Cloning and characterisation of two genes for 3-hydroxy-3-methylglutaryl coenzyme A reductase and their possible roles during fruit development in Dimocarpus longan.

摘要

3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR; EC: 1.1.1.34), encoded by multiple genes in eukaryotes, is known to catalyse the 1st committed step in the mevalonic acid pathway for biosynthesis of isoprenoids, and has been implicated in fruit size determination. To elucidate whether genes for HMGR are involved in regulation of fruit growth in longans, 2 sequence-distinct HMGR genes, designated DlHMG1 and DlHMG2, were cloned. Sequence analyses revealed that they shared a high level of sequence and domain conservation with homologues identified in other species at the nucleotide and amino acids levels. Gene expression analysis showed that the 2 genes were differentially regulated in the pericarp, arils and seed, as well as during fruit development. DlHMG1 was up-regulated particularly in Phase I (0-42 days after anthesis (DAA)) and at the early stage of Phase II (42-56 DAA), followed by down-regulation in Phase III (>=56 DAA); while DlHMG2 was expressed constitutively in the pericarp and arils, but fluctuated periodically in seeds during fruit development. Possible roles of DlHMG1 and DlHMG2 in the regulation of longan fruit size and growth are discussed.