SOC1 and the RNA Underworld

Earlier, I described studies of the so-called SOC1 and FUL genes of Arabidopsis, genes that when mutated in concert change the growth habit of the plant is most remarkable ways.  A report that just came up on Plant Cell Online links one of these genes with one of the mechanisms by which RNAs are turned over in the cell.  Briefly, this study reveals that SOC1 expression is subject to posttranscriptional control, and that this control is linked with a component of the machinery that mediates nonsense-mediated decay (NMD) in plants.  This finding may be of interest for a number of reasons.  One is that NMD hasn’t yet been linked with lots of regulation in plants – it occurs, and we may infer conceptual links between alternative RNA processing and NMD, but much remains to be learned.  A second is that SOC1 functioning, previously implicated in important macroevolutionary transitions in plants, may be altered by many evolutionary processes, including those that affect RNA levels through NMD.

The abstract:

SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1) is regulated by a complex transcriptional regulatory network that allows for the integration of multiple floral regulatory inputs from photoperiods, gibberellin, and FLOWERING LOCUS C. However, the posttranscriptional regulation of SOC1 has not been explored. Here, we report that EARLY FLOWERING9 (ELF9), an Arabidopsis thaliana RNA binding protein, directly targets the SOC1 transcript and reduces SOC1 mRNA levels, possibly through a nonsense-mediated mRNA decay (NMD) mechanism, which leads to the degradation of abnormal transcripts with premature translation termination codons (PTCs). The fully spliced SOC1 transcript is upregulated in elf9 mutants as well as in mutants of NMD core components. Furthermore, a partially spliced SOC1 transcript containing a PTC is upregulated more significantly than the fully spliced transcript in elf9 in an ecotype-dependent manner. A Myc-tagged ELF9 protein (MycELF9) directly binds to the partially spliced SOC1 transcript. Previously known NMD target transcripts of Arabidopsis are also upregulated in elf9 and recognized directly by MycELF9. SOC1 transcript levels are also increased by the inhibition of translational activity of the ribosome. Thus, the SOC1 transcript is one of the direct targets of ELF9, which appears to be involved in NMD-dependent mRNA quality control in Arabidopsis.

The citation (hopefully, I will remember to update it once the paper comes out in print with the updated link for the paper copy):

Hae-Ryong Song, Ju-Dong Song, Jung-Nam Cho, Richard M. Amasino, Bosl Noh,  and Yoo-Sun Noh. The RNA Binding Protein ELF9 Directly Reduces SUPPRESSOR OF OVEREXPRESSION OF CO1 Transcript Levels in Arabidopsis, Possibly via Nonsense-Mediated mRNA Decay.  Plant Cell Advance Online Publication, Published on April 17, 2009; 10.1105/tpc.108.064774

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