The THO/TREX complex mediates the transport of nascent mRNAs from the nucleus towards the cytoplasm in animals, and it has a role in small RNA-dependent processes in plants. Here we describe five mutant alleles of Arabidopsis thaliana THO2, whichencodes a core subunit of the plant THO/TREX complex. tho2 mutants present strong developmental defects resembling those in plants compromised in microRNA (miRNA) activity. In agreement, not only the levels of siRNAs, but also of mature miRNAs were reduced in tho2 mutants. As a consequence miRNA target mRNAs accumulated to higher levels than in wild type. Yeast two hybrid experiments showed that THO2 does not seem to interact with any of the known miRNA biogenesis components, implying a more indirect role of THOs in small RNA biogenesis. We also detected alterations in the splicing pattern of genes encoding Serine/Arginine-rich proteins in tho2 mutants, suggesting a previously unappreciated role of the THO/TREX complex in alternative splicing.

• Anchilie G. Francisco(School of Applied Biosciences, Kyungpook National University)
• Pablo A. Manavella(Department of Molecular Biology, Max Planck Institute for Developmental Biology)
• Hyeon Ju Eo(School of Applied Biosciences, Kyungpook National University)
• Ji Eun Jeon(School of Applied Biosciences, Kyungpook National University)
• Patricia Lang(Department of Molecular Biology, Max Planck Institute for Developmental Biology)
• Sung Aeong Oh(School of Applied Biosciences, Kyungpook National University)
• Jong-Tae Song(School of Applied Biosciences, Kyungpook National University)
• Soon Ki Park(School of Applied Biosciences, Kyungpook National University) Corresponding Author