Molecular machinery of auxin synthesis,secretion, and perception in the unicellular chlorophyte alga Chlorella sorokiniana UTEX 1230

Authors

Maya Khasin, University of Nebraska–LincolnFollow
Rebecca E. Cahoon, University of Nebraska-LincolnFollow
Kenneth Nickerson, University of Nebraska–LincolnFollow
Wayne R. Riekhof, University of Nebraska–LincolnFollow

ORCID IDs

http://orcid.org/0000-0002-1550-600X

http://orcid.org/0000-0003-3392-5766

http://orcid.org/0000-0002-3281-8099

Date of this Version

12-10-2018

Citation

PLOS ONE | https://doi.org/10.1371/journal.pone.0205227 December 10, 2018 1 / 13

Comments

Khasin M, Cahoon RR, Nickerson KW, Riekhof WR (2018) Molecular machinery of auxin synthesis, secretion, and perception in the unicellular chlorophyte alga Chlorella sorokiniana UTEX 1230. PLoS ONE 13(12): e0205227. https:// doi.org/10.1371/journal.pone.0205227

Abstract

Indole-3-acetic acid is a ubiquitous small molecule found in all domains of life. It is the predominant and most active auxin in seed plants, where it coordinates a variety of complex growth and development processes. The potential origin of auxin signaling in algae remains a matter of some controversy. In order to clarify the evolutionary context of algal auxin signaling, we undertook a genomic survey to assess whether auxin acts as a signaling molecule in the emerging model chlorophyte Chlorella sorokiniana UTEX 1230. C. sorokiniana produces the auxin indole-3-acetic acid (IAA), which was present in both the cell pellet and in the supernatant at a concentration of ~ 1 nM, and its genome encodes orthologs of genes related to auxin synthesis, transport, and signaling in higher plants. Candidate orthologs for the canonical AUX/IAA signaling pathway were not found; however, auxin-binding protein 1 (ABP1), an alternate auxin receptor, is present and highly conserved at essential auxin binding and zinc coordinating residues. Additionally, candidate orthologs for PIN proteins, responsible for intercellular, vectorial auxin transport in higher plants, were not found, but PILs (PIN-Like) proteins, a recently discovered family that mediates intracellular auxin transport, were identified. The distribution of auxin related gene in this unicellular chlorophyte demonstrates that a core suite of auxin signaling components was present early in the evolution of plants. Understanding the simplified auxin signaling pathways in chlorophytes will aid in understanding phytohormone signaling and crosstalk in seed plants, and in understanding the diversification and integration of developmental signals during the evolution of multicellular plants.