The <i>Medicago truncatula</i> lncRNA <i>ENOD40</i> is a mediator of <i>microRNA169</i> -controlled <i>NF-YA</i> activity in nodule initiation
Tristan Wijsman, Nadiatul A. Mohd‐Radzman, Jieyu Liu, Giles Oldroyd, Wouter Kohlen, Olga Kulikova, Renze Heidstra, Ben Scheres, Henk Franssen
Abstract
The hallmark of the legume lncRNA EARLY NODULIN40 ( ENOD40 ), involved in rhizobium-induced nodulation, is the presence of a highly conserved stretch of 24 nucleotides, designated box2, preceded by a small open-reading-frame (sORF) coding for a peptide of 12 to 13 amino acids. Although there is a well-established link between ENOD40 and nodulation, it is not fully clear by which mechanism ENOD40 functions in this process. Here, we show that a region harboring box2 can complement nodule formation in an ENOD40 knock-out mutant ( enod40-1-2/1 ). The sequence of box2 bears the characteristics of a miR169 target mimic. We show that the artificial target mimic MIM169defg can indeed complement the reduced capability of nodule formation in enod40-1-2/1 , and that box2 exhibits target mimic activity in a transient luciferase assay. In addition, the introduction of a miR169 -resistant form of MtNF-YA1 also elevates the capacity to form nodules in enod40-1-2/1. We conclude that ENOD40 effectuates nodule initiation by posttranscriptional upregulation of the miR169 target NF-YA1 , which encodes an essential transcription factor in this step of the nodulation process.