Beschreibung:
<jats:title>SUMMARY</jats:title><jats:p>Auxin Response Factor 8 plays a key role in late stamen development: its splice variants <jats:italic>ARF8.4</jats:italic> and <jats:italic>ARF8.2</jats:italic> control stamen elongation and anther dehiscence. Here, we characterized the role of ARF8 isoforms in pollen fertility. By phenotypic and ultrastructural analysis of <jats:italic>arf8‐7</jats:italic> mutant stamens, we found defects in pollen germination and viability caused by alterations in exine structure and pollen coat deposition. Furthermore, tapetum degeneration, a prerequisite for proper pollen wall formation, is delayed in <jats:italic>arf8‐7</jats:italic> anthers. In agreement, the genes encoding the transcription factors <jats:italic>TDF1</jats:italic>, <jats:italic>AMS</jats:italic>, <jats:italic>MS188</jats:italic> and <jats:italic>MS1</jats:italic>, required for exine and pollen coat formation, and tapetum development, are downregulated in <jats:italic>arf8‐7</jats:italic> stamens. Consistently, the sporopollenin content is decreased, and the expression of sporopollenin synthesis/transport and pollen coat protein biosynthetic genes, regulated by AMS and MS188, is reduced. Inducible expression of the full‐length isoform <jats:italic>ARF8.1</jats:italic> in <jats:italic>arf8‐7</jats:italic> inflorescences complements the pollen (and tapetum) phenotype and restores the expression of the above transcription factors. Chromatin immunoprecipitation‐quantitative polymerase chain reaction assay revealed that ARF8.1 directly targets the promoters of <jats:italic>TDF1</jats:italic>, <jats:italic>AMS</jats:italic> and <jats:italic>MS188</jats:italic>. In conclusion, the <jats:italic>ARF8.1</jats:italic> isoform controls pollen and tapetum development acting directly on the expression of <jats:italic>TDF1</jats:italic>, <jats:italic>AMS</jats:italic> and <jats:italic>MS188</jats:italic>, which belong to the pollen/tapetum genetic pathway.</jats:p>