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<p>Cytokinin (CK) and gibberellin (GA) act antagonistically to shape plant architecture, promoting shoot branching and stem elongation, respectively. Here, we identify the barley AP2/ERF transcription factor HvRAF as a positive regulator for tillering and moderate semi-dwarfism. <i>HvRAF</i>-overexpressing (<i>HvRAF</i> OE) plants exhibited earlier tiller emergence, increased tiller number, and reduced plant height associated with shortened stem internodes compared with the wild-type. To uncover the underlying mechanism, we examined the gene expression of CK and GA related genes. <i>HvRAF</i> OE plants showed significantly enhanced expression of adenosine phosphate–isopentenyltransferase (<i>OsIPT</i>) family genes and <i>LONELY GUY</i> (<i>OsLOG</i>), while down-regulating CK degradation genes (<i>OsCKX</i> family) and negative CK signaling regulators, type-A response regulators (<i>OsRR4</i> and <i>OsRR6</i>), indicating that HvRAF enhanced CK biosynthesis and signaling. By contrast, HvRAF specifically modulated late steps of GA metabolism. Transcripts of GA-activating enzymes, GA 20-oxidases (OsGA20ox) and OsGA3ox, were reduced, whereas those of the GA-deactivating enzyme OsGA2ox were induced, without significant changes in the expression of early GA biosynthetic or GA signaling genes. Consistently, bioactive GA₁ and its 13-hydroxylation precursors were decreased in <i>HvRAF</i> OE plants. Field evaluations under normal paddy conditions showed that <i>HvRAF</i> OE lines produced more effective tillers and panicles, resulting in increased spikelet number and grain yield per plant without penalties in fertility or grain filling. These findings demonstrate that HvRAF is a promising dominant regulator that rebalances CK and GA pathways to optimize rice plant architecture and enhance yield potential.</p>

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The barley ERF factor HvRAF enhances tillering and grain yield in transgenic rice by modulating cytokinin–gibberellin homeostasis

  • 期刊论文

  • 发表日期：

    2026年1月6日

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  • Jaemin Hwang,
  • Sang-Mo Kang,
  • Eun-Hae Kwon,
  • In-Jung Lee,
  • Jun Sung Seo,
  • Minkyun Kim

摘要

Cytokinin (CK) and gibberellin (GA) act antagonistically to shape plant architecture, promoting shoot branching and stem elongation, respectively. Here, we identify the barley AP2/ERF transcription factor HvRAF as a positive regulator for tillering and moderate semi-dwarfism. HvRAF-overexpressing (HvRAF OE) plants exhibited earlier tiller emergence, increased tiller number, and reduced plant height associated with shortened stem internodes compared with the wild-type. To uncover the underlying mechanism, we examined the gene expression of CK and GA related genes. HvRAF OE plants showed significantly enhanced expression of adenosine phosphate–isopentenyltransferase (OsIPT) family genes and LONELY GUY (OsLOG), while down-regulating CK degradation genes (OsCKX family) and negative CK signaling regulators, type-A response regulators (OsRR4 and OsRR6), indicating that HvRAF enhanced CK biosynthesis and signaling. By contrast, HvRAF specifically modulated late steps of GA metabolism. Transcripts of GA-activating enzymes, GA 20-oxidases (OsGA20ox) and OsGA3ox, were reduced, whereas those of the GA-deactivating enzyme OsGA2ox were induced, without significant changes in the expression of early GA biosynthetic or GA signaling genes. Consistently, bioactive GA₁ and its 13-hydroxylation precursors were decreased in HvRAF OE plants. Field evaluations under normal paddy conditions showed that HvRAF OE lines produced more effective tillers and panicles, resulting in increased spikelet number and grain yield per plant without penalties in fertility or grain filling. These findings demonstrate that HvRAF is a promising dominant regulator that rebalances CK and GA pathways to optimize rice plant architecture and enhance yield potential.