A Newly Identified Flower-Specific Splice Variant of Regulates Stamen Elongation and Endothecium Lignification in Arabidopsis.

In addition to the full-length transcript , a splice variant () of the auxin response factor gene has been reported. Here, we identified an intron-retaining variant of , , whose translated product is imported into the nucleus and has tissue-specific localization in By inducibly expressing each variant in flowers, we show that fully complements the short-stamen phenotype of the mutant and restores the expression of , encoding a key regulator of stamen elongation. By contrast, the expression of and had minor or no effects on stamen elongation and expression. Coexpression of and in both the wild type and caused premature anther dehiscence: We show that is responsible for increased expression of the jasmonic acid biosynthetic gene and that is responsible for premature endothecium lignification due to precocious expression of transcription factor gene Finally, we show that ARF8.4 binds to specific auxin-related sequences in both the and promoters and activates their transcription more efficiently than ARF8.2. Our data suggest that ARF8.4 is a tissue-specific functional splice variant that controls filament elongation and endothecium lignification by directly regulating key genes involved in these processes.