A Review of the Diverse Genes and Molecules Involved in Sucrose Metabolism and Innovative Approaches to Improve Sucrose Content in Sugarcane

Sugarcane (<i>Saccharum</i> spp. hybrid) is the chief source of sugar and biofuel globally and is prominent among cash crops. Sucrose is the main required product in sugarcane, and many studies have been performed to understand the phenomena of sucrose synthesis, metabolism, and accumulation in sugarcane. However, none of the studies concluded that a single gene is responsible for the sucrose content. Instead, a complex mechanism consisting of several genes, such as sucrose phosphate synthase genes (<i>SPS1</i>, <i>SPS2</i>, <i>SPS4</i>, <i>SPS5</i>), sucrose synthase genes (<i>SuSy1</i>, <i>SuSy2</i>, <i>SuSy4</i>), invertase genes (<i>INV</i>, <i>CWIN</i>, <i>NIN1</i>, <i>CINV2</i>), and phytohormone, trehalose, transcription factor (TF), protein kinase, and sugar transporter genes are working spatiotemporally in sugarcane. Currently, omics approaches like transcriptomics, proteomics, and metabolomics are also being used to explore the sugar metabolism in sugarcane, but integrated transcriptomic, proteomic, and metabolomic studies have been less reported. The results obtained from the integrated analysis of transcriptomics, proteomics, and metabolomics are more reliable because the strong gene expression, received in the form of abundant mRNA, does not guarantee the plentiful existence of associated proteins or their particular activity in the target cells or tissues, which discloses the restraint of single interpretation and stresses the significance of the integrated analysis of transcriptomics, proteomics, and metabolomics. This review highlights different genes and molecules contributing to sugar metabolism at different stages and the significance of omics approaches in explaining sucrose metabolism, especially sucrose accumulation in sugarcane. It is also a vital source of knowledge for sugarcane breeders, particularly associated with sucrose content improvement and bioethanol energy production.