The mRNA export pathway in plants

A double lipid bilayer separating the nucleus from the cytoplasm, termed the nuclear envelope, is a defining feature of eukaryotes. Nucleocytoplasmic transport of macromolecules through the nuclear pores enables fine-tuned regulation of biologic processes. All mature mRNAs are delivered to the cytoplasm from the nucleus via an mRNA export pathway. Much work has been done in yeast and animals to study the machinery of mRNA export. However, until recently, research on plant mRNA export has been quite limited. Genetic, bioinformatic, and biochemical investigations have expanded our understanding of the mRNA export process in plants. Here, we review recent progress that has been made elucidating the components of the mRNA export pathway in plants. MOS3 (MODIFIER OF SNC1, 3) /AtNup96 and AtNup160 are both components of the highly conserved Nup107–160 nucleoporin complex and were shown to play key roles in mRNA export. MOS11 (MODIFIER OF SNC1, 11), which is homologous to the RNA helicase enhancer CIP29 in human, was recently found to be involved in the same pathway as MOS3. A DEAD Box RNA helicase, LOS4 (low expression of osmotically responsive genes 4) was also found to play a role in the mRNA export process, putatively by carrying mRNA molecules through the nuclear envelope. Recently, a protein complex homologous to the yeast TREX-2 complex was also found to play important roles in mRNA export in plants. It appears that most players in the mRNA export pathway are highly conserved among plants, yeast and animals.