The role of the sucrose synthase gene in promoting thorn occurrence and vegetative growth in Lycium ruthenicum.

Lycium ruthenicum is a highly valued ecological and economic shrub, but its abundant thorns disrupt production processes. Previous studies suggested that the sucrose synthase gene (LrSUS) in L. ruthenicum may influence thorn occurrence, presenting potential for breeding thornless varieties suited for cultivation. To explore this, the full-length CDS of LrSUS was cloned, and a novel stable genetic transformation system mediated by Agrobacterium tumefaciens was developed. Through this system, both LrSUS overexpression and suppression lines were generated. While suppression lines exhibited slow growth and failed to survive post-transplant, overexpression lines demonstrated accelerated growth, with significant increases in adventitious root number and length. Upon transplanting, the overexpression lines also showed enhanced thorn occurrence, alongside notable increases in thorn length, leaf size, stem diameter, photosynthetic rate, and sugar content. Subcellular localization analysis using a transient expression method based on the injection of L. ruthenicum indicated that the LrSUS gene product is localized in the chloroplasts. Key genes involved in LrSUS/ sucrose affecting thorn occurrence event were identified through high throughput transcriptome analysis and a hypothetical mechanistic model was established. This study provides valuable insights into the function of LrSUS and establishes a foundation for manipulating thorn phenotypes in L. ruthenicum and related species.