Identification of calreticulin and calnexin gene families in sugarcane and mechanistic elucidation of their roles in response to SCMV infection

• ScCRT and ScCNX family members from the sugarcane cultivar XTT22 were identified. • CNXs interacts with potyviral 6K2, whereas CRTs do not. • Transient expression of ScCNX1-1 or silencing of NbCNXs inhibited TuMV infection. • ScCNX1-1 is a potential target for engineering SCMV resistance in sugarcane. Sugarcane mosaic disease, primarily caused by sugarcane mosaic virus (SCMV), seriously affects sugarcane production. The 6K2 protein is crucial for potyvirus infection. Calnexin (CNX) and calreticulin (CRT) play key roles in plants growth, development, and response to stresses. However, the CRT and CNX families have not been studied in sugarcane. Here, we screened CNX from a sugarcane cDNA yeast library with 6K2 of SCMV as bait. We identified 65 ScCRTs and 11 ScCNXs from the sugarcane cultivar XTT22, which were phylogenetically classified into three groups. The promoter regions of these genes contain multiple cis -elements related to growth and development, environmental stress, plant hormone responses, and light responses. Transcriptomic analysis revealed differential spatiotemporal expression of ScCRTs and ScCNXs . We cloned four CRT and one CNX genes from XTT22, which localized to the endoplasmic reticulum. ScCNX1-1 was differentially expressed in sugarcane tissues and was upregulated upon SCMV infection. Protein–protein assays demonstrated that only ScCNX1-1 interacts with SCMV-6K2. Transient expression of ScCNX1-1 in Nicotiana benthamiana suppressed turnip mosaic virus (TuMV) infection. Moreover, all four CNXs, but not the CRTs from N. benthamiana , interacted with TuMV-6K2. Transient NbCNX silencing inhibited TuMV infection. These findings indicate that the interaction of CNX with 6K2 is a conserved mechanism for potyvirus infection, and that CNX expression is fine-tuned and tightly controlled upon viral infection. This study sheds light on the roles of ScCRT and ScCNX genes in sugarcane growth, development, and response to stresses, and provides a potential molecular target for engineering SCMV resistance in sugarcane.