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Title: Physcomitrella patens activates reinforcement of the cell wall, programmed cell death and accumulation of evolutionary conserved defense signals...upon Botrytis cinerea infection

item PONCE DE LEON, INES - University Of Montevideo
item Schmelz, Eric
item GAGGERO, CARINA - University Of Montevideo
item CASTRO, ALEXANDRA - University Of Montevideo
item ALVAREZ, ALFONSO - University Of Montevideo
item MONTESANO, MARCOS - University Of Montevideo

Submitted to: Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2012
Publication Date: 8/1/2012
Citation: Ponce De Leon, I., Schmelz, E.A., Gaggero, C., Castro, A., Alvarez, A., Montesano, M. 2012. Physcomitrella patens activates reinforcement of the cell wall, programmed cell death and accumulation of evolutionary conserved defense signals...upon Botrytis cinerea infection. Molecular Plant Pathology. DOI: 10.1111/J.1364-3703.2012.00806.X.

Interpretive Summary: Following attack by fungal pathogens, plants share numerous defensive biochemical responses in effort to reduce losses from disease. The evolutionarily primitive moss, Physcomitrella patens, represents an ideal model organism to explore basal processes that are likely to be conserved in crop plants and also define which traits represent more recent advances. Working with the Instituto de Investigaciones Biológicas Clemente Estable (Department of Molecular Biology, Uruguay) scientists at the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, have discovered that Physcomitrella exhibits a number of defense signaling similarities to vascular plants when attacked by the necrotrophic fungus Botrytis cinerea. Shared responses include the increased production of reactive oxygen species, and defense gene transcripts including lipoxygenase, allene oxide synthase, and phenylalanine ammonia lyase. Fatty acids such as free linolenic acid and the associated defensive phytohormone precursor 12-oxo-phytodienoic acid (OPDA) were likewise significantly elevated within 24 hours after infection. Despite increases in OPDA, no increases in the wound hormone jasmonic acid could be found yet application of methyl jasmonate reduced moss colony growth in a dose dependant manner suggesting a conserved ability to perceive jasmonates. Thus Physcomitrella can provide important evolutionary insights into the signaling and perception pathways responsible for inducible plant defenses.

Technical Abstract: The moss Physcomitrella patens is an evolutionarily basal model system suitable to analyze plant defense responses activated after pathogen assault. Upon infection with the necrotroph Botrytis cinerea (B. cinerea), several defense mechanisms are induced in P. patens, including the fortification of the plant cell wall by the incorporation of phenolic compounds and the induced expression of related genes. B. cinerea infection also activated the accumulation of reactive oxygen species and cell death with hallmarks of programmed cell death in moss tissues. Salicylic acid (SA) levels also increased after fungal infection and treatment with SA enhanced transcript accumulation of the defense gene PAL in P. patens colonies. Expression levels of genes involved in 12-oxo- phytodienoic acid (OPDA) synthesis, including LOX and AOS, increased in P. patens gametophytes after pathogen assault, correlated with a rise in free linolenic acid and OPDA concentrations. However, jasmonic acid (JA) could not be detected in healthy or infected tissues of this plant. Our results suggest that although conserved defense signals like SA and OPDA are synthesized and likely involved in the defense response of P. patens against B. cinerea infection, JA production appears to be missing. Interestingly, P. patens responded to OPDA and methyl jasmonate by reducing moss colony growth and rhizoid length, suggesting that jasmonate perception is present in mosses. Thus, P. patens can provide clues to the evolution of different defense pathways in plants, including signalling and perception of OPDA and jasmonates in non-flowering and flowering plants.