Details

Autor(en) / Beteiligte

• Iannetta, Anthony A.
• Rogers, Holden T.
• Al‐Mohanna, Thualfeqar
• O’Brien, Juliana N.
• Wommack, Andrew J.
• Popescu, Sorina C.
• Hicks, Leslie M.

Titel

Profiling thimet oligopeptidase‐mediated proteolysis in Arabidopsis thaliana

Ist Teil von

• The Plant journal : for cell and molecular biology, 2021-04, Vol.106 (2), p.336-350

Ort / Verlag

England: Blackwell Publishing Ltd

Erscheinungsjahr

2021

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Significance Statement Arabidopsis thimet oligopeptidases (TOPs) are critical components in responses to stress, but their exact roles are not well characterized. Herein, a combination of quantitative in vivo peptidomics and in vitro validation was used to identify TOP substrates, providing a framework for TOP signaling networks and guiding future experiments in how the interplay between proteolytic pathways and defense signaling can be harnessed for the benefit of adaptation and tolerance mechanisms of crops. SUMMARY Protein homeostasis (proteostasis) is crucial for proper cellular function, including the production of peptides with biological functions through controlled proteolysis. Proteostasis has roles in maintenance of cellular functions and plant interactions with the environment under physiological conditions. Plant stress continues to reduce agricultural yields causing substantial economic losses; thus, it is critical to understand how plants perceive stress signals to elicit responses for survival. As previously shown in Arabidopsis thaliana, thimet oligopeptidases (TOPs) TOP1 (also referred to as organellar oligopeptidase) and TOP2 (also referred to as cytosolic oligopeptidase) are essential components in plant response to pathogens, but further characterization of TOPs and their peptide substrates is required to understand their contributions to stress perception and defense signaling. Herein, label‐free peptidomics via liquid chromatography‐tandem mass spectrometry was used to differentially quantify 1111 peptides, originating from 369 proteins, between the Arabidopsis Col‐0 wild type and top1top2 knock‐out mutant. This revealed 350 peptides as significantly more abundant in the mutant, representing accumulation of these potential TOP substrates. Ten direct substrates were validated using in vitro enzyme assays with recombinant TOPs and synthetic candidate peptides. These TOP substrates are derived from proteins involved in photosynthesis, glycolysis, protein folding, biogenesis, and antioxidant defense, implicating TOP involvement in processes aside from defense signaling. Sequence motif analysis revealed TOP cleavage preference for non‐polar residues in the positions surrounding the cleavage site. Identification of these substrates provides a framework for TOP signaling networks, through which the interplay between proteolytic pathways and defense signaling can be further characterized.