component genes BiP, CRT3 and UGGT, had different effects on HR PCD induced by different pathogens. This indicates that immunity-related cell death pathways are separate with respect to the genetic requirements for these ERQC components. These results suggest that ERD2a and ERD2b function as ER luminal protein receptors to ensure ERQC and alleviate ER stress, thus affecting HR PCD during the plant innate immune response.

uORF-mediated translation allows engineered plant disease resistance without fitness costs

“…The TBF1 promoter was amplified from the Arabidopsis genomic DNA and flanked with Hind III/ Spe I using primers P14/P15 and ligated into pGX179, which was cut with Hind III/ Xba I, to generate pGX181 ( TBF1p:uorfs TBF1 -Gateway-NOS ). LUC , GFP ER and snc1 were amplified from pGWB235 26 , GFP-HDEL 27 and the snc1 mutant genomic DNA, respectively. TBF1-YFP and NPR1-EGFP were fused together through PCR, cloned via ligation independent cloning 25 .…”

“…Xoc strain RH3 was grown on nutrient agar medium (0.1% yeast extract, 0.3% beef extract, 0.5% polypeptone, and 1% sucrose) at 28 °C for 2 d before resuspension in sterile water and dilution to OD 600nm = 0.5 for inoculation. 5 to 10 leaves of each plant were inoculated by the penetration method using a needleless syringe at the tillering stage 27 . Disease was scored by measuring the lesion length at 14 dpi.…”

Plant ERD2s self-interact and interact with GTPase-activating proteins and ADP-ribosylation factor 1

“…We found that ERD2a (GU388433) and ERD2b (GU388432) had the activity of ER luminal protein receptor. 17 By a high-throughput virus-induced gene silencing (VIGS) screen, we found that knocking down ERD2b delayed the nonhost pathogen Xanthomonas oryzae unknown. All the results suggest a conserved role of ERD2 may exist evolutionarily.…”

“…8 In contrasts, Arabidopsis ERD2a, N. benthamiana ERD2a and ERD2b have been found to function in yeast. 10,17 Further, ERD2a and ERD2b have been proved to function as ER luminal protein receptor in plants. 17 Whether the other five class II ERD2-like proteins in plants can function as ER luminal protein receptor needs to be investigated further.…”

“…10,17 Further, ERD2a and ERD2b have been proved to function as ER luminal protein receptor in plants. 17 Whether the other five class II ERD2-like proteins in plants can function as ER luminal protein receptor needs to be investigated further. Fourth, mutation of Arabidopsis ERD2b specifically affected CRT3, but not CRT1 or CRT2 or BiP, although they all carry a C-terminal HDEL signal.…”