Arabidopsis DXO1 affects the processing of precursors of cytoplasmic and chloroplast ribosomal RNA

Abstract

Decapping 5'-3' exoribonucleases from the DXO/Rai1 family, are highly conserved among eukaryotes and exhibit diverse enzymatic activities depending on the organism. The biochemical and structural properties of the plant DXO1 differ from the yeast and animal counterparts, which is reflected in the in vivo functions of this enzyme. Here we show that Arabidopsis DXO1 contributes to the efficient processing of rRNA precursors in both nucleolar/cytosol and chloroplast maturation pathways. However, processing defects in DXO1-deficient plants do not depend on the catalytic activity of the enzyme but rely on its plant-specific N-terminal extension. Our RNA sequencing analyses show that the dxo1 mutation deregulates the expression of many ribosomal protein genes, most likely leading to inefficient or delayed pre-rRNA maturation. Strikingly, some of the observed molecular and morphological phenotypes of dxo1 plants are suppressed by the knock-down of XRN3, providing evidence for functional interaction between DXO1 and XRN proteins.