Silencing the conserved small nuclear ribonucleoprotein SmD1 target gene alters susceptibility to root-knot nematodes in plants

Root-knot nematodes (RKNs) are among the most damaging pests of agricultural crops. Meloidogyne is an extremely polyphagous genus of nematodes that can infect thousands of plant species. A few genes for resistance (R-genes) to RKN suitable for use in crop breeding have been identified, but virulent strains and species of RKN have emerged that render these R-genes ineffective. Secretion of RKN effectors targeting plant functions mediates the reprogramming of root cells into specialized feeding cells, the giant cells, essential for RKN development and reproduction. Conserved targets among plant species define the more relevant strategies for controlling nematode infection. The EFFECTOR18 (EFF18) protein from M. incognita interacts with the spliceosomal small nuclear ribonucleoprotein D1 (SmD1) in Arabidopsis (Arabidopsis thaliana), disrupting its function in alternative splicing regulation and modulating the giant cell transcriptome. We show here that EFF18 is a conserved RKN-specific effector that targets this conserved spliceosomal SmD1 protein in Solanaceae. This interaction modulates alternative splicing events produced by tomato (Solanum lycopersicum) in response to M. incognita infection. The alteration of SmD1 expression by virus-induced gene silencing in Solanaceae affects giant cell formation and nematode development. Thus, our work defines a promising conserved SmD1 target gene to develop broad resistance for the control of Meloidogyne spp. in plants.

The root-knot nematode effector MiEFF18 interacts with the plant core spliceosomal protein SmD1 required for giant cell formation

The root-knot nematode Meloidogyne incognita secretes specific effectors (MiEFF) and induces the redifferentiation of plant root cells into enlarged multinucleate feeding 'giant cells' essential for nematode development. Immunolocalizations revealed the presence of the MiEFF18 protein in the salivary glands of M. incognita juveniles. In planta, MiEFF18 localizes to the nuclei of giant cells demonstrating its secretion during plant-nematode interactions. A yeast two-hybrid approach identified the nuclear ribonucleoprotein SmD1 as a MiEFF18 partner in tomato and Arabidopsis. SmD1 is an essential component of the spliceosome, a complex involved in pre-mRNA splicing and alternative splicing. RNA-seq analyses of Arabidopsis roots ectopically expressing MiEFF18 or partially impaired in SmD1 function (smd1b mutant) revealed the contribution of the effector and its target to alternative splicing and proteome diversity. The comparison with Arabidopsis galls data showed that MiEFF18 modifies the expression of genes important for giant cell ontogenesis, indicating that MiEFF18 modulates SmD1 functions to facilitate giant cell formation. Finally, Arabidopsis smd1b mutants exhibited less susceptibility to M. incognita infection, and the giant cells formed on these mutants displayed developmental defects, suggesting that SmD1 plays an important role in the formation of giant cells and is required for successful nematode infection.

Stability and compatibility of tacrolimus and fluconazole in 0.9% sodium chloride

OBJECTIVE

To determine the physical compatibility and chemical stability of tacrolimus injection and fluconazole injection combined in a range of concentrations used clinically for intravenous Y-site co-administration over 3 hours.

DESIGN

Tacrolimus injection (Prograf) was combined with fluconazole injection (Diflucan) in volumetric glass flasks at room temperature (23 degrees C to 25 degrees C) to form final concentrations of 5 or 20 micrograms/mL and 500 or 1,500 micrograms/mL, respectively. Immediately after preparation and at 1.5 and 3 hours, triplicate samples and controls were visually inspected and assayed in duplicate by high-performance liquid chromatography; pH of the samples was also determined.

SETTING

University of Michigan College of Pharmacy.

PATIENTS

Not applicable.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Initial and subsequent concentrations of tacrolimus and fluconazole at 1.5 and 3 hours.

RESULTS

More than 99% of the initial concentration of each drug remained in all samples throughout the study period. There was no color change, and the pH of the samples did not change appreciably.

CONCLUSION

Tacrolimus and fluconazole are stable and compatible in a range of clinically used concentrations for 3 hours and can be intravenously co-administered through a Y-site.