Auxin controls Arabidopsis anther dehiscence by regulating endothecium lignification and jasmonic acid biosynthesis

Authors

  • Valentina Cecchetti,

    1. Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy
    2. Istituto di Biologia e Patologia Molecolari Consiglio Nazionale delle Ricerche, Sapienza Università di Roma, Rome, Italy
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  • Maria Maddalena Altamura,

    1. Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Rome, Italy
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  • Patrizia Brunetti,

    1. Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy
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  • Valentina Petrocelli,

    1. Istituto di Biologia e Patologia Molecolari Consiglio Nazionale delle Ricerche, Sapienza Università di Roma, Rome, Italy
    Current affiliation:
    1. Istituto FIRC di Oncologia Molecolare, Milano, Italy
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  • Giuseppina Falasca,

    1. Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Rome, Italy
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  • Karin Ljung,

    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden
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  • Paolo Costantino,

    1. Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy
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  • Maura Cardarelli

    Corresponding author
    1. Istituto di Biologia e Patologia Molecolari Consiglio Nazionale delle Ricerche, Sapienza Università di Roma, Rome, Italy
    • Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy
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For correspondence (e-mail maura.cardarelli@uniroma1.it).

Summary

It has been suggested that, in Arabidopsis, auxin controls the timing of anther dehiscence, possibly by preventing premature endothecium lignification. We show here that auxin content in anthers peaks before the beginning of dehiscence and decreases when endothecium lignification occurs. We show that, in the auxin-perception mutants afb1-3 and tir1 afb2 afb3, endothecium lignification and anther dehiscence occur earlier than wild-type, and the gene encoding the transcription factor MYB26, which is required for endothecium lignification, is over-expressed specifically at early stages; in agreement, MYB26 expression is reduced in naphthalene acetic acid-treated anthers, and afb1 myb26 double mutants show no endothecial lignification, suggesting that auxin acts through MYB26. As jasmonic acid (JA) controls anther dehiscence, we analysed how auxin and JA interact. In the JA-defective opr3 mutant, indehiscent anthers show normal timing of endothecium lignification, suggesting that JA does not control this event. We show that expression of the OPR3 and DAD1 JA biosynthetic genes is enhanced in afb1-3 and tir1 afb2 afb3 flower buds, but is reduced in naphthalene acetic acid-treated flower buds, suggesting that auxin negatively regulates JA biosynthesis. The double mutant afb1 opr3 shows premature endothecium lignification, as in afb1-3, and indehiscent anthers due to lack of JA, which is required for stomium opening. By treating afb1 opr3 and opr3 inflorescences with JA, we show that a high JA content and precocious endothecium lignification both contribute to induction of early anther dehiscence. We propose that auxin controls anther dehiscence timing by negatively regulating two key events: endothecium lignification via MYB26, and stomium opening via the control of JA biosynthesis.

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