MARS regulates the ABA response of the marneral cluster

In Arabidopsis, the long non-coding RNA MARS modulates the epigenetic status and chromatin conformation of the marneral metabolic gene cluster in response to ABA.

Plants communicate with their environment via the emission of molecules belonging to the large class of secondary metabolites. Their synthesis is the result of a sequence of metabolic reactions catalyzed by synchronously expressed enzymes. The genes coding for these enzymes can be located within the same genomic region, forming clusters. This cluster organization facilitates their co-expression via epigenetic or chromatin organization mechanisms. In Arabidopsis, several clustered metabolite biosynthetic pathways have been identified, including for marneral, a secondary metabolite essential for plant development.

In a study published in Molecular Plant, the REGARN group from IPS2, in collaboration with the group of Federico Ariel (Instituto de Agrobiotecnología del Litor, Santa Fe, Argentina), the group of Jose Gutierrez-Marcos (University of Warwik, UK) and the Chromosome Dynamics group from IPS2 have identified within the marneral cluster MARneral Silencing (MARS), a long non-coding RNA (lncRNA) involved in the control of the expression of the genes in this cluster. lncRNAs are long RNA molecules able to regulate the activity of other genes. In the case of the lncRNA MARS, it is able to locally modify the epigenetic status of the cluster in response to a hormonal signal (abscisic acid or ABA). Moreover, it modulates the formation of a chromatin loop joining the first gene of the biosynthetic pathway and a distal enhancer sequence activated upon ABA. More generally, this work shows that a large proportion of metabolic clusters contain lncRNA that can create an additional regulatory layer for the control of metabolic gene expression within clusters.

Figure legend: The non-coding RNA MARS regulates marneral cluster gene expression by altering its epigenetic state and chromatin conformation. Upon MARS repression (lower left panel), or upon its activation upon ABA treatment (lower right panel), LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) is removed from the cluster, triggering the decondensation of the chromatin and the formation of a loop that brings an enhancer element close to the proximal promoter of the MRN1 gene.

Le 08/03/2022