The plant pathogen Pseudomonas aeruginosa triggers a DELLA-dependent seed germination arrest in Arabidopsis

Abstract

To anticipate potential seedling damage, plants block seed germination under unfavorable conditions. Previous studies investigated how seed germination is controlled in response to abiotic stresses through gibberellic and abscisic acid signaling. However, little is known about whether seeds respond to rhizosphere bacterial pathogens. We found that Arabidopsis seed germination is blocked in the vicinity of the plant pathogen Pseudomonas aeruginosa. We identified L-2-amino-4-methoxy-trans-3-butenoic acid (AMB), released by P. aeruginosa, as a biotic compound triggering germination arrest. We provide genetic evidence that in AMB-treated seeds DELLA factors promote the accumulation of the germination repressor ABI5 in a GA-independent manner. AMB production is controlled by the quorum sensing system IQS. In vitro experiments show that the AMB-dependent germination arrest protects seedlings from damage induced by AMB. We discuss the possibility that this could serve as a protective response to avoid severe seedling damage induced by AMB and exposure to a pathogen.

The Transcription Factor INDUCER OF CBF EXPRESSION1 Interacts with ABSCISIC ACID INSENSITIVE5 and DELLA Proteins to Fine-Tune Abscisic Acid Signaling during Seed Germination in Arabidopsis

“…In the presence of GA, the GA receptors GA INSENSITIVE DWARF1 ([GID1]a, GID1b, and GID1c) and the F-box ubiquitin ligase SLEEPY1 (as an SCF SLEEPY1 complex) recruit DELLA proteins for ubiquitination and subsequent degradation (Dill et al, 2004;Ueguchi-Tanaka et al, 2005;Nakajima et al, 2006;Harberd et al, 2009;Claeys et al, 2014). RGL2 is a critical suppressor of seed germination (Lee et al, 2002;Tyler et al, 2004;Piskurewicz et al, 2008), and GAI and RGA also repress seed germination (Cao et al, 2005;Piskurewicz et al, 2009;Chahtane et al, 2018). All five DELLA genes are expressed during seed germination (Tyler et al, 2004), and GAI, RGA, and RGL2 are responsive to ABA during seed germination (Piskurewicz et al, 2008).…”

Transcriptome Profiling Analysis Reveals Co-Regulation of Hormone Pathways in Foxtail Millet during Sclerospora graminicola Infection

“…In our study, GA was abundant in foxtail millet after infection with S. graminicola, signal transduction pathways were suppressed, and the expression of the phytochrome-interacting factor TF3 was significantly reduced. Chahtane et al (2018) [25] reported that l-2-amino-4-methoxy-trans-3-butenoic acid secreted by Pseudomonas aeruginosa directly acts on…”

“…In our study, GA was abundant in foxtail millet after infection with S. graminicola, signal transduction pathways were suppressed, and the expression of the phytochrome-interacting factor TF3 was significantly reduced. Chahtane et al (2018) [25] reported that l-2-amino-4-methoxy-trans-3-butenoic acid secreted by Pseudomonas aeruginosa directly acts on DELLA proteins of the GA signal transduction pathway to inhibit seed germination in Arabidopsis thaliana, regardless of GA content. Our results suggest that S. graminicola infection might block the GA signal transduction.…”

More than words: the chemistry behind the interactions in the plant holobiont

“…Based on these findings, it is clear that seeds have developed a sentinel molecular system to ensure that germination progresses to plantlet growth in supportive biotic and abiotic environments. Notably, and in contrast to their interaction with P. fluorescens , Arabidopsis seeds block their germination in the presence of the plant pathogen Pseudomonas aeruginosa to prevent potential damage the bacterial cells could inflict on the emerging plantlet (Chahtane et al ., 2018). This response is based on detection of molecules secreted by pathogenic bacteria into the spermosphere, such as l ‐2‐amino‐4‐methoxy‐trans‐3‐butenoic acid (AMB), a member of the oxyvinylglycin family, whose biological functions remain poorly understood.…”