Sclareol Induces Plant Resistance to Root-Knot Nematode Partially Through Ethylene-Dependent Enhancement of Lignin Accumulation

The root-knot nematode (RKN) is one of the most devastating parasitic nematodes of plants. Although some secondary metabolites released by the host plant play roles as defense substances against parasitic nematodes, the mechanism underlying the induction of such defense responses is not fully understood. We found that sclareol, a natural diterpene known as an antimicrobial and defense-related molecule, inhibited RKN penetration of tomato and Arabidopsis roots. Sclareol induced genes related to ethylene (ET) biosynthesis and signaling and phenylpropanoid metabolism in Arabidopsis roots. In roots of ein2-1, an ET-insensitive mutant line, both sclareol-induced inhibition of RKN penetration and sclareol-induced enhancement of lignin accumulation were abolished. A mutant defective in lignin accumulation did not exhibit such inhibition. Sclareol also activated MPK3 and MPK6, Arabidopsis mitogen-activated protein kinases whose activation is required for triggering ET biosynthesis. Sclareol-induced inhibition of RKN penetration was exhibited by mutants of neither MPK3 nor MPK6. Treatment with a biosynthetic precursor of ET was insufficient compared with sclareol treatment to inhibit RKN penetration, suggesting the existence of an ET-independent signaling pathway leading to RKN resistance. These results suggested that sclareol induced resistance to RKN penetration partially through ET-dependent accumulation of lignin in roots.

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Manipulation of Plant Cells by Cyst and Root-Knot Nematode Effectors

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-12-0106-fi ◽

2013 ◽

Vol 26 (1) ◽

pp. 9-16 ◽

Cited By ~ 114

Author(s):

Tarek Hewezi ◽

Thomas J. Baum

Keyword(s):

Biological Activities ◽

Defense Responses ◽

Effector Proteins ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Root Knot Nematode ◽

Root Cells ◽

Gland Cells ◽

Esophageal Gland ◽

Plant Parasitic

A key feature of sedentary plant-parasitic nematodes is the release of effector proteins from their esophageal gland cells through their stylets into host roots. These proteinaceous stylet secretions have been shown to be crucial for successful parasitism by mediating the transition of normal root cells into specialized feeding sites and by negating plant defenses. Recent technical advances of purifying mRNA from esophageal gland cells of plant-parasitic nematodes coupled with emerging sequencing technologies is steadily expanding our knowledge of nematode effector repertoires. Host targets and biological activities of a number of nematode effectors are continuously being reported and, by now, a first picture of the complexity of sedentary nematode parasitism at the molecular level is starting to take shape. In this review, we highlight effector mechanisms that recently have been uncovered by studying the host–pathogen interaction. These mechanisms range from mediating susceptibility of host plants to the actual triggering of defense responses. In particular, we portray and discuss the mechanisms by which nematode effectors modify plant cell walls, negate host defense responses, alter auxin and polyamine signaling, mimic plant molecules, regulate stress signaling, and activate hypersensitive responses. Continuous molecular characterization of newly discovered nematode effectors will be needed to determine how these effectors orchestrate host signaling pathways and biological processes leading to successful parasitism.

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SlWRKY45 Interacts with Jasmonate-ZIM Domain Proteins to Negatively Regulate Defense Against Root Knot Nematode Meloidogyne incognita in Tomato

10.22541/au.164151237.72268573/v1 ◽

2022 ◽

Author(s):

Huang Huang ◽

Wenchao Zhao ◽

Hui Qiao ◽

Chonghua Li ◽

Xuechun Ma ◽

...

Keyword(s):

Meloidogyne Incognita ◽

Defense Responses ◽

Wrky Transcription Factor ◽

Parasitic Nematodes ◽

Allene Oxide ◽

Wild Type ◽

Root Knot Nematode ◽

Abiotic And Biotic Stresses ◽

Biotic Stresses ◽

Gall Index

Root knot nematode (RKN), a kind of plant parasitic nematodes, leads to large reduction of crop yield, and seriously damages the agricultural production. The phytohormone jasmonates (JAs) act as important signals to regulate resistance against multiple abiotic and biotic stresses. However, little is known about the mechanism of JA-mediated defense responses against RKN in tomato. In this study, we found that the WRKY transcription factor SlWRKY45 interacts with most of the Jasmonate-ZIM domain proteins (JAZs) in yeast and plant. Overexpression of SlWRKY45 decreased plant resistance to RKN Meloidogyne incognita with increased gall index. We further generated slwrky45 mutants using the CRISPR/Cas9 technology, and discovered that the gall index and the number of nematodes and females in slwrky45 mutants are significantly reduced compared with wild type, as inoculated with RKN Meloidogyne incognita. Moreover, the contents of jasmonic acid and JA-isoleucine (JA-Ile) were highly increased in slwrky45 mutants with RKN Meloidogyne incognita infection compared with wild type. Furthermore, EMSA, and Dual-LUC assays demonstrated that SlWRKY45 directly binds and represses jasmonate biosynthesis gene ALLENE OXIDE CYCLASE ( AOC). Overall, our findings reveled that JAZ-interaction protein SlWRKY45 negatively controls plant defense against RKN Meloidogyne incognita by the regulation of JA biosynthesis in tomato.

