LEFKOTHEA Regulates Nuclear and Chloroplast mRNA Splicing in Plants.

Eukaryotic organisms accomplish the removal of introns to produce mature mRNAs through splicing. Nuclear and organelle splicing mechanisms are distinctively executed by spliceosome and group II intron complex, respectively. Here, we show that LEFKOTHEA, a nuclear encoded RNA-binding protein, participates in chloroplast group II intron and nuclear pre-mRNA splicing. Transiently optimized LEFKOTHEA nuclear activity is fundamental for plant growth, whereas the loss of function abruptly arrests embryogenesis. Nucleocytoplasmic partitioning and chloroplast allocation are efficiently balanced via functional motifs in LEFKOTHEA polypeptide. In the context of nuclear-chloroplast coevolution, our results provide a strong paradigm of the convergence of RNA maturation mechanisms in the nucleus and chloroplasts to coordinately regulate gene expression and effectively control plant growth. • LEFKOTHEA, a nucleus-encoded RNA-binding protein, exists only in embryophytes • Embryo development relies on LEFKOTHEA function • LEFKOTHEA localizes to chloroplasts and nucleus • LEFKOTHEA catalyzes nuclear pre-mRNA and chloroplast group II intron splicing Daras et al. show that in higher land plants, both nuclear and chloroplast pre-mRNA splicing involve a common nuclear-encoded protein, LEFKOTHEA. Starting in the early stages of embryo development, LEFKOTHEA coordinates the expression of the nuclear and chloroplast genomes, thus regulating plant growth. [ABSTRACT FROM AUTHOR]