An extremely low stomatal density mutant overcomes cooling limitations at supra-optimal temperature by adjusting stomatal size and leaf thickness.

The impact of global warming on transpiration and photosynthesis would compromise plant fitness, impacting on crop yields and ecosystem functioning. In this frame, we explored the performance of a set of Arabidopsis mutants carrying partial or total loss-of-function alleles of stomatal development genes and displaying distinct stomatal abundances. Using microscopy and non-invasive imaging techniques on this genotype collection, we examined anatomical leaf and stomatal traits, plant growth and development, and physiological performance at optimal (22°C) and supra-optimal (30°C) temperatures. All genotypes showed thermomorphogenetic responses but no signs of heat stress. Data analysis singled out an extremely low stomatal abundance mutant, spch-5. At 22°C, spch-5 had lower transpiration and warmer leaves than the wild type. However, at 30°C, this mutant developed larger stomata and thinner leaves, paralleled by a notable cooling capacity, similar to that of the wild type. Despite their low stomatal density (SD), spch-5 plants grown at 30°C showed no photosynthesis or growth penalties. The behavior of spch-5 at supra-optimal temperature exemplifies how the effect of very low stomatal numbers can be counteracted by a combination of larger stomata and thinner leaves. Furthermore, it provides a novel strategy for coping with high growth temperatures.

YODA Kinase Controls a Novel Immune Pathway of Tomato Conferring Enhanced Disease Resistance to the Bacterium Pseudomonas syringae.

Mitogen-activated protein kinases (MAPK) play pivotal roles in transducing developmental cues and environmental signals into cellular responses through pathways initiated by MAPK kinase kinases (MAP3K). AtYODA is a MAP3K of Arabidopsis thaliana that controls stomatal development and non-canonical immune responses. Arabidopsis plants overexpressing a constitutively active YODA protein (AtCA-YDA) show broad-spectrum disease resistance and constitutive expression of defensive genes. We tested YDA function in crops immunity by heterologously overexpressing AtCA-YDA in Solanum lycopersicum. We found that these tomato AtCA-YDA plants do not show developmental phenotypes and fitness alterations, except a reduction in stomatal index, as reported in Arabidopsis AtCA-YDA plants. Notably, AtCA-YDA tomato plants show enhanced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and constitutive upregulation of defense-associated genes, corroborating the functionality of YDA in tomato immunity. This function was further supported by generating CRISPR/Cas9-edited tomato mutants impaired in the closest orthologs of AtYDA [Solyc08g081210 (SlYDA1) and Solyc03g025360 (SlYDA2)]. Slyda1 and Slyda2 mutants are highly susceptible to P. syringae pv. tomato DC3000 in comparison to wild-type plants but only Slyda2 shows altered stomatal index. These results indicate that tomato orthologs have specialized functions and support that YDA also regulates immune responses in tomato and may be a trait for breeding disease resistance.

Intervenciones comunitarias para la promoción de hábitos alimentarios saludables: resultados de una revisión sistemática / Community interventions to promote healthy nutritional habits: results of a systematic review

Objetivo: identificar elementos técnicos de intervenciones comunitarias en hábitos alimentarios, susceptibles de ser implementados en el contexto de ciudades latinoamericanas. Metodología: se realizó una revisión sistemática de los estudios publicados desde 1990, enfatizando en la descripción del proceso y la evaluación de la efectividad de las intervenciones. Resultados: de 25 experiencias revisadas, 23 abordaron exclusivamente intervenciones en hábitos alimentarios y 3 restantes las combinaron con actividad física. Las teorías y modelos de comportamiento utilizadas para fundamentarlas fueron: teoría de influencias sociales (7), teoría cognitiva social (6), modelo transteórico (1), la combinación de la teoría cognitiva social y el modelo transteórico (3) y otras aproximaciones teóricas (3); cinco estudios no determinaron la teoría o modelo. Conclusiones: las intervenciones que lograron obtener un mayor efecto contaban con enfoque integral, definición clara de los objetivos, caracterización adecuada del problema, y participación de la comunidad en el diseño y definición de una etapa de mantenimiento. Se destaca la importancia de validar intervenciones en el contexto de los países latinoamericanos.