Cloning and Gene Expression Analysis of Sponge Gourd Ascorbate Peroxidase Gene and Winter Squash Superoxide Dismutase Gene under Respective Flooding and Chilling Stresses

Previously, we reported that increased ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities provide sponge gourd (SG) and winter squash (WS) plants with increased waterlogging and chilling stress tolerance, respectively. The objectives of this work were to clone the APX gene from SG and the SOD gene from WS, and measure the regulation of APX and SOD gene expressions under flooding and chilling stress, respectively. The full lengths of APX and SOD cDNA were found to be 761 and 703 bp, respectively. Different tissues from bitter melon (BM) and SG displayed wide variations in their expression profiles, and the highest level of APX transcripts were detected in roots of SG at 72 hours of flooding treatment. Additionally, the differential SOD expressions of BM and WS were directly associated with chilling stress responses. A phylogenetic analysis of APX and SOD indicated that plant APXs and SODs diverged into two major clusters.