Analysis of iron acquisition systems and their evolution in bryophytes
Date Issued
2016
Date
2016
Author(s)
Lo, Jing-Chi
Abstract
To acquire appropriate Fe, flowering plants have developed two unique strategies, the reduction-based Strategy I of non-graminaceous plants for Fe2+ and the chelation-based Strategy II of graminaceous plants for Fe3+. However, the mechanism of Fe uptake in bryophytes, the earliest diverging branch of land plants and dominant in gametophyte generation is less clear. Fe isotope fractionation analysis demonstrated that the liverwort Marchantia polymorpha and moss Physcomitrella patens use reduction-based and chelation-based Fe acquisition, respectively. In M. polymorpha, enhanced activities of ferric chelate reductase and proton ATPase were detected under Fe-deficient conditions. However, M. polymorpha did not show mugineic acid family phytosiderophores, the key components of Strategy II, or the precursor nicotianamine. Five ZIP (ZRT/IRT-like protein) homologs were identified and speculated to be involved in Fe uptake in M. polymorpha. MpZIP3 knockdown conferred reduced growth under Fe-deficient conditions, and MpZIP3 overexpression increased Fe content under excess Fe. Thus, a nonvascular liverwort, M. polymorpha, uses Strategy I for Fe acquisition. Interestingly, Fe uptake related genes involved in both reduction- and chelation- based strategies were identified in the moss Physcomitrella patens transcriptome database. Although the relative abundance of nicotianamine was increased under Fe deficiency, none of known phytosiderophores were found in the moss. NA plays important roles of Fe/Zn chelation and transport in plants. It implied that P. paten might use NA directly for Fe chelation. These findings also suggested that the reduction system was acquired in the green lineage, and unique strategy for Fe uptake was developed in P. paten. This system may have been acquired in the common ancestor of land plants and co-opted from the gametophyte to sporophyte generation in the evolution of land plants.
Subjects
Fe acquisition
reduction-based strategy
chelation-based strategy
ZIP
nicotianamine
bryophyte
Marchantia polymorpha
liverwort
Physcomitrella patens
moss
Type
thesis
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