Cloning of sugarcane <italic>ScCRT1</italic> gene and its response to SCMV infection

Abstract

<p indent=0mm>Calreticulin (CRT) is widely expressed in eukaryotes. As a molecular chaperone and a Ca²⁺ binding protein, CRT is involved in many biological pathways such as the regulation of calcium homeostasis, calcium-dependent signaling, endoplasmic reticulum quality control, plant growth and development, immunity and response to stress. However, the response of <italic>CRT</italic> of sugarcane (<italic>Saccharum</italic> spp. hybrid) challenged by <italic>Sugarcane mosaic virus</italic> (SCMV) has not been reported. In this study, a <italic>CRT</italic> gene was cloned from the noble cane cultivar Badila (<italic>S</italic>.<italic> officinarum</italic>) and designed as <italic>ScCRT1</italic>. <italic>ScCRT1</italic> had an open reading frame (ORF) length of <sc>1281 bp</sc> and encoded 426 amino acids. Bioinformatics analysis showed that ScCRT1 was a stable hydrophilic protein and possesses a signal peptide at the N-terminal, a typical transmembrane domain, and a typical endoplasmic reticulum location signal at the C-terminal. The secondary structure of ScCRT1 was composed of mostly random coils. Phylogenetic tree analysis indicated that ScCRT1 belonged to the CRT1/CRT2 subtype and was divergent between monocotyledons and dicotyledons. Subcellular location assays showed that ScCRT1 was mainly located in the endoplasmic reticulum. Real-time quantitative PCR analysis showed that <italic>ScCRT1</italic> gene was extensively expressed in different tissues of sugarcane, with the highest expression in leaf roll and the lowest expression in the 8th internode. <italic>ScCRT1</italic> gene was up regulated in the early stage of SCMV infection, but down regulated with time going. ScCRT1 interacted with the 6K2 from SCMV as confirmed by yeast two hybrid and bimolecular fluorescence complementation assays. Based on these foundlings, we speculated SCMV interfered the calcium homeostasis by the interaction of 6K2 with ScCRT1, thereby facilitating viral infection of sugarcane.