ISOLATION AND EXPRESSION PATTERN OF COR15B AND KIN1 GENES IN WATERMELON AND SQUASH

Abstract

COR15b and KIN1 (COR 6.5) genes encode polypeptides of 15 KDa and 6.5 KDa, respectively. They are involved in the dehydration tolerance mechanisms, and play important role under cold stress. cDNA sequences of COR15b and KIN1 genes were firstly isolated from leaves of watermelon (Citrullus lanatus) and squash (Cucurbita moschata). Sequencing results indicated that the open reading fragments (ORF) of COR15b in watermelon (ClCOR15b) and COR15b in squash (CmCOR15b) were 348 and 426 bp, which encoded 116 and 141 amino acids, respectively. The putative amino acids of CmCOR15b shared 98.58% identities to COR15b in Arabidopsis (AtCOR15b), but ClCOR15b had only 80.85% identities to AtCOR15b because there appeared two mutations at the positions of 220 (C/T) and 418 (T/A) in ClCOR15b and T/A mutation produced a transcript end codon (TAA), which led to a lack of 26 amino acids. Similar to KIN1 in Arabidopsis (AtKIN1), ORFs of both KIN1 in watermelon (ClKIN1) and KIN1 in squash (CmKIN1) were 198 bp, encoding two short polypeptides of 65 amino acids. The putative amino acids of CIKIN1 and CmKIN1 shared 98.48 and 90.51% identities to AtKIN1, respectively, although they also contained some mutation sites. Real-time quantitative PCR results indicated that, during cold stress condition, transcripts of CmCOR15b, ClKIN1 and CmKIN1 increased significantly, suggesting that they could take part in the cold tolerance. However, C1COR15b kept stable during cold stress, implying that its role during cold stress could be changed because of the lacked sequence.