The mevalonate diphosphate deearboxylase （MVD） is an essential enzyme in mevalonate （MVA） pathway that catalyzes the irreversible Mg2＋ -ATP de- pendent decarboxylation of 6-carben compound mevalonate-5-diphosphate （MVAPP） into 5-carbon isopentenyl diphosphate （ IPP）, the building block of sterol and isoprenoid biosynthesis. In this study, based on the published geanme sequences and ESTs, a genome-wide search was carried out for the first time to identify MVD gene family in four genome-sequenced Euphorbiaceae plants, i.e. castor bean （ Ricinus communis）, physic nut （ Jatropha curcas）, cassava （Manihot esculenta） and rubber tree （Hevea brasiliensis）, and to analyze the gene structure and phylogenetic characteristics. According to the experimental results, 1, 1,2 and 2 MVD genes, which all contain 9 introns, were identh＇ied from castor bean, physic nut, cassava and rubber tree, respectively. Homology analysis indicates that MVD genes are widely distributed in eukaryotes, some archaea and eubacteria, which suggests an early origin of this gerte family. Although MVD genes were identified in most green plants, no homologous genes were found in unicellular green algae. In most genome-sequenced plants including castor bean and physic nut, a single copy of MVD gene was found; however, in cassava and rubber tree, two copies were identified just like that in moss, maize, Arabidopsis and poplar. ＂In castor bean, digital expression profiling suggests that in five examined tissues, i.e. leaf, flower, II/III stage endosperm, V/VI stage endosperm and seed, RcPMK was expressed strongly in flower and II/III stage endosperm, moderately in V/VI stage endosperm and leaf, and weakly in seed.
Light-harvesting chlorophyll a/b-binding （LHC） proteins are a group of nuclear-encoded thylakoid proteins that play a key role in plant photosynthesis and are widely involved in light harvesting, energy transfer to the reaction center, maintenance of thylakoid membrane structure, photoprotection and response to en- vironmental conditions, etc. Although/dw supergene family is well characterized in model plants such as Arabidopsis, rice and poplar, little information is available in castor bean （Ricinus communis L. ）. In this study, a genome-wide search was carried out for the first time to identify castor bean L/w genes and analyze the gene structures, biochemical properties, evolutionary relationships and expression characteristics based on the published data of castor bean genome and ESTs. According to the results, a total of 28 Rclhcs genes representing 13 gene families （ l_hca , l_hcb , Elip , Ohpl , Ohp2 , SEP1, SEP2 , SEP3 , SEP4 , SEP5 , PsbS , Rieske and FCII） and 25 subgene families were identified in castor bean genome; to be specific, 25 and 5 genes were found to have corresponding ESTs in NCBI and have al- ternative splicing isoforlns, respectively. These RcLhcs contain 0 to 9 introns and distribute on 26 of the 25 878 released scaffolds. All RcLhcs genes were found to be expressed in all examined tissues, i.e. leaf, flower, II/III stage endosperm, V/VI stage endosperm and seed, with the highest expression level in leaf tissue.
