Isolation and characterization of a new d-limonene synthase gene with a different expression pattern in Citrus unshiu Marc

We isolated a new d-limonene synthase gene (CitMTSE2) from Satsuma mandarin (Citrus unshiu Marc.) and compared its mRNA expression pattern with that of the previously isolated CitMTSE1. The predicted protein of CitMTSE2 showed 84.2% identity to that of CitMTSE1 at the amino acid level and possessed the typical structure and chemical features of general monoterpene synthases, such as transit peptides in the N-terminus, sequence motifs of RR and DDXXD, and cation-dependent reactions. A functional test demonstrated that CitMTSE2 is a d-limonene synthase gene. Under different expression regulations in response to the fruit developmental stage, the mRNA expression of CitMTSE2 indicated a specificity to fruit tissue and was different from that of CitMTSE1 Occurring mainly in peel at an early stage of fruit development, the mRNA expression profile of CitMTSE2 was similar to that of d-limonene biosynthesis in C. unshiu. (c) 2005 Elsevier B.V. All rights reserved.