The Role of CLE Peptides in the Suppression of Mycorrhizal Colonization of Tomato.

Symbioses with beneficial microbes are widespread in plants, but these relationships must balance the energy invested by the plants with the nutrients acquired. Symbiosis with arbuscular mycorrhizal (AM) fungi occurs throughout land plants, but our understanding of the genes and signals that regulate colonization levels is limited, especially in non-legumes. Here, we demonstrate that in tomato, two CLV3/EMBRYO-SURROUNDING REGION (CLE) peptides, SlCLE10 and SlCLE11, act to suppress AM colonization of roots. Mutant studies and overexpression via hairy transformation indicate that SlCLE11 acts locally in the root to limit AM colonization. Indeed, SlCLE11 expression is strongly induced in AM-colonized roots, but SlCLE11 is not required for phosphate suppression of AM colonization. SlCLE11 requires the FIN gene that encodes an enzyme required for CLE peptide arabinosylation to suppress mycorrhizal colonization. However, SlCLE11 suppression of AM does not require two CLE receptors with roles in regulating AM colonization, SlFAB (CLAVATA1 ortholog) or SlCLV2. Indeed, multiple parallel pathways appear to suppress mycorrhizal colonization in tomato, as double mutant studies indicate that SlCLV2 and FIN have an additive influence on mycorrhizal colonization. SlCLE10 appears to play a more minor or redundant role, as cle10 mutants did not influence intraradical AM colonization. However, the fact that cle10 mutants had an elevated number of hyphopodia and that ectopic overexpression of SlCLE10 did suppress mycorrhizal colonization suggests that SlCLE10 may also play a role in suppressing AM colonization. Our findings show that CLE peptides regulate AM colonization in tomato and at least SlCLE11 likely requires arabinosylation for activity.

Microtubule cytoskeleton and mycorrhizal roots.

For the establishment of the Arbuscular Mycorrhiza (AM) symbiosis it is essential that epidermis and cortical cells from plant roots suffer a strong reorganization to allow the penetration of intracellular fungal hyphae. In the same manner, the new formation of a periarbuscular membrane and a symbiotic interface with specific compositions are required for a functional symbiosis. It is believed that the cytoskeleton of the plant host plays an essential role in these processes, particularly the microtubule (MT) cytoskeleton, as huge modifications have been observed in the MT array of root cells accompanying the establishment of the AM symbiosis. Recent research has established a link between microtubule rearrangements and arbuscule functioning. However, further research is required to elucidate the specific functions of MT cytoskeleton along the different stages of the arbuscule life cycle and to unravel the signals triggering these changes.

DLK2 regulates arbuscule hyphal branching during arbuscular mycorrhizal symbiosis.

D14 and KAI2 receptors enable plants to distinguish between strigolactones (SLs) and karrikins (KARs), respectively, in order to trigger appropriate environmental and developmental responses. Both receptors are related to the regulation of arbuscular mycorrhiza (AM) formation and are members of the RsbQ-like family of α,ß-hydrolases. DLK2 proteins, whose function remains unknown, constitute a third clade from the RsbQ-like protein family. We investigated whether the tomato SlDLK2 is a new regulatory component in the AM symbiosis. Genetic approaches were conducted to analyze SlDLK2 expression and to understand SlDLK2 function in AM symbiosis. We show that SlDLK2 expression in roots is AM-dependent and is associated with cells containing arbuscules. SlDLK2 ectopic expression arrests arbuscule branching and downregulates AM-responsive genes, even in the absence of symbiosis; while the opposite effect was observed upon SlDLK2 silencing. Moreover, SlDLK2 overexpression in Medicago truncatula roots showed the same altered phenotype observed in tomato roots. Interestingly, SlDLK2 interacts with DELLA, a protein that regulates arbuscule formation/degradation in AM roots. We propose that SlDLK2 is a new component of the complex plant-mediated mechanism regulating the life cycle of arbuscules in AM symbiosis.

Histochemical Staining and Quantification of Arbuscular Mycorrhizal Fungal Colonization.

Histochemical staining and light microscopy-based techniques have been widely used to detect and quantify arbuscular mycorrhizal fungi (AMF) in roots. Here we describe a standardized method for staining of AMF in colonized roots, and we provide possible modifications to adjust the protocol according to particular requirements, such as the type of root material or the reduction of toxic products. In addition, we also summarize some of the most common ways to quantify arbuscular mycorrhizal colonization.

Validación de la versión en español de la Columbia-Suicide Severity Rating Scale (Escala Columbia para Evaluar el Riesgo de Suicidio) / Validation of a Spanish version of the Columbia-Suicide Severity Rating Scale (C-SSRS)

Objetivo. Examinar las propiedades psicométricas de la versión en español de la escala C-SSRS (Sp-CSSRS). Método. Estudio de validación naturalista, transversal y multicéntrico. Muestra: 467 pacientes psiquiátricos ambulatorios (242 con tentativa de suicidio previa). Instrumentos: C-SSRS; Escala de Hamilton para la Depresión (HDRS); Escala de Intencionalidad Suicida de Beck; Escala de Gravedad Médica de la Tentativa (MDS). Resultados. Validez del constructo: el coeficiente de Pearson entre la subescala de gravedad (C-Grave) y la de intensidad (C-Int) de la Sp-C-SSRS fue 0,44 (p < 0,000). El coeficiente de Pearson entre C-Grave y el ítem 3 de la HDRS fue 0,56 (p < 0,000). Para la submuestra de pacientes con tentativa de suicidio previa, se encontró una correlación estadísticamente significativa entre C-Grave y la Escala de Intencionalidad Suicida de Beck (r = 0,22; p = 0,001). Validez discriminante: se encontraron diferencias estadísticamente significativas entre las puntuaciones de C-Grave y de C-Int entre pacientes con tentativa de suicidio y sin ella (p < 0,000). La puntuación de la C-Grave clasificó adecuadamente a los pacientes en función de su puntuación en el ítem 3 de la HDRS (p < 0,009). Sensibilidad al cambio: la regresión lineal mostró que la disminución de una unidad en el ítem 3 de la HDRS se correspondió con la disminución de 5,08 unidades en la C-Grave (p = 0,141). El cambio de una unidad en el ítem 3 de la HDRS se correspondió con un cambio de 13,51 unidades en la C-Int (p = 0,007). El alfa de Cronbach fue 0,53. El análisis factorial de la C-Int identificó 2 componentes que explicaron el 55,66% de la varianza total. Conclusión. La Sp-C-SSRS es un instrumento fiable y válido para evaluar la ideación y la conducta suicidas en la práctica clínica y en contextos de investigación (AU)

