LAX and SPA: Major regulators of shoot branching in rice

Keishi Komatsu, Masahiko Maekawa, Shin Ujiie, Yuzuki Satake, Ikuyo Furutani, Hironobu Okamoto, Ko Shimamoto, Junko Kyozuka

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    282 Citations (Scopus)


    The aerial architecture of plants is determined primarily by the pattern of shoot branching. Although shoot apical meristem initiation during embryogenesis has been extensively studied by molecular genetic approaches using Arabidopsis, little is known about the genetic mechanisms controlling axillary meristem initiation, mainly because of the insufficient number of mutants that specifically alter it. We identified the LAX PANICLE (LAX) and SMALL PANICLE (SPA) genes as the main regulators of axillary meristem formation in rice. LAX encodes a basic helix-loop-helix transcription factor and is expressed in the boundary between the shoot apical meristem and the region of new meristem formation. This pattern of LAX expression was repeatedly observed in every axillary meristem, consistent with our observation that LAX is involved in the formation of all types of axillary meristems throughout the ontogeny of a rice plant. Ectopic LAX expression in rice caused pleiotropic effects, including dwarfing, an altered pattern of stem elongation, darker color, bending of the lamina joint, absence of the midribs of leaves, and severe sterility.

    Original languageEnglish
    Pages (from-to)11765-11770
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Issue number20
    Publication statusPublished - Sep 30 2003

    ASJC Scopus subject areas

    • General


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