Repression of transcription factors by microRNA during seed germination and postgerminaiton: Another level of molecular repression in seeds.

There are multiple layers of molecular repression during seed germination and seedling growth which are important to maintain normal developmental programs at the early stages of plant growth. Genes involved in hormone biosynthesis and deactivation which determine the dormant or germinative status of seeds are generally controlled at the transcriptional level. In contrast, regulation involving protein modification and degradation which occur at the posttranslational level seem to be more important for the removal of proteins suppressing seed germination and seedling growth. Recent work indicates that posttranscriptional repression, another level of molecular regulation, is also critical for seed germination and postgermination. This addendum highlights recent findings concerning the repression of transcription factors by microRNA (miRNA) in Arabidopsis seeds and seedlings. Characterization of the mutant expressing miR160-resistant AUXIN RESPONSE FACTOR10 suggested the possible involvement of auxin-ABA crosstalk in seed germination. The new findings are integrated into the current model of seed germination mechanisms depicting a balance between embryo growth potential and endosperm mechanical resistance.