Loss of a Conserved tRNA Anticodon Modification Perturbs Plant Immunity

Abstract

tRNA is the most highly modified class of RNA species, and modifications are found in tRNAs from all organisms that have been examined. Despite their vastly different chemical structures and their presence in different tRNAs, occurring in different locations in tRNA, the biosynthetic pathways of the majority of tRNA modifications include a methylation step(s). Recent discoveries have revealed unprecedented complexity in the modification patterns of tRNA, their regulation and function, suggesting that each modified nucleoside in tRNA may have its own specific function. However, in plants, our knowledge on the role of individual tRNA modifications and how they are regulated is very limited. In a genetic screen designed to identify factors regulating disease resistance and activation of defenses in Arabidopsis, we identified SUPPRESSOR OF CSB3 9 (SCS9). Our results reveal SCS9 encodes a tRNA methyltransferase that mediates the 2´-O-ribose methylation of selected tRNA species in the anticodon loop. These SCS9-mediated tRNA modifications enhance during the course of infection with the bacterial pathogen Pseudomonas syringae DC3000, and lack of such tRNA modification, as observed in scs9 mutants, severely compromise plant immunity against the same pathogen without affecting the salicylic acid (SA) signaling pathway which regulates plant immune responses. Our results support a model that gives importance to the control of certain tRNA modifications for mounting an effective immune response in Arabidopsis, and therefore expands the repertoire of molecular components essential for an efficient disease resistance response.

Deciphering the epitranscriptome: A green perspective

“…When comparing different plant tissues, differences in the abundance and types of tRNA modifications were found when comparing different plant tissues and cell cultures (Jones and Scott ; Hienzsch et al ) and new and old leaves (Shugart ). Recently, the tRNA modification 2’‐0‐cytosine methylation (Cm) was shown to be increased in response to pathogen infection in Arabidopsis (Ramirez et al ). In other organisms, several tRNA modifications were shown to be induced under stress conditions such as oxidative stress (Chan et al ; Chan et al ), nutrient starvation (Preston et al ) and toxins (Hertz et al ).…”

“…Identification of RNA modifications present in tRNAs is only half the story − the tRNA modifying enzymes, or ‘writers’ are just beginning to be characterized in plants. A combination of bioinformatics and reverse genetics approaches have been used to predict and identify tRNA modifying enzymes in Arabidopsis (Golovko et al ; Chen et al ; Miyawaki et al ; Pavlopoulou and Kossida ; Zhou et al ; Chen et al ; Hu et al ; Mehlgarten et al ; Leihne et al ; Zhou et al ; Burgess et al ; Ramirez et al ). Transfer RNA modifying enzymes have been characterized for mediating base methylations of guanine and cytosine residues, and modifying 2′‐O‐ribose methylations.…”

“…Another tRNA methylation modification is 2′‐O‐ribose methylation. Recently, an Arabidopsis homolog of yeast TRM7 (At5g01230), a 2′‐O‐ribose methyltransferase, was identified to be required for efficient immune response to Pseudomonas syringae (Ramirez et al ).…”

The Arabidopsis TRM61/TRM6 complex is a bona fide tRNA N1-methyladenosine methyltransferase

“…TRM4B (At2g22400) acts as a tRNA 5-methylcytosine (m 5 C) methyltransferase and is required for root development ( Burgess et al , 2015 ; David et al , 2017 ). AtTRM7 (At5g01230), a 2´-O-ribose methyltransferase, is functional in the efficient immune response to Pseudomonas syringae ( Ramirez et al ., 2015 ). AtTAD2 (At1g48175) and AtTAD3 (At5g24670) catalyse adenosine-to-inosine editing at position 34 of several cytosolic (cyt) tRNA species, and knockout of either gene leads to arrested embryo development at the globular stage ( Zhou et al , 2014 ).…”

Retraction: Loss of a Conserved tRNA Anticodon Modification Perturbs Plant Immunity

“…The authors of this article [ 1 ], with the support of the Instituto de Biología Molecular y Celular de Plantas, are retracting this publication for the following reasons.…”