The NUP107-160 complex members NUP96/MOS3 and NUP160 are required for defence gene expression in Arabidopsis

Nuclear pore complexes (NPCs) are composed of nucleoporin proteins (NUPs) and are embedded in the double membrane of the nuclear envelope (NE). Arabidopsis NUP96/MOS3 and NUP160 are members of the evolutionary conserved NUP107-160 nuclear pore sub-complex and required for basal resistance and TIR-type NLR protein mediated immunity. Previous data indicated that both NUPs are also involved in the regulation of gene expression. A genome-wide transcriptome analysis was conducted on unchallenged mos3 and nup160 mutant plants using an RNAseq approach to identify new components of MOS3/NUP96- and NUP160-dependent defence responses. This transcriptome analysis revealed mild but significant transcriptional changes of 471 genes that are differentially expressed in both nucleoporin mutants, including the key defence regulator ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and its signalling partner PHYTOALEXIN DEFICIENT4 (PAD4) as well as the pattern recognition receptor EF-Tu RECEPTOR (EFR). Notably, only the expression of a certain set of defence-related genes was affected in mos3 and nup160 plants, suggesting that MOS3 and NUP160 are involved in regulating the expression of specific target genes. The phenotypical consequences of reduced EFR transcript abundance in mos3 and nup160 were investigated in more detail and revealed that both mutants display elevated Agrobacterium-mediated transient transformation efficiency, which is consistent with the function of EFR in restricting plant transformation by Agrobacterium. Reduced EFR gene expression, which is also reflected in reduced EFR protein abundance and impaired EFR-dependent elf18-triggered reactive oxygen species (ROS) production is likely to cause the enhanced transformation events in both mutants. The two genes whose expression was most strongly decreased in the transcriptomes of both mos3 and nup160 mutants are the predicted pumillo family (PUF) RNA binding protein PUM9 (AT1G35730) and the predicted methyl esterase MES18 (AT5G58310), whose functions have not been previously addressed in plant immunity. Using a reverse genetic approach, this study shows that MES18 but not PUM9 is required for basal resistance to the hemi-biotrophic pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. Heterologous expression of MES18 and its subsequent purification and functional characterization showed that MES18 possesses esterase activity towards the methylated, biologically inactive transport forms of the plant hormones indole-3-acetic acid (MeIAA) and jasmonic acid (MeJA). The MES18-mediated hydrolysis of MeIAA to IAA and/or MeJA to JA may therefore be involved in regulating basal resistance to Pst DC3000.2022-10-0

A rice Serine/Threonine receptor-like kinase regulates arbuscular mycorrhizal symbiosis at the peri-arbuscular membrane

In terrestrial ecosystems most plant species live in mutualistic symbioses with nutrient-delivering arbuscular mycorrhizal (AM) fungi. Establishment of AM symbioses includes transient, intracellular formation of fungal feeding structures, the arbuscules. A plant-derived peri-arbuscular membrane (PAM) surrounds the arbuscules, mediating reciprocal nutrient exchange. Signaling at the PAM must be well coordinated to achieve this dynamic cellular intimacy. Here, we identify the PAM-specific Arbuscular Receptor-like Kinase 1 (ARK1) from maize and rice to condition sustained AM symbiosis. Mutation of rice ARK1 causes a significant reduction in vesicles, the fungal storage structures, and a concomitant reduction in overall root colonization by the AM fungus Rhizophagus irregularis. Arbuscules, although less frequent in the ark1 mutant, are morphologically normal. Co-cultivation with wild-type plants restores vesicle and spore formation, suggesting ARK1 function is required for the completion of the fungal life-cycle, thereby defining a functional stage, post arbuscule development

A rice Serine/Threonine receptor-like kinase regulates arbuscular mycorrhizal symbiosis at the peri-arbuscular membrane.

In terrestrial ecosystems most plant species live in mutualistic symbioses with nutrient-delivering arbuscular mycorrhizal (AM) fungi. Establishment of AM symbioses includes transient, intracellular formation of fungal feeding structures, the arbuscules. A plant-derived peri-arbuscular membrane (PAM) surrounds the arbuscules, mediating reciprocal nutrient exchange. Signaling at the PAM must be well coordinated to achieve this dynamic cellular intimacy. Here, we identify the PAM-specific Arbuscular Receptor-like Kinase 1 (ARK1) from maize and rice to condition sustained AM symbiosis. Mutation of rice ARK1 causes a significant reduction in vesicles, the fungal storage structures, and a concomitant reduction in overall root colonization by the AM fungus Rhizophagus irregularis. Arbuscules, although less frequent in the ark1 mutant, are morphologically normal. Co-cultivation with wild-type plants restores vesicle and spore formation, suggesting ARK1 function is required for the completion of the fungal life-cycle, thereby defining a functional stage, post arbuscule development.Marie Curie FP7-PEOPLE-2013-IEF Grant number 629887 Gatsby Charitable Foundation RG60824 Isaac Newton Trust RG7410