Abstract
Plants have developed complex defense mechanisms to cope with microbial pathogens. Pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) are perceived by pattern recognition receptors (PRRs), leading to the activation of defense. While substantial progress has been made in understanding the activation of plant defense by PAMPs and DAMPs recognition in tracheophytes, far less information exists on related processes in early divergent plants like mosses. The aim of this study was to identify genes that were induced in P. patens in response to elicitors of Pectobacterium carotovorum subsp. carotovorum, using a cDNA suppression subtractive hybridization (SSH) method. A total of 239 unigenes were identified, including genes involved in defense responses related to the shikimate, phenylpropanoid, and oxylipin pathways. The expression levels of selected genes related to these pathways were analyzed using quantitative RT-PCR, confirming their rapid induction by P.c. carotovorum derived elicitors. In addition, P. patens induced cell wall reinforcement after elicitor treatment by incorporation of phenolic compounds, callose deposition, and elevated expression of Dirigent-like encoding genes. Small molecule defense markers and phytohormones such as cinnamic acid, 12-oxo-phytodienoic acid, and auxin levels all increased in elicitor-treated moss tissues. In contrast, salicylic acid levels decreased while abscisic acid levels remained unchanged. P. patens reporter lines harboring an auxin-inducible promoter fused to β-glucuronidase revealed GUS activity in protonemal and gametophores tissues treated with elicitors of P.c. carotovorum, consistent with a localized activation of auxin signaling. These results indicate that P. patens activates the shikimate, phenylpropanoid, oxylipins, and auxin pathways upon treatment with P.c. carotovorum derived elicitors.
Highlights
Plants employ complex defense mechanisms against microbial infection that involves recognition of the invader, activation of signal transduction pathways, and the production of proteins and metabolites with different roles in defense
In P. patens, moss tissues treated with culture filtrate (CF) of P.c. carotovorum develop disease symptoms after 24 h, evidenced by browning of cell walls in protonemal tissues and basal cauloid and rhizoids of gametophore tissues, which correlates with an increase of dead cells (Figure 1)
In order to identify more genes involved in the defense response of P. patens to P.c. carotovorum derived elicitors, we generated a suppression subtractive hybridization (SSH) cDNA library
Summary
Plants employ complex defense mechanisms against microbial infection that involves recognition of the invader, activation of signal transduction pathways, and the production of proteins and metabolites with different roles in defense. Some PRRs recognize host-derived “danger” signals, which are endogenous elicitors (damage-associated molecular patterns; DAMPs) such as plant cell wall and cutin fragments that are released by the enzymatic action of pathogens or wounding (Lotze et al, 2007; Boller and Felix, 2009). Cellular responses of flowering plants to PAMPs and DAMPs include the accumulation of reactive oxygen species (ROS), the reinforcement of plant cell walls through deposition of callose and lignin, the synthesis of hormones, the expression of defense genes and the production of defensive proteins and metabolites (Hückelhoven, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
