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<p>Sucrose phosphate synthase (SPS) is a pivotal enzyme in the sucrose biosynthesis pathway that regulates carbon partitioning between source and sink tissues in plants. Despite its recognized importance, the <i>in planta</i> role of individual <i>OsSPS</i> isoforms in rice remains poorly defined. In this study, we used CRISPR/Cas9 to generate targeted knockout (KO) mutants of <i>OsSPS1</i> and <i>OsSPS2</i> in <i>Oryza sativa</i> (cv. Dongjin) to investigate the physiological, metabolic, and agronomic consequences of SPS deficiency. Homozygous KO lines were confirmed by Sanger sequencing and exhibited severe reductions in <i>OsSPS</i> transcript levels, as validated by qRT-PCR. Metabolite profiling revealed a significant decrease in sucrose content (− 60%) and concomitant increases in glucose (+ 1.9-fold) and fructose (+ 2.2-fold) levels in KO lines, indicating disruption of sucrose biosynthesis and altered sugar partitioning. Moreover, KO plants exhibited impaired photosynthetic efficiency, reduced chlorophyll fluorescence (Fv/Fm), and stunted vegetative growth. Expression of sugar transporter genes (<i>OsSUT1</i>, <i>OsSWEET11</i>) and nitrogen assimilation genes (<i>OsGS1</i>, <i>OsNRT2.1</i>) was also downregulated, suggesting coordinated repression of carbon and nitrogen transport systems. Importantly, agronomic traits such as panicle number, grain filling rate, and thousand-grain weight were significantly reduced in KO lines, confirming the essential role of <i>OsSPS</i> in supporting source–sink communication and reproductive development. These findings demonstrate that <i>OsSPS</i> genes are central regulators of sugar allocation, photosynthesis, and productivity in rice. This study provides genetic and physiological evidence for the functional significance of SPS in crop yield determination and may offer a basis for future metabolic engineering strategies aimed at improving carbon use efficiency.</p>

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CRISPR/Cas9 knockout of OsSPS impairs sugar allocation and growth in rice (Oryza sativa L.)

  • 期刊论文

  • 发表日期：

    2026年2月24日

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  • Jin Young Kim,
  • Yu-Jin Jung,
  • Hye Mi Lee,
  • Kwon Kyoo Kang

摘要

Sucrose phosphate synthase (SPS) is a pivotal enzyme in the sucrose biosynthesis pathway that regulates carbon partitioning between source and sink tissues in plants. Despite its recognized importance, the in planta role of individual OsSPS isoforms in rice remains poorly defined. In this study, we used CRISPR/Cas9 to generate targeted knockout (KO) mutants of OsSPS1 and OsSPS2 in Oryza sativa (cv. Dongjin) to investigate the physiological, metabolic, and agronomic consequences of SPS deficiency. Homozygous KO lines were confirmed by Sanger sequencing and exhibited severe reductions in OsSPS transcript levels, as validated by qRT-PCR. Metabolite profiling revealed a significant decrease in sucrose content (− 60%) and concomitant increases in glucose (+ 1.9-fold) and fructose (+ 2.2-fold) levels in KO lines, indicating disruption of sucrose biosynthesis and altered sugar partitioning. Moreover, KO plants exhibited impaired photosynthetic efficiency, reduced chlorophyll fluorescence (Fv/Fm), and stunted vegetative growth. Expression of sugar transporter genes (OsSUT1, OsSWEET11) and nitrogen assimilation genes (OsGS1, OsNRT2.1) was also downregulated, suggesting coordinated repression of carbon and nitrogen transport systems. Importantly, agronomic traits such as panicle number, grain filling rate, and thousand-grain weight were significantly reduced in KO lines, confirming the essential role of OsSPS in supporting source–sink communication and reproductive development. These findings demonstrate that OsSPS genes are central regulators of sugar allocation, photosynthesis, and productivity in rice. This study provides genetic and physiological evidence for the functional significance of SPS in crop yield determination and may offer a basis for future metabolic engineering strategies aimed at improving carbon use efficiency.