� Transcription and export (TREX) is a multi-subunit complex that links synthesis, processing
and export of mRNAs. It interacts with the RNA helicase UAP56 and export factors such as
MOS11 and ALYs to facilitate nucleocytosolic transport of mRNAs. Plant MOS11 is a conserved,
but sparsely researched RNA-binding export factor, related to yeast Tho1 and mammalian
CIP29/SARNP.
� Using biochemical approaches, the domains of Arabidopsis thaliana MOS11 required for
interaction with UAP56 and RNA-binding were identified. Further analyses revealed marked
genetic interactions between MOS11 and ALY genes. Cell fractionation in combination with
transcript profiling demonstrated that MOS11 is required for export of a subset of mRNAs
that are shorter and more GC-rich than MOS11-independent transcripts.
� The central a-helical domain of MOS11 proved essential for physical interaction with
UAP56 and for RNA-binding. MOS11 is involved in the nucleocytosolic transport of mRNAs
that are upregulated under stress conditions and accordingly mos11 mutant plants turned out
to be sensitive to elevated NaCl concentrations and heat stress.
� Collectively, our analyses identify functional interaction domains of MOS11. In addition,
the results establish that mRNA export is critically involved in the plant response to stress conditions
and that MOS11 plays a prominent role at this.