Described a new plant immunity pathway in tomato that confers enhanced resistance against the bacterium Pseudomonas syringae

Mitogen-activated protein kinases (MAPK) play pivotal roles 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. The CBGP’s group of "Plant Innate immunity and resistance to necrotrophic fungi", previously demonstrated that Arabidopsis plants overexpressing a constitutively active YODA protein (AtCA-YDA) show constitutive activation of a non-canonical immune pathway and the expression of the associated defensive genes that resulted in broad-spectrum disease resistance (Sopeña-Torres et al., 2018).

In this new work led by Drs. Antonio Molina and Lucía Jordá, in collaboration with researchers from Castilla la Mancha University, Centro Nacional de Biotecnología and the companies Plant Response Biotech and Semillas Fitó, they have tested YDA function in crops immunity, by heterologous overexpressing AtCA-YDA in tomato plants (Solanum lycopersicum). We found that these AtCA-YDA plants do not show developmental phenotypes nor fitness alterations but show a reduced stomatal index and enhanced resistance to the bacterium Pseudomonas syringae pv. tomato DC3000 (Pto), and constitutively up-regulation of defense-associated genes. These results of “proof of concept” carried out in collaboration with agriculture enterprises, further confirm the function of YDA-mediated signalling pathway in crops disease resistance.

This function of YDA in tomato immunity was further supported by generating CRISPR/Cas9-edited tomato mutants impaired in the closest orthologues of AtYDA (Solyc08g081210 (SlYDA1) and Solyc03g025360 (SlYDA2)). Slyda1 and Slyda2 mutants are more susceptible to Pto in comparison to wild-type plants but only Slyda2 shows altered stomatal index. These results indicate that tomato orthologues have specialized roles and support that YDA also regulates immune responses in tomato. The results of this article suggest that SlYDA genes can be considered as genetic traits in disease resistance breeding programs of tomato and that YDA has potential biotechnological applications as it is claims in the CBGP patent of YDA gene that has been licensed to a biotech enterprise for its commercial exploitation (Molina et al., 2015. US14/652,285).