Type 2 Nep1-Like Proteins from the Biocontrol Oomycete Pythium oligandrum Suppress Phytophthora capsici Infection in Solanaceous Plants

Abstract

As a non-pathogenic oomycete, the biocontrol agent Pythium oligandrum is able to control plant diseases through direct mycoparasite activity and boosting plant immune responses. Several P. oligandrum elicitors have been found to activate plant immunity as microbe-associated molecular patterns (MAMPs). Necrosis- and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) are a group of MAMPs widely distributed in eukaryotic and prokaryotic plant pathogens. However, little is known about their distribution and functions in P. oligandrum and its sister species Pythium periplocum. Here, we identified a total of 25 NLPs from P. oligandrum (PyolNLPs) and P. periplocum (PypeNLPs). Meanwhile, we found that PyolNLPs/PypeNLPs genes cluster in two chromosomal segments, and our analysis suggests that they expand by duplication and share a common origin totally different from that of pathogenic oomycetes. Nine PyolNLPs/PypeNLPs induced necrosis in Nicotiana benthamiana by agroinfiltration. Eight partially purified PyolNLPs/PypeNLPs were tested for their potential biocontrol activity. PyolNLP5 and PyolNLP7 showed necrosis-inducing activity in N. benthamiana via direct protein infiltration. At sufficient concentrations, they both significantly reduced disease severity and suppressed the in planta growth of Phytophthora capsici in solanaceous plants including N. benthamiana (tobacco), Solanum lycopersicum (tomato) and Capsicum annuum (pepper). Our assays suggest that the Phytophthora suppression effect of PyolNLP5 and PyolNLP7 is irrelevant to reactive oxygen species (ROS) accumulation. Instead, they induce the expression of antimicrobial plant defensin genes, and the induction depends on their conserved nlp24-like peptide pattern. This work demonstrates the biocontrol role of two P. oligandrum NLPs for solanaceous plants, which uncovers a novel approach of utilizing NLPs to develop bioactive formulae for oomycete pathogen control with no ROS-caused injury to plants.

Nep1-like Proteins from Valsa mali Differentially Regulate Pathogen Virulence and Response to Abiotic Stresses

“…As a result, none of them triggered apparent ROS bust (Supplementary Figure S8A), which is consistent with the fact that N. benthamiana lacks the RLP23 receptor for detection of nlp20 [17,18]. Most recently, two NLPs from Pythium oligandrum have been demonstrated to activate immune responses in N. benthamiana [44]. We next tested whether VmNLP recombinant proteins function similarly.…”

Dual-Transcriptomic, Microscopic, and Biocontrol Analyses of the Interaction Between the Bioeffector Pythium oligandrum and the Pythium Soft-Rot of Ginger Pathogen Pythium myriotylum

“…P. oligandrum appears to have a priming role in stimulating plant defense responses by microbe-associated molecular pattern (MAMP) production such as the elicitin-like protein oligandrin ( Benhamou et al, 2001 ). Recently, type II NLP toxin proteins from P. oligandrum were found to suppress Phytophthora capsici infection ( Yang et al, 2021 ). Expression of putative effectors was found when P. oligandrum interacted with heat-killed Phytophthora infestans mycelia ( Horner et al, 2012 ), and these could potentially antagonize the host or mediate plant defense responses.…”

Characterization of Salivary Secreted Proteins That Induce Cell Death From Riptortus pedestris (Fabricius) and Their Roles in Insect-Plant Interactions

“…Cell death was evaluated by measuring the amount of ion leakage in leaves ( Ai et al, 2021 ; Yang et al, 2021 ). Five 9 mm-leaf disks were washed three times with distilled water and then soaked in 5 mL of distilled water for 3 h at room temperature.…”