Abstract: Here cloning the ScAPX1 of sugarcane and analyzing its expression under low temperature stress is to provide a basis for further studying the function of APX1 gene in sugarcane under low temperature stress and investigating the molecular mechanism of breeding cold stress-resistant sugarcane. Having total RNA of sugarcane leaf as template,RT-PCR technique was used to clone the complete ORF sequence of ScAPX1 from sugarcane leaf,bioinformatics software was to analyze the characteristics of the encoding protein,and quantitative real-time PCR（qRT-PCR）method was applied to study the expressions of ScAPX1 gene under low temperature stress in two sugarcane varieties GT28 and YL6 with widely different cold resistance. The results showed that the ScAPX1 gene（GenBank accession number：KC794939）in sugarcane was cloned,which contained a complete open reading frame of 759 bp and encoded 252 amino acids. The protein encoded by this gene contained no signal peptide and no transmembrane structure,was a soluble protein and located in cytoplasm,and its homology with sorghum amino acid was 98%. It was inferred that ScAPX1 gene was a cytoplasmic ascorbic acid peroxidase gene（ScAPX）. qRT-PCR analysis showed that with the extension of low temperature（0-4^oC）,the expression levels of ScAPX1 gene in two sugarcane varieties increased first and then decreased,but differed. In the whole process of cold stress,the relative expression level in GT28,a cold resistant variety,was always higher than that in YL6,a cold sensitive variety. This result suggests that the ScAPX1 gene of sugarcane is active in response to low temperature stress,and the induced expression of this gene is closely related to the cold resistance of sugarcane varieties.

Key words: sugarcane, ScAPX1, gene cloning, low temperature stress, expression analysis