Objective. To examine the psychometric properties of a Spanish version of the C-SSRS (Sp-CSSRS). Method. Data are from a naturalistic, cross-sectional, multicentre, validation study, including 467 psychiatric outpatients, 242 of whom had a history of suicide attempt. The study measures were: C-SSRS; the Hamilton Depression Rating Scale (HDRS); the Beck Suicide Intent Scale; the Medical Damage Scale. Results. Construct validity: Pearson coefficient between the C-SSRS severity (C-Sev) and intensity (C-Int) of ideation subscale scores was 0.44 (P < .000) for the total sample. Likewise, Pearson coefficient between C-Sev score and HDRS item 3 was 0.56 (P < .000). For the sub-sample of patients with suicide attempt, significant Pearson correlations were found between the C-Sev and the Beck Suicide Intent Scale scores (r = 0.22; P = .001). Discriminant validity: Significant differences were found in C-Sev and C-Int scores between patients with and without suicide attempt (P < .000). The C-Sev score discriminated between patients based on HDRS item 3 (P < .009). Sensitivity to change: Linear regression showed that a one-unit decrease in HDRS item 3 corresponded to a decrease of 5.08 units in the C-Sev score (P = .141). A one-unit change in HDRS item 3 corresponded to a change of 13.51 on the C-Int assessments (P = .007). Cronbach's alpha was 0.53 for C-Int. The principal component analysis identified 2 components that explain 55.66% of the total variance (C-Int). Conclusion. The data support that the Sp-C-SSRS is a reliable and valid instrument for assessing suicidal ideation and behaviour in daily clinical practice and research settings (AU)

Validation of a Spanish version of the Columbia-Suicide Severity Rating Scale (C-SSRS). / Validación de la versión en español de la Columbia-Suicide Severity Rating Scale (Escala Columbia para Evaluar el Riesgo de Suicidio).

OBJECTIVE: To examine the psychometric properties of a Spanish version of the C-SSRS (Sp-CSSRS). METHOD: Data are from a naturalistic, cross-sectional, multicentre, validation study, including 467 psychiatric outpatients, 242 of whom had a history of suicide attempt. The study measures were: C-SSRS; the Hamilton Depression Rating Scale (HDRS); the Beck Suicide Intent Scale; the Medical Damage Scale. RESULTS: Construct validity: Pearson coefficient between the C-SSRS severity (C-Sev) and intensity (C-Int) of ideation subscale scores was 0.44 (P<.000) for the total sample. Likewise, Pearson coefficient between C-Sev score and HDRS item 3 was 0.56 (P<.000). For the sub-sample of patients with suicide attempt, significant Pearson correlations were found between the C-Sev and the Beck Suicide Intent Scale scores (r=0.22; P=.001). Discriminant validity: Significant differences were found in C-Sev and C-Int scores between patients with and without suicide attempt (P<.000). The C-Sev score discriminated between patients based on HDRS item 3 (P<.009). Sensitivity to change: Linear regression showed that a one-unit decrease in HDRS item 3 corresponded to a decrease of 5.08 units in the C-Sev score (P=.141). A one-unit change in HDRS item 3 corresponded to a change of 13.51 on the C-Int assessments (P=.007). Cronbach's alpha was 0.53 for C-Int. The principal component analysis identified 2 components that explain 55.66% of the total variance (C-Int). CONCLUSION: The data support that the Sp-C-SSRS is a reliable and valid instrument for assessing suicidal ideation and behaviour in daily clinical practice and research settings.

Suppression of allene oxide synthase 3 in potato increases degree of arbuscular mycorrhizal fungal colonization.

Arbuscular mycorrhizal (AM) is a mutually beneficial interaction among higher plants and soil fungi of the phylum Glomeromycota. Numerous studies have pointed that jasmonic acid plays an important role in the development of the intraradical fungus. This compound belongs to a group of biologically active compounds known as oxylipins which are derived from the oxidative metabolism of polyunsaturated fatty acids. Studies of the regulatory role played by oxylipins in AM colonization have generally focused on jasmonates, while few studies exist on the 9-LOX pathway of oxylipins during AM formation. Here, the cDNA of Allene oxide synthase 3 (AOS3), a key enzyme in the 9-LOX pathway, was used in the RNA interference (RNAi) system to transform potato plants in order to suppress its expression. Results show increases in AOS3 gene expression and 9-LOX products in roots of wild type potato mycorrhizal plants. The suppression of AOS3 gene expression increases the percentage of root with mycorrhizal colonization at early stages of AM formation. AOS3 RNA interference lead to an induction of LOXA and 13-LOX genes, a reduction in AOS3 derived 9-LOX oxylipin compounds and an increase in jasmonic acid content, suggesting compensation between 9 and 13-LOX pathways. The results in a whole support the hypothesis of a regulatory role for the 9-LOX oxylipin pathway during mycorrhization.