Indole-3-Butyric Acid Induces Ectopic Formation of Metaxylem in the Hypocotyl of Arabidopsis thaliana without Conversion into Indole-3-Acetic Acid and with a Positive Interaction with Ethylene

• Published in: International journal of molecular sciences Vol. 18; no. 11; p. 2474
• Main Authors: Fattorini, Laura, Della Rovere, Federica, Andreini, Eleonora, Ronzan, Marilena, Falasca, Giuseppina, Altamura, Maria Maddalena
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 21.11.2017; MDPI
• Subjects: Acetic acid; Acids; adventitious root formation; Auxins; Butyric acid; Conversion; Differentiation; Ethylene; hypocotyl pericycle; hypocotyl vascular system; Hypocotyls; indole-3-acetic acid; Indole-3-butyric acid; Indoleacetic acid; metaxylem; protoxylem; Seedlings; Xylem; xylogenesis in planta; hypocotyl pericycle; protoxylem; indole-3-butyric acid; adventitious root formation; hypocotyl vascular system; metaxylem; xylogenesis in planta; ethylene; indole-3-acetic acid
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms18112474

The role of the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) and of the auxin-interacting phytohormone ethylene, on the ectopic formation of primary xylem (xylogenesis in planta) is still little known. In particular, auxin/ethylene-target tissue(s), modality of the xylary process (trans-differentiation vs. de novo formation), and the kind of ectopic elements formed (metaxylem vs. protoxylem) are currently unknown. It is also unclear whether IBA may act on the process independently of conversion into IAA. To investigate these topics, histological analyses were carried out in the hypocotyls of Arabidopsis wild type seedlings and and mutants, which are blocked in IBA-to-IAA conversion and ethylene signalling, respectively. The seedlings were grown under darkness with either IAA or IBA, combined or not with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. Adventitious root formation was also investigated because this process may compete with xylogenesis. Our results show that ectopic formation of protoxylem and metaxylem occurred as an indirect process starting from the pericycle periclinal derivatives of the hypocotyl basal part. IAA favoured protoxylem formation, whereas IBA induced ectopic metaxylem with ethylene cooperation through the EIN3EIL1 network. Ectopic metaxylem differentiation occurred independently of IBA-to-IAA conversion as mediated by ECH2 and IBR10, and in the place of IBA-induced adventitious root formation.