Novel Potential Candidate Promoters and Advanced Strategies for Sugarcane Transformation

Plant transformation technology offers unique prospects to transfer a wide spectrum of functionally relevant genes in plants. Expression of genes is regulated by a number of factors among which promoter strength, specificity, and cis- and trans-acting elements play a critical role. The choice of promoter is a key determinant for the levels and specificities of gene expression. In sugarcane, the maize ubiquitin promoter has been the workhorse promoter for decades. The availability of limited promoters for sugarcane transformation is critical in sugarcane crop improvement through genetic engineering. However, recent advancements in biotechnology have provided greater insights into promoter validation from wild and commercially cultivated sugarcane, which is evident from an array of different promoters reported. This review describes the various promoters isolated from sugarcane and its wild relatives that would benefit future genetic engineering studies in sugarcane. In addition, the challenges ahead and improved strategies for sugarcane transformation are discussed.