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Mitogen-activated protein kinases (MAPKs) cascades play essential roles in plants by trans-ducing developmental cues and environmental signals into cellular responses. Among the latter are microbe-associated molecular patterns perceived by pattern recognition receptors (PRRs), which trigger immunity. We found that YODA (YDA) – a MAPK kinase kinase regulating several Arabidopsis developmental processes, like stomatal patterning – also modulates immune responses. Resistance to pathogens is compromised in yda alleles, whereas plants expressing the constitutively active YDA (CA-YDA) protein show broad-spectrum resistance to fungi, bacteria, and oomycetes with different colonization modes. YDA functions in the same pathway as ERECTA (ER) Receptor-Like Kinase, regulating both immunity and stomatal patterning. ER-YDA-mediated immune responses act in parallel to canonical disease resistance pathways regulated by phytohormones and PRRs. CA-YDA plants exhibit altered cell-wall integrity and constitutively express defense-associated genes, including some encoding putative small secreted peptides and PRRs whose impairment resulted in enhanced susceptibility phenotypes. CA-YDA plants show strong reprogramming of their phosphoproteome, which contains protein targets distinct from described MAPKs substrates. Our results suggest that, in addition to stomata development, the ER-YDA pathway regulates an immune surveillance system conferring broad-spectrum disease resistance that is distinct from the canonical pathways mediated by described PRRs and defense hormones.

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.

Background: Bacillus cereus is associated with milk, dairy product, and dairy farm contamination. The aim of this study was to characterize strains of B. cereus in the small-scale artisanal cheese production chain in southwestern Mexico. Methods: 130 samples were collected. B. cereus isolation was performed on Mannitol Egg Yolk Polymyxin (MYP) agar. Genotyping, enterotoxigenic profile, and determination of genes involved in the formation of B. cereus biofilm were performed by PCR. An antimicrobial susceptibility test was made by broth microdilution assay. The phylogenetic analysis was performed by amplification and sequencing of 16s rRNA. Results: B. cereus sensu lato was isolated and molecularly identified in 16 samples and B. cereus sensu stricto (B. cereus) was the most frequently isolated and identified species (81.25%). Of all the isolated B. cereus sensu lato strains, 93.75% presented at least one gene for some diarrheagenic toxins, 87.5% formed biofilms, and 18.75% were amylolytic. All B. cereus sensu lato strains were resistant to beta-lactams and folate inhibitors. A close phylogenetic relationship between isolates was found between the cheese isolates and the air isolates. Conclusions: Strains of B. cereus sensu lato were found in small-scale artisanal cheeses on a farm in southwestern Mexico.

Background: Bacillus cereus is associated with milk, dairy product, and dairy farm contamination. The aim of this study was to characterize strains of B. cereus in the small-scale artisanal cheese production chain in southwestern Mexico. Methods: 130 samples were collected. B. cereus isolation was performed on Mannitol Egg Yolk Polymyxin (MYP) agar. Genotyping, enterotoxigenic profile, and determination of genes involved in the formation of B. cereus biofilm were performed by PCR. An antimicrobial susceptibility test was made by broth microdilution assay. The phylogenetic analysis was performed by amplification and sequencing of 16s rRNA. Results: B. cereus sensu lato was isolated and molecularly identified in 16 samples and B. cereus sensu stricto (B. cereus) was the most frequently isolated and identified species (81.25%). Of all the isolated B. cereus sensu lato strains, 93.75% presented at least one gene for some diarrheagenic toxins, 87.5% formed biofilms, and 18.75% were amylolytic. All B. cereus sensu lato strains were resistant to beta-lactams and folate inhibitors. A close phylogenetic relationship between isolates was found between the cheese isolates and the air isolates. Conclusions: Strains of B. cereus sensu lato were found in small-scale artisanal cheeses on a farm in southwestern Mexico.