Campus Units

Biochemistry, Biophysics and Molecular Biology, Roy J. Carver Department of, Genetics, Development and Cell Biology

Document Type


Publication Version

Accepted Manuscript

Publication Date


Journal or Book Title

Journal of Experimental Botany




The Arabidopsis thaliana T2 family endoribonuclease RNS2 localizes to the vacuole and functions in rRNA degradation. Loss of RNS2 activity impairs rRNA turnover and leads to constitutive autophagy, a process for degradation of cellular components. Autophagy is normally activated during environmental stress and is important for stress tolerance and homeostasis. Here we show that restoration of cytosolic purine nucleotide levels rescues the constitutive autophagy phenotype of rns2-2 seedlings, whereas inhibition of purine synthesis induces autophagy in wild-type seedlings. rns2-2 seedlings have reduced activity of the target of rapamycin (TOR) kinase complex, a negative regulator of autophagy, and this phenotype is rescued by addition of inosine to increase purine levels. Activation of TOR in rns2-2 by exogenous auxin blocks the enhanced autophagy, indicating a possible involvement of the TOR signaling pathway in the activation of autophagy in the rns2-2 mutant. Our data suggest a model in which loss of rRNA degradation in rns2-2 leads to a reduction in cytoplasmic nucleotide concentrations, which in turn inhibits TOR activity, leading to activation of autophagy to restore homeostasis.


This is a manuscript of an article published as Kazibwe, Zakayo, Junmarie Soto-Burgos, Gustavo C. MacIntosh, and Diane C. Bassham. "TOR mediates the autophagy response to altered nucleotide homeostasis in a ribonuclease mutant." Journal of Experimental Botany (2020). doi: 10.1093/jxb/eraa410. Posted with permission.

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The Authors



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Available for download on Thursday, September 09, 2021

Published Version