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Pathogenicity and Metabolites of Endoparasitic Nematophagous Fungus Drechmeria coniospora YMF1.01759 against Nematodes

Microorganisms ◽

10.3390/microorganisms9081735 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1735

Author(s):

Juan Wan ◽

Zebao Dai ◽

Keqin Zhang ◽

Guohong Li ◽

Peiji Zhao

Keyword(s):

Secondary Metabolites ◽

Nematophagous Fungus ◽

Parasitic Nematodes ◽

Plant Parasitic Nematodes ◽

Root Knot Nematode ◽

Active Metabolites ◽

Water Control ◽

Egg Hatching ◽

Fermentation Products ◽

Plant Parasitic

Plant parasitic nematodes cause severe damage to crops. Endoparasitic nematophagous fungi (ENF) are a type of important biocontrol fungi, which can cause disease or kill nematodes by producing various spores. As a major ENF, Drechmeria coniospora displays certain potential for controlling plant-parasitic nematodes. In this study, the pathogenicity and secondary metabolites of the endoparasitic fungus D. coniospora YMF1.01759 were investigated. The strain D. coniospora YMF1.01759 had high infection efficiency against nematodes. The process of infecting nematodes by the strain was observed under an electron microscope. Here, 13 metabolites including one new compound 4(S)-butoxy-3-(butoxymethyl)-2-hydroxycyclopent-2-en-1-one (2) were isolated and identified from the fermentation products of D. coniospora YMF1.01759 cultured in a SDAY solid medium. Furthermore, a bioassay showed that 5-hydroxymethylfuran-2-carboxylic acid (1) is toxic to the root knot nematode Meloidogyne incognita and affects the hatching of its egg. Thereby, the nematicidal mortality attained 81.50% at 100 μg/mL for 48 h. Furthermore, egg hatching was inhibited at the tested concentrations, compared with water control eggs. This is the first report on the secondary metabolites of the ENF D. coniospora. The results indicated that D. coniospora could infect nematodes by spores and produce active metabolites to kill nematodes. The biological control potential of D. coniospora against nematodes was expounded further.

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SUMO enables substrate selectivity by mitogen-activated protein kinases to regulate immunity in plants

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2021351118 ◽

2021 ◽

Vol 118 (10) ◽

pp. e2021351118

Author(s):

Vivek Verma ◽

Anjil K. Srivastava ◽

Catherine Gough ◽

Alberto Campanaro ◽

Moumita Srivastava ◽

...

Keyword(s):

Transcription Factor ◽

Protein Kinases ◽

Defense Responses ◽

Substrate Selectivity ◽

Modification System ◽

Mitogen Activated Protein Kinases ◽

Cellular Events ◽

Sumo Proteases ◽

Mitogen Activated Protein ◽

Elicitor Treatment

The versatility of mitogen-activated protein kinases (MAPKs) in translating exogenous and endogenous stimuli into appropriate cellular responses depends on its substrate specificity. In animals, several mechanisms have been proposed about how MAPKs maintain specificity to regulate distinct functional pathways. However, little is known of mechanisms that enable substrate selectivity in plant MAPKs. Small ubiquitin-like modifier (SUMO), a posttranslational modification system, plays an important role in plant development and defense by rapid reprogramming of cellular events. In this study we identified a functional SUMO interaction motif (SIM) in Arabidopsis MPK3 and MPK6 that reveals a mechanism for selective interaction of MPK3/6 with SUMO-conjugated WRKY33, during defense. We show that WRKY33 is rapidly SUMOylated in response to Botrytis cinerea infection and flg22 elicitor treatment. SUMOylation mediates WRKY33 phosphorylation by MPKs and consequent transcription factor activity. Disruption of either WRKY33 SUMO or MPK3/6 SIM sites attenuates their interaction and inactivates WRKY33-mediated defense. However, MPK3/6 SIM mutants show normal interaction with a non-SUMOylated form of another transcription factor, SPEECHLESS, unraveling a role for SUMOylation in differential substrate selectivity by MPKs. We reveal that the SUMO proteases, SUMO PROTEASE RELATED TO FERTILITY1 (SPF1) and SPF2 control WRKY33 SUMOylation and demonstrate a role for these SUMO proteases in defense. Our data reveal a mechanism by which MPK3/6 prioritize molecular pathways by differentially selecting substrates using the SUMO–SIM module during defense responses.

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