Identification and Functional Analysis of Strigolactone Pathway Genes Regulating Tillering Traits in Sugarcane

Abstract Saccharum officinarum (S. officinarum) and Saccharum spontaneum (S. spontaneum) are two fundamental species of modern sugarcane cultivars, exhibiting divergent tillering patterns crucial for sugarcane architecture and yield. Strigolactones (SLs), a class of plant hormones, are considered to play a central role in shaping plant form and regulating tillering. Our study highlights the distinct tillering patterns observed between S. officinarum and S. spontaneum, and implicates significant differences in SL levels in root exudates between the two species. Treatment with rac-GR24 (an artificial strigolactone analog) suppressed tillering in S. spontaneum. Based on transcriptome analysis, we focused on two genes, TRANSCRIPTION ELONGATION FACTOR 1 (TEF1) and CIRCADIAN CLOCK ASSOCIATED1 (CCA1), which show higher expression in S. spontaneum or S. officinarum, respectively. While the overexpression of SoCCA1 did not lead to significant phenotypic differences, overexpression of SsTEF1 in rice stimulated tillering and inhibited plant height, demonstrating its role in tillering regulation. However, the overexpression of suggesting that SoCCA1 may not be the key regulator of sugarcane tillering. Yeast one-hybrid (Y1H) assays identified four transcription factors (TFs) regulating SsTEF1, four and five TFs regulating SsCCA1 and SoCCA1. This study provides a theoretical foundation for deciphering the molecular mechanisms underlying the different tillering behaviors between S. officinarum and S. spontaneum, providing valuable insights for the molecular-based design of sugarcane breeding strategies.