Cytoplasmic U5 snRNA promotes the heterotrophic-to-autotrophic transition via selective translational activation
Nov. 04, 2026
Dr. Danmeng Zhu published a paper in Vita.
Small nuclear RNAs (snRNAs) are best known as essential components of the nuclear spliceosome, where they catalyze pre-mRNA splicing, yet their broader regulatory potential has remained unclear. Here, we show that U5 snRNA and its cognate Sm protein partners are evolutionarily co-opted to regulate cytoplasmic translation. Light promotes U5 snRNA accumulation on polysomes, enhancing translation of nuclear-encoded mRNAs for chloroplast proteins during the heterotrophic-to-autotrophic transition, largely independent of changes in mRNA abundance. U5 snRNA base-pairs with 3′UTRs of target mRNAs via the conserved Sm site; Brassicaceae-derived cytoplasmic SmD3a couples U5 snRNA–Sm protein assemblies to eEF2, the spliceosomal SNU114 homolog, to enable translational activation. Building on this mechanism, we adapted the U5 snRNA/Sm module for the non-Brassicaceae plant Nicotiana benthamiana, which lacks an SmD3a homolog, by engineering an SmD3 variant with enhanced cytoplasmic localization through artificial intelligence-assisted rational design and optimizing U5 snRNA for target mRNA base-pairing. Transient expression of this module elevated endogenous chloroplast protein levels and increased the maximum photochemical efficiency of photosystem II by over 20%. This work reveals that spliceosomal RNAs act beyond splicing to modulate translation and suggests that manipulating the U5 snRNA/Sm module could be a viable strategy for improving photosynthetic performance.
Original Link: https://www.vita-journal.com/vita/EN/10.15302/vita.2026.10.0081