Function and evolution of a Lotus japonicus AP2/ERF family transcription factor that is required for development of infection threads

Koji Yano, Seishiro Aoki, Meng Liu, Yosuke Umehara, Norio Suganuma, Wataru Iwasaki, Shusei Sato, Takashi Soyano, Hiroshi Kouchi, Masayoshi Kawaguchi

    Research output: Contribution to journalArticlepeer-review

    19 Citations (Scopus)

    Abstract

    Legume-rhizobium symbiosis is achieved by two major events evolutionarily acquired: root hair infection and organogenesis. Infection thread (IT) development is a distinct element for rhizobial infection. Through ITs, rhizobia are efficiently transported from infection foci on root hairs to dividing meristematic cortical cells. To unveil this process, we performed genetic screening using Lotus japonicus MG-20 and isolated symbiotic mutant lines affecting nodulation, root hair morphology, and IT development. Map-based cloning identified an AP2/ERF transcription factor gene orthologous to Medicago truncatula ERN1. LjERN1 was activated in response to rhizobial infection and depended on CYCLOPS and NSP2. Legumes conserve an ERN1 homolog, ERN2, that functions redundantly with ERN1 in M. truncatula. Phylogenetic analysis showed that the lineages of ERN1 and ERN2 genes originated from a gene duplication event in the common ancestor of legume plants. However, genomic analysis suggested the lack of ERN2 gene in the L. japonicus genome, consistent with Ljern1 mutants exhibited a root hair phenotype that is observed in ern1/ern2 double mutants in M. truncatula. Molecular evolutionary analysis suggested that the nonsynonymous/synonymous rate ratios of legume ERN1 genes was almost identical to that of non-legume plants, whereas the ERN2 genes experienced a relaxed selective constraint.

    Original languageEnglish
    Pages (from-to)193-203
    Number of pages11
    JournalDNA Research
    Volume24
    Issue number2
    DOIs
    Publication statusPublished - 2017 Apr 1

    Keywords

    • ERN1
    • Lotus japonicus
    • infection thread development
    • molecular evolutionary analysis

    ASJC Scopus subject areas

    • Molecular Biology
    • Genetics

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