The Phytotoxin Myrigalone A Triggers a Phased Detoxification Programme and Inhibits Lepidium sativum Seed Germination via Multiple Mechanisms including Interference with Auxin Homeostasis

  • Int J Mol Sci. 2022 Apr 21;23(9):4618. doi: 10.3390/ijms23094618.
Kazumi Nakabayashi  1 ,  Matthew Walker  1 ,  Dianne Irwin  2 ,  Jonathan Cohn  3 ,  Stephanie M Guida-English  4 ,  Lucio Garcia  3 ,  Iva Pavlović  5 ,  Ondřej Novák  5 ,  Danuše Tarkowská  5 ,  Miroslav Strnad  5 ,  Marta Pérez  1 ,  Anne Seville  2 ,  David Stock  2 ,  Gerhard Leubner-Metzger  1  5
Affiliations
  • 1. Department of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK.
  • 2. Syngenta Jealott's Hill International Research Centre, Bracknell RG42 6EY, UK.
  • 3. Syngenta Crop Protection, LLC, Research Triangle Park, NC 27709, USA.
  • 4. National Center for Genome Resources, 2935 Rodeo Park Dr E, Santa Fe, NM 87505, USA.
  • 5. Laboratory of Growth Regulators, Institute of Experimental Botany, Czech Academy of Sciences and Faculty of Science, Palacký University Olomouc, CZ-78371 Olomouc, Czech Republic.
PMID: 35563008 DOI: 10.3390/ijms23094618
Abstract

Molecular responses of Plants to natural phytotoxins comprise more general and compound-specific mechanisms. How phytotoxic Chalcones and Other Flavonoids inhibit seedling growth was widely studied, but how they interfere with seed germination is largely unknown. The dihydrochalcone and putative allelochemical myrigalone A (MyA) inhibits seed germination and seedling growth. Transcriptome (RNAseq) and hormone analyses of Lepidium sativum seed responses to MyA were compared to Other bioactive and inactive compounds. MyA treatment of imbibed seeds triggered the phased induction of a detoxification programme, altered gibberellin, cis-(+)-12-oxophytodienoic acid and jasmonate metabolism, and affected the expression of hormone transporter genes. The MyA-mediated inhibition involved interference with the antioxidant system, oxidative signalling, aquaporins and water uptake, but not uncoupling of Oxidative Phosphorylation or p-hydroxyphenylpyruvate dioxygenase expression/activity. MyA specifically affected the expression of auxin-related signalling genes, and various transporter genes, including for Auxin transport (PIN7, ABCG37, ABCG4, WAT1). Responses to auxin-specific inhibitors further supported the conclusion that MyA interferes with Auxin homeostasis during seed germination. Comparative analysis of MyA and Other phytotoxins revealed differences in the specific regulatory mechanisms and Auxin transporter genes targeted to interfere with Auxin homestasis. We conclude that MyA exerts its phytotoxic activity by multiple auxin-dependent and independent molecular mechanisms.

Keywords
ATP-binding cassette (ABC) transporter; PIN auxin efflux carrier; WRKY transcription factors; allelochemical and allelopathy; aquaporin-mediated water transport; auxin transport and homeostasis; cis-(+)-12-oxophytodienoic acid (OPDA) reductase; gibberellin metabolism; phytotoxin detoxification programme; seed germination.
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