Excavation and Functional Verification of Plant Height Gene BnGPI2-A03 in Brassica napus L.

Plant height is an important agronomic trait that affects the establishment of the ideal plant type and yield formation of rapeseed. However, the genetic mechanism affecting plant height has not been fully elucidated. Building on previous genome-wide association studies (GWASs), we performed differential gene expression analysis using 14 shoot apex transcriptome datasets derived from materials exhibiting extreme seedling height phenotypes at the bud stage. The promoter and the first exon regions of the Glycosylphosphatidylinositol 2 gene (BnGPI2-A03) of rapeseed were identified as harboring two significant SNPs (Bn-A03-p717776 and Bn-A03-p7178917) associated with plant height. Co-expression network analysis shows that BnGPI2-A03 was associated with many hormone pathway genes, cell wall synthesis pathway genes, and transcription factor genes and formed a potential network regulating the plant height of rapeseed. To examine the function of BnGPI2-A03 on plant height in Brassica napus L., we generated transgenic plants in which BnGPI2-A03 was overexpressed using a 35 s promoter. Overexpression of BnGPI2-A03 elevated the height and main inflorescence length of the transgenic plant by an average of 17.95% and 25.92%, respectively, which showed a positive relationship with the level of BnGPI2-A03. Transcriptome sequencing analysis of the overexpressed transgenic rapeseed stem-tip tissue during the bud stage shows that BnGPI2-A03 is associated with plant cell wall synthesis and cell division pathways. The requirement of BnGPI2-A03 for plant height was further evidenced in natural germplasms by the higher expression levels of BnGPI2-A03 in the stem-tip tissue of extremely high genotypes (Hap1) relative to their ultra-short counterparts (Hap3). These discoveries highlight potential targets for the plant height genetic improvement of rapeseed in the future.