文部省 科学研究費補助金 新学術領域研究 植物発生ロジックの多元的開拓

PubMed ID 26020919 Pubmed 日付 2015/May/
タイトル Auxin-Mediated Transcriptional System with a Minimal Set of Components Is Critical for Morphogenesis through the Life Cycle in Marchantia polymorpha.
ジャーナル PLoS genetics  2015/May/  11(5)  e1005084 
著者 Kato Hirotaka H,Ishizaki Kimitsune K,Kouno Masaru M,Shirakawa Makoto M,Bowman John L JL,Nishihama Ryuichi R,Kohchi Takayuki T
抄録 The plant hormone auxin regulates many aspects of plant growth and development. Recent progress in Arabidopsis provided a scheme that auxin receptors, TIR1/AFBs, target transcriptional co-repressors, AUX/IAAs, for degradation, allowing ARFs to regulate transcription of auxin responsive genes. The mechanism of auxin-mediated transcriptional regulation is considered to have evolved around the time plants adapted to land. However, little is known about the role of auxin-mediated transcription in basal land plant lineages. We focused on the liverwort Marchantia polymorpha, which belongs to the earliest diverging lineage of land plants. M. polymorpha has only a single TIR1/AFB (MpTIR1), a single AUX/IAA (MpIAA), and three ARFs (MpARF1, MpARF2, and MpARF3) in the genome. Expression of a dominant allele of MpIAA with mutations in its putative degron sequence conferred an auxin resistant phenotype and repressed auxin-dependent expression of the auxin response reporter proGH3:GUS. We next established a system for DEX-inducible auxin-response repression by expressing the putatively stabilized MpIAA protein fused with the glucocorticoid receptor domain (MpIAAmDII-GR). Repression of auxin responses in proMpIAA:MpIAAmDII-GR plants caused severe defects in various developmental processes, including gemmaling development, dorsiventrality, organogenesis, and tropic responses. Transient transactivation assays showed that the three MpARFs had different transcriptional activities, each corresponding to their phylogenetic classifications. Moreover, MpIAA and MpARF proteins interacted with each other with different affinities. This study provides evidence that pleiotropic auxin responses can be achieved by a minimal set of auxin signaling factors and suggests that the transcriptional regulation mediated by TIR1/AFB, AUX/IAA, and three types of ARFs might have been a key invention to establish body plans of land plants. We propose that M. polymorpha is a good model to investigate the principles and the evolution of auxin-mediated transcriptional regulation and its roles in land plant morphogenesis.

 陸上植物におけるオーキシン転写制御系の進化

京都大学生命科学研究科 遺伝子特性学分野 河内孝之  投稿日時[2015-06-18 17:14:53]

オーキシンは植物の成長と発生を制御する主要な植物ホルモンである。その応答には転写制御系が重要であることが示されてきたが、どのように進化的に獲得されたかは不明であった。本研究では、陸上植物の基部に位置する苔類のモデルであるゼニゴケが、オーキシン受容体(MpTIR1)、各クラスのARF転写制御因子(Mp ARF1, ARF2, ARF3)、抑制因子(MpIAA)といった最低限の制御因子セットを用いて、生活環を通じて多様な応答を行っていることを示した。つまり、既に陸上植物の共通の祖先でオーキシン転写制御系が成立し、陸上植物のボデイプランにおける役割を果たしていたことが示された。