Structure, Intracellular Localisation and Expression Analysis of Sucrose Nonfermenting-Related Kinase ShSnRK1α in Sugarcane

Sucrose nonfermenting-related kinase 1 (SnRK1) function as a key regulator in sensing sucrose-Tre6P (trehalose 6-phosphate) signalling and negatively regulating sucrose homeostasis and content in plants. To clarify the potential functions of SnRK1 in sugarcane, we isolated a SnRK1 catalytic α subunit gene ShSnRK1α from sugarcane. The structure conservation, intracellular localisation and gene expression of ShSnRK1α were analysed. Results showed that ShSnRK1α had a 1527 bp open reading frame encoding 509 amino acids. The protein sequence of ShSnRK1α contained three conserved domains, including an N-terminal catalytic protein-kinase domain, a middle-plant-specific ubiquitin associated (UBA) domain and a C-terminal regulatory (αCTD) domain. The N -terminal protein-kinase domain of ShSnRK1α was highly conserved in SnRK1αs from monocot and dicot plant species. The UBA and αCTD domains of ShSnRK1α had sugarcane specificity. ShSnRK1α shared high identity with SnRK1αs from sorghum, maize and rice. Intracellular localisation analysis showed that ShSnRK1α localised in the nucleus and cytoplasm regions of rice mesophyll protoplasts. Expression analysis showed that ShSnRK1α was constitutively expressed in sugarcane leaves and stem internodes. ShSnRK1α was more highly expressed in sucrose rapid-accumulation maturing internodes than in immature and mature internodes. Meanwhile, ShSnRK1α was expressed lower in leaves and sucrose accumulating internodes of high-sugar-content sugarcane plants than that of low-sugar-content sugarcane plants. Thus, ShSnRK1α may play an important role on regulating sucrose homeostasis and accumulation in sugarcane. This study provided a target to clarify the sugar-accumulation regulating mechanism of sugarcane and improve its sugar content.