MSH1-induced heritable enhanced growth vigor through grafting is associated with the RdDM pathway in plants (Nature Comms.)

The ability of plants to adapt to diverse environments and environmental conditions has been attributed to phenotypic plasticity mediated by genetic and epigenetic changes. Through grafting experiments, small RNA has been shown to be a mobile molecule that can be transmitted long-distance via the vascular system. While several studies have demonstrated the effect of this mobility at the recipient tissue, knowledge about effects in the graft progeny remain elusive. The nuclear-encoded MutS HOMOLOGUE 1 (MSH1) gene controls organelle genome stability, and when mutated leads to graft-transmissible epigenetic changes; wildtype plants grafted on msh1 rootstock display enhanced growth vigor and seed yield in the graft progeny. Kundariya et al. explored the relationship between this heritable enhanced vigor and epigenetic processes in tomato and arabidopsis. Transcriptomic analysis in graft progenies showed differential gene expression in stress and hormone pathways in both species, and bisulfite sequencing showed that graft progeny from msh1 rootstock undergoes methylation repatterning. To identify phenotype-related differentially methylated genes, network-based enrichment (NBE) analysis was performed. Phytohormone signaling network was enriched, with auxin as the most significant. Growth enhancement in the root in msh1 was subsequently shown to be associated with auxin transport. The observed heritable growth enhancement through grafting in msh1 was lost in the dcl2,3,4 mutant, suggesting that this phenomenon is associated with the RdDM pathway. (Summary by Toluwase Olukayode @toluxylic) Nature Comms. 10.1038/s41467-020-19140-x