The Arabidopsis N-terminal Acetyltransferase NAA50 Regulates Plant Growth and Defense

Stress signaling in plants is carefully regulated to ensure proper development and reproductive fitness. Overactive defense signaling can result in dwarfism as well as developmental defects. In addition to requiring a significant amount of energy, plant stress responses place a burden upon the cellular machinery, which can result in the accumulation of misfolded proteins and endoplasmic reticulum (ER) stress. Negative regulators of stress signaling, such as EDR1, ensure that stress responses are properly suspended when they are not needed. Here, we describe the role of an uncharacterized N-terminal acetyltransferase, NAA50, in the regulation of plant development and stress responses. Our results demonstrate that NAA50, an interactor of EDR1, plays an important role in regulating the tradeoff between plant growth and defense. Plants lacking NAA50 display severe developmental defects as well as induced stress responses. Reduction of NAA50 expression results in arrested stem and root growth and senescence. Furthermore, our results demonstrate that EDR1 and NAA50 are required for suppression of ER stress signaling. This work establishes that NAA50 is essential for plant development and the suppression of stress responses, likely through the regulation of ER stress. These experiments demonstrate a role for N-terminal acetylation in the suppression of ER stress, as well as the tradeoff between stress responses and development. One Sentence SummaryKnockout in Arabidopsis of the broadly conserved N-terminal acetyl transferase NAA50 induces ER stress, leading to severe dwarfism and induction of defense responses.