On August 24, 2023, Science published online a research paper titled "Functional diversification of a wild potato immune receptor at its center of origin" by the joint team of Vivianne G. A. A. Vleeshouwers of Wageningen University in the Netherlands and Thorsten Nürnberger of the University of Tübingen in Germany and their collaborators. This study successfully identified the immune receptor Pep-13 receptor unit (PERU) of potato Phytophthora infestans, which can recognize the immunogenic small peptide Pep-13 and thereby induce an immune response in potato plants. Furthermore, PERU is diverse in different species, revealing the evolution of pattern recognition receptors (PRRs). These results advance our understanding of the immune mechanisms of P. infestans and pave the way for improving potato crop resistance to this disease.
The synergistic effect of PRRs and their intracellular immune receptors can provide plants with immunity against microbial infection. The coordinated activation of plant immunity by these two spatially separated types of plant immune receptors suggests their coevolution. At the same time, the number of genes encoding cell surface and intracellular immune receptors is strongly correlated across the plant lineage, supporting that immune responses initiated in different plant cell compartments can mutually enhance each other. However, the evolution and diversity of plant PRRs remain poorly understood.
Phytophthora infestans is a pathogen of potato crops and was responsible for the Great Famine in Ireland in the mid-1800s. Its cell wall glycoprotein (GP42) can produce a conserved microbial immunogenic small peptide Pep-13, which consists of 13 amino acids and has transglutaminase (TG) activity. Using Pep-13 or Pep-25 (structural derivatives of Pep-13), this study successfully isolated the cell surface receptor PERU in potatoes that can sense Pep-13. Analysis showed that PERU is a leucine-rich repeat receptor kinase (LRR-RK), a PRR that binds Pep-13 and enhances potato immunity to P. infestans infection, and peru mutants block Pep-13-induced cell death, ROS burst, and ethylene production.
This study confirmed that Pep-13 can directly bind to the extracellular domain of PERU in vitro, but the W231A mutant of Pep-13 cannot bind to PERU. Next, the study found that Pep-13 can induce the formation of PERU-SERK3A complex. Using VIGS, this study confirmed that silencing of SERK3A significantly reduced Pep-13-induced cell death and ROS burst; however, silencing of SOBIR1 did not affect this process. In addition, overexpression of PERU can enhance potato resistance to P. infestans, while peru mutants are more susceptible to P. infestans.
By analyzing 476 genotypes from 97 wild potato species and 1 cultivated species, the study found that 350 of these genotypes (74%) did not respond to Pep-25 with cell death, indicating that most wild Solanum genotypes lack the active PERU allele. Further studies revealed that wild Solanum species encode PRRs with different ligand specificities, such as PERUDM and PERULPH.
Finally, this study shows that the plant immunity of PERU-specific binding ligands can be traced to wild tuber Solanum populations in the central Andes. In addition, PERU alleles in several potato varieties used for crop production today are similar to PERUDM.
In summary, this study successfully identified the PRR, PERU of P. infestans, which can recognize the immunogenic small peptide Pep-13. When PERU binds to Pep-13, it induces immune responses in potato plants, such as cell death, ROS burst, and ethylene production. At the same time, this study found that different alleles of PERU in potato relatives have different sensitivities to pathogenic small peptides. These insights into the immune mechanisms of P. infestans pave the way for improving potato crop resistance to this disease.
Reference:
Torres Ascurra, Y.C., et al. Functional diversification of a wild potato immune receptor at its center of origin. Science. 2023, 381(6660): 891-897.
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