Pythium infection activates conserved plant defense responses in mosses.
The moss Physcomitrella patens (P. patens) is a useful model to study abiotic stress responses since it is highly tolerant to drought, salt and osmotic stress. However, very little is known about the defense mechanisms activated in this moss after pathogen assault. In this study, we show that P. patens activated multiple and similar responses against Pythium irregulare and Pythium debaryanum, including the reinforcement of the cell wall, induction of the defense genes CHS, LOX and PAL, and accumulation of the signaling molecules jasmonic acid (JA) and its precursor 12-oxo-phytodienoic acid (OPDA). However, theses responses were not sufficient and infection could not be prevented leading to hyphae colonization of moss tissues and plant decay. Pythium infection induced reactive oxygen species production and caused cell death of moss tissues. Taken together, these data indicate that Pythium infection activates in P. patens common responses to those previously characterized in flowering plants. Microscopic analysis also revealed intracellular relocation of chloroplasts in Pythium-infected tissues toward the infection site. In addition, OPDA, JA and its methyl ester methyl jasmonate induced the expression of PAL. Our results show for the first time JA and OPDA accumulation in a moss and suggest that this defense pathway is functional and has been maintained during the evolution of plants.
Oliver
Juan Pablo
JP
Departamento de Biología Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600, Montevideo, Uruguay.
Castro
Alexandra
A
Gaggero
Carina
C
Cascón
Tomas
T
Schmelz
Eric A
EA
Castresana
Carmen
C
Ponce de León
Inés
I
D044002:Bryophyta / Q000382:microbiology / Q000502:physiology*; D018744:DNA, Plant / Q000235:genetics; D010937:Plant Growth Regulators / Q000502:physiology; D011775:Pythium / Q000472:pathogenicity*
D018744:DNA, Plant; D010937:Plant Growth Regulators