Bacterial cyclodipeptides elicit Arabidopsis thaliana immune responses reducing the pathogenic effects of Pseudomonas aeruginosa PAO1 strains on plant development.

Plants being sessile organisms are exposed to various biotic and abiotic factors, thus causing stress. The Pseudomonas aeruginosa bacterium is an opportunistic pathogen for animals, insects, and plants. Direct exposure of Arabidopsis thaliana to the P. aeruginosa PAO1 strain induces plant death by producing a wide variety of virulence factors, which are regulated mainly by quorum sensing systems. Besides virulence factors, P. aeruginosa PAO1 also produces cyclodipeptides (CDPs), which possess auxin-like activity and promote plant growth through activation of the target of the rapamycin (AtTOR) pathway. On the other hand, plant defense mechanisms are regulated through the production of phytohormones, such as salicylic acid (SA) and jasmonic acid (JA), which are induced in response to pathogen-associated molecular patterns (PAMPs), activating defense genes associated with SA and JA such as PATHOGENESIS-RELATED-1 (PR-1) and LIPOXYGENASE2 (LOX2), respectively. PR proteins are suggested to play critical roles in coordinating the Systemic Acquired Resistance (SAR). In contrast, LOX proteins (LOX2, LOX3, and LOX4) have been associated with the production of JA by producing its precursors, oxylipins. The activation of defense mechanisms involves signaling cascades such as Mitogen-Activated Protein Kinases (MAPKs) or the TOR pathway as a switch for re-directing energy towards defense or growth. In this work, we challenged A. thaliana (wild type, mpk6 or mpk3 mutants, and overexpressing TOR) seedlings with P. aeruginosa PAO1 strains to identify the role of bacterial CDPs in the plant immune response. Results showed that the pre-exposure of these Arabidopsis seedlings to CDPs significantly reduced plant infection of the pathogenic P. aeruginosa PAO1 strains, indicating that plants that over-express AtTOR or lack MPK3/MPK6 protein-kinases are more susceptible to the pathogenic effects. In addition, CDPs induced the GUS activity only in the LOX2::GUS plants, indicative of JA-signaling activation. Our findings indicate that the CDPs are molecules that trigger SA-independent and JA-dependent defense responses in A. thaliana; hence, bacterial CDPs may be considered elicitors of the Arabidopsis immune response to pathogens.

[Painful nodules on the soles in a pediatric patient: A diagnostic challenge]. / Nodulos plantares dolorosos tras ejercicio intenso en paciente pediátrica: Un reto diagnóstico.

INTRODUCTION: Idiopathic Palmoplantar Eccrine Hidradenitis (IPPH) is a rare neutrophilic derma tosis, with painful erythematous nodules of sudden onset in the plantar or palmoplantar region, in children without other underlying diseases. OBJECTIVE: To present a case that shows the main clinical and histological characteristics of this entity. CLINICAL CASE: 11-year-old girl with a 48-hours history of painful erythematous-violaceous nodules on the right foot plant associated with fever of up to 38.2 °C, with no history of interest except hyperhidrosis and intense exercising on previous days. Given the clinical suspicion of IPPH, a skin biopsy was performed, which showed inflammatory neutrophil infiltration around eccrine sweat glands and neutrophilic abscesses, confirming the diagnosis. Oral NSAIDs and rest were prescribed, with resolution of the lesions in 7 days. CONCLUSIONS: This case demonstrates the most important aspects of this entity, in many cases underdiagnosed, since it can be confused with other pathologies that occur with painful acral nodules, but have different pathogenic and therapeutic implications. To properly identify the IPPH allows preventing an unnecessary alarm, both patients and their parents, as in dermatologists and pediatricians themselves.

Nodulos plantares dolorosos tras ejercicio intenso en paciente pediátrica: un reto diagnóstico / Painful nodules on the soles in a pediatric patient: a diagnostic challenge

Resumen: Introducción: La Hidradenitis palmoplantar ecrina idiopática (HPPI) es una dermatosis neutrofílica infrecuente, que cursa con nódulos eritematosos dolorosos de comienzo brusco en regiones plantares o palmoplantares, en niños que no tienen otra enfermedad subyacente. Objetivo: Presentar un caso que ilustra las principales características clínicas e histológicas de la HPPI. Caso Clínico: Niña de 11 años evaluada por nódulos eritematovioláceos dolorosos en planta de pie derecho de 48 horas de evo lución y fiebre de hasta 38,2 °C, sin antecedentes de interés salvo hiperhidrosis y práctica intensa de ejercicio en los días previos. Ante la sospecha clínica de HPPI se realizó biopsia cutánea, que mostró infiltrado inflamatorio neutrofílico alrededor de glándulas sudoríparas ecrinas y abscesos de neutrófilos, confirmando el diagnóstico. Se indicaron antiinflamatorios no esteroidales orales y reposo, con resolución de las lesiones en 7 días. Conclusiones: Este caso demuestra los aspectos más importantes de la HPPI. Esta entidad en muchos casos es infradiagnosticada, dado que puede confundirse con otras patologías que también cursan con nódulos acrales dolorosos, pero tienen distintas implicacio nes patogénicas y terapéuticas. Identificar apropiadamente la HPPI permite evitar la alarma innece saria, tanto en pacientes y sus padres, como en los propios dermatólogos y pediatras.

Abstract: Introduction: Idiopathic Palmoplantar Eccrine Hidradenitis (IPPH) is a rare neutrophilic derma tosis, with painful erythematous nodules of sudden onset in the plantar or palmoplantar region, in children without other underlying diseases. Objective: To present a case that shows the main clinical and histological characteristics of this entity. Clinical Case: 11-year-old girl with a 48-hours history of painful erythematous-violaceous nodules on the right foot plant associated with fever of up to 38.2 °C, with no history of interest except hyperhidrosis and intense exercising on previous days. Given the clinical suspicion of IPPH, a skin biopsy was performed, which showed inflammatory neutrophil infiltration around eccrine sweat glands and neutrophilic abscesses, confirming the diagnosis. Oral NSAIDs and rest were prescribed, with resolution of the lesions in 7 days. Conclusions: This case demonstrates the most important aspects of this entity, in many cases underdiagnosed, since it can be confused with other pathologies that occur with painful acral nodules, but have different pathogenic and therapeutic implications. To properly identify the IPPH allows preventing an unnecessary alarm, both patients and their parents, as in dermatologists and pediatricians themselves.