Plant intracellular nucleotide-binding domain, leucine-rich repeat-containing receptors (NLRs) activate a robust immune response upon detection of pathogen effectors. How NLRs induce downstream immune defense genes remains poorly understood. The Mediator complex plays a central role in transducing signals from gene-specific transcription factors to the transcription machinery for gene transcription/activation. In this study, we demonstrate that MED10b and MED7 of the Mediator complex mediate jasmonate-dependent transcription repression, and coiled-coil NLRs (CNLs) in Solanaceae modulate MED10b/MED7 to activate immunity. Using the tomato CNL Sw-5b , which confers resistance to tospovirus , as a model, we found that the CC domain of Sw-5b directly interacts with MED10b. Knockout/down of MED10b and other subunits including MED7 of the middle module of Mediator activates plant defense against tospovirus . MED10b was found to directly interact with MED7, and MED7 directly interacts with JAZ proteins, which function as transcriptional repressors of jasmonic acid (JA) signaling. MED10b–MED7–JAZ together can strongly repress the expression of JA-responsive genes. The activated Sw-5b CC interferes with the interaction between MED10b and MED7, leading to the activation of JA-dependent defense signaling against tospovirus . Furthermore, we found that CC domains of various other CNLs including helper NLR NRCs from Solanaceae modulate MED10b/MED7 to activate defense against different pathogens. Together, our findings reveal that MED10b/MED7 serve as a previously unknown repressor of jasmonate-dependent transcription repression and are modulated by diverse CNLs in Solanaceae to activate the JA-specific defense pathways.

Plant‐parasitic nematodes need to deliver effectors that suppress host immunity for successful parasitism. We have characterized a novel isochorismatase effector from the root‐knot nematode Meloidogyne incognita , named Mi‐ISC‐1. The Mi‐isc‐1 gene is expressed in the subventral oesophageal glands and is up‐regulated in parasitic‐stage juveniles. Tobacco rattle virus‐induced gene silencing targeting Mi‐isc‐1 attenuated M. incognita parasitism. Enzyme activity assays confirmed that Mi‐ISC‐1 can catalyse hydrolysis of isochorismate into 2,3‐dihydro‐2,3‐dihydroxybenzoate in vitro. Although Mi‐ISC‐1 lacks a classical signal peptide for secretion at its N‐terminus, a yeast invertase secretion assay showed that this protein can be secreted from eukaryotic cells. However, the subcellular localization and plasmolysis assay revealed that the unconventional secretory signal present on the Mi‐ISC‐1 is not recognized by the plant secretory pathway and that the effector was localized within the cytoplasm of plant cells, but not apoplast, when transiently expressed in Nicotiana benthamiana leaves by agroinfiltration. Ectopic expression of Mi‐ISC‐1 in N . benthamiana reduced expression of the PR1 gene and levels of salicylic acid (SA), and promoted infection by Phytophthora capsici . The cytoplasmic localization of Mi‐ISC‐1 is required for its function. Moreover, Mi‐ISC‐1 suppresses the production of SA following the reconstitution of the de novo SA biosynthesis via the isochorismate pathway in the cytoplasm of N. benthamiana leaves. These results demonstrate that M. incognita deploys a functional isochorismatase that suppresses SA‐mediated plant defences by disrupting the isochorismate synthase pathway for SA biosynthesis to promote parasitism.

Aphelenchoides stellatusn. sp. is described and figured. The new species was isolated from packaging wood from Japan imported to Ningbo harbour, China. The new species has a body length of 485-533 μm (males) and 547-699 μm (females). The cuticle is weakly annulated and there are four lines in the lateral field. The stylet is 9-11 μm long and has small basal swellings. The excretory pore is located posterior to the nerve ring. Spicules smoothly curved, rose-thorn shaped. Apex and rostrum round, only slightly offset, dorsal limb 19-21 μm long. Male tail bearing six (2 + 2 + 2) caudal papillae. The female spermatheca is axial and oblong with round sperm present in multiple rows. Both male and female tail pegs have 3-4 processes, appearing star-like under SEM. The new species belongs to the Group 3 category ofAphelenchoidesspecies. Phylogenetic analyses based on full length ITS and 28S D2/D3 region of rDNA confirmed its morphological status as a new species.