Project Leader Max Planck Institute of Molecular Plant Physiology
Apart from small sugars, peptides and hormones, also large proteins and RNAs are allocated via the vasculature to distant tissues. This includes all major classes of endogenous RNAs such as small si/miRNAs, transfer RNAs, and full-length protein encoding messenger RNAs (mRNAs). Recent advances in the analysis of the mobile transcriptomes from grafted Arabidopsis plants indicate that hundreds of mRNA transcripts move along the plant axis in both directions from shoot to root and from root to shoot. Single cell and tissue wide transcriptomes revealed that a surprisingly high number of mRNAs are delivered to distinct cell types and tissues such as flowers, leaves and/or roots. Our data indicate that that transported mRNAs are translated in recipient cells and that their transport does not depend on expression levels or stability. Rather a selective mRNA transport mechanism seems to be employed involving RNA-binding proteins, distinct RNA motifs and secondary m5C base modifications. In line, the mobile mRNA transcriptome changes depending on developmental stages and growth conditions and, as shown with some graft-mobile mRNAs, is required for normal growth. More recently, we have shown that Cas9 / gRNA mRNA root-to-shoot transport can be mediated by a tRNA-like sequence (TLS) motif(s). Such mobile Cas9-TLS / gRNA-TLS fusion transcripts move to grafted wild-type scions which form transgene free edited seeds in one generation.