Isolation and characterization of curcin genes with distinct expression patterns in leaves and seeds of Jatropha curcas L.

Jatropha (Jatropha curcas L.) is an emerging biofuel plant, of which its seed oil is suitable for biodiesel production. Curcin, a type 1 ribosome inactivating protein, is the major toxic protein found in jatropha seeds. Here we report the cloning and characterization of three curcin genes from J. curcas MD44. The Curcin 1 (C1) gene encodes a Type I curcin precursor containing 293 amino acid residues. The C1 gene is specifically expressed in the endosperm of jatropha seeds at late developmental stage. The Curcin 2A (C2A) gene encodes a Type II curcin precursor containing 309 amino acid residues and is mainly expressed in young leaves of J. curcas. The Curcin 2B (C2B) gene is another Type II curcin gene that is physically linked to the C1 gene. However, the expression of the C2B gene was not detected in leaves or seeds of jatropha plants growing under normal growth condition. A conserved 227-bp or 228-bp intron was identified or predicted in the 5′ untranslated region of the three curcin genes. A C1 promoter (−2888bp to +293bp) was identified to harbor all cis-elements that are required for full promoter activity in jatropha endosperm. The isolation of the three curcin genes and the endosperm-specific C1 promoter provide useful information and research materials for further functional study of curcin proteins and genetic engineering of J. curcas.