NatB-Mediated N-Terminal Acetylation Affects Growth and Biotic Stress Responses

• Published in: Plant physiology (Bethesda) 2020-02, Vol.182 (2), p.792-806
• Main Authors: Huber, Monika, Bienvenut, Willy V, Linster, Eric, Stephan, Iwona, Armbruster, Laura, Sticht, Carsten, Layer, Dominik, Lapouge, Karine, Meinnel, Thierry, Sinning, Irmgard, Giglione, Carmela, Hell, Ruediger, Wirtz, Markus
• Format: Article
• Language: English
• Subjects: Acetylation; Acetyltransferases - genetics; Acetyltransferases - metabolism; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Catalytic Domain - genetics; Computational Biology; Gene Expression Profiling; Gene Ontology; In Vitro Techniques; Life Sciences; Mutagenesis, Insertional; N-Terminal Acetyltransferase B - genetics; N-Terminal Acetyltransferase B - metabolism; Osmotic Pressure; Proteome - genetics; Proteome - metabolism; Seedlings - enzymology; Seedlings - genetics; Seedlings - growth & development; Seedlings - metabolism; Stress, Physiological - genetics; Stress, Physiological - radiation effects
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.19.00792

N -terminal acetylation (NTA) is one of the most abundant protein modifications in eukaryotes. In humans, NTA is catalyzed by seven N -acetyltransferases (NatA-F and NatH). Remarkably, the plant Nat machinery and its biological relevance remain poorly understood, although NTA has gained recognition as a key regulator of crucial processes such as protein turnover, protein-protein interaction, and protein targeting. In this study, we combined in vitro assays, reverse genetics, quantitative -terminomics, transcriptomics, and physiological assays to characterize the Arabidopsis ( ) NatB complex. We show that the plant NatB catalytic (NAA20) and auxiliary subunit (NAA25) form a stable heterodimeric complex that accepts canonical NatB-type substrates in vitro. In planta, NatB complex formation was essential for enzymatic activity. Depletion of NatB subunits to 30% of the wild-type level in three Arabidopsis T-DNA insertion mutants ( , , and ) caused a 50% decrease in plant growth. A complementation approach revealed functional conservation between plant and human catalytic NatB subunits, whereas yeast NAA20 failed to complement Quantitative N-terminomics of approximately 1000 peptides identified 32 bona fide substrates of the plant NatB complex. In vivo, NatB was seen to preferentially acetylate N termini starting with the initiator Met followed by acidic amino acids and contributed 20% of the acetylation marks in the detected plant proteome. Global transcriptome and proteome analyses of NatB-depleted mutants suggested a function of NatB in multiple stress responses. Indeed, loss of NatB function, but not NatA, increased plant sensitivity toward osmotic and high-salt stress, indicating that NatB is required for tolerance of these abiotic stressors.