We have studied for many years what happens to the clipped signal peptides in organelles. These studies resulted in identification of oligopeptidases (presequence protease PreP and organellar oligopeptidase OOP), which in combination with aminopeptidases form a proteolytic network for a stepwise degradation of peptides to amino acids in plant mitochondria and chloroplasts, says Elzbieta Glaser, professor at the Department of Biochemistry and Biophysics, Stockholm University.

 

In the present work, two senior researchers in my research group, Beata Kmiec and Pedro Teixeira discovered that the lack of PreP and OOP oligopeptidases results in the accumulation of free peptides in organelles. mRNA-seq anlysis (performed by  Australian collaborators) and deep coverage proteomics, (performed at SciLife lab, KI) allowing for the identification of 17 000 transcripts and 11 000 proteins, respectively, in knockout plants uncovered a peptide‐stress response resulting in the activation of the classical plant defense pathways, however,  in the absence of a pathogen. That imposed a strong growth penalty and a reduction of the plants reproductive fitness.

 

Our results indicate that the accumulated organellar peptides are perceived as pathogenic effectors activating the signaling pathways of plant‐defense response. It will be of great interest to identify the exact signal transduction pathway for this process, says Elzbieta Glaser.

 

Front cover of The Plant Journal, vol 96, no 4, November 2018: Photo of a Arabidopsis thaliana triple oligopeptidase knockout plant (prep1prep2oop) from Kmiec et al. (pp. 705-715).

 

RESEARCH HIGHLIGHT written by S. McCormick (Research Highlights Editor)

https://www.ncbi.nlm.nih.gov/pubmed/30422378

 

ARTICLE

Accumulation of endogenous peptides triggers a pathogen stress response in Arabidopsis thaliana. Kmiec B, Branca RMM, Berkowitz O, Li L, Wang Y, Murcha MW, Whelan J, Lehtiö J, Glaser E, Teixeira PF. 2018. Plant J, 96, 705-715.

https://www.ncbi.nlm.nih.gov/pubmed/30242930

 

For further information

Elzbieta Glaser, professor at the Department of Biochemistry and Biophysics, Stockholm University

Phone: +46 8 162457

Email: e_glaser@dbb.su.se