Ursane type triterpene is one of the most widespread triterpene aglycones found in plants, together with oleanane type, and these two types often occur together in the same plant. Pisum sativum is known to produce both types of triterpenes. Homology based PCRs with degenerate primers designed from the conserved sequences found in the known b-amyrin synthases have resulted in cloning of two triterpene synthase cDNAs from immature seeds of P. sativum. They show high sequence identities to each other (78%) and also to the known b-amyrin synthases (70±90%). ORFs of the full-length clones named as PSY (2277 bp, codes for 759 amino acids) and PSM (2295 bp, codes for 765 amino acids) were ligated into the yeast expression vector pYES2 under the control of GAL1 promoter. Heterologous expression in yeast revealed PSY to be a P. sativum b-amyrin synthase. Surprisingly, however, PSM turned out to be a novel mixed amyrin synthase producing both a-and b-amyrin. Several minor triterpenes were also identified as the PSM byproducts. The presence of such multifunctional triterpene synthase would account for the co-occurence of ursane and oleanane type triterpenes in plants.

Mutations in CHCHD2 are linked to a familial, autosomal dominant form of Parkinson’s disease (PD). The gene product may regulate mitochondrial respiratory function. However, whether mitochondrial dysfunction induced by CHCHD2 mutations further yields α-synuclein pathology is unclear. Here, we provide compelling genetic evidence that mitochondrial dysfunction induced by PD-linked CHCHD2 T61I mutation promotes α-synuclein aggregation using brain autopsy, induced pluripotent stem cells (iPSCs) and Drosophila genetics. An autopsy of an individual with CHCHD2 T61I revealed widespread Lewy pathology with both amyloid plaques and neurofibrillary tangles that appeared in the brain stem, limbic regions and neocortex. A prominent accumulation of sarkosyl-insoluble α-synuclein aggregates, the extent of which was comparable to that of a case with α-synuclein (SNCA) duplication, was observed in CHCHD2 T61I brain tissue. The prion-like activity and morphology of α-synuclein fibrils from the CHCHD2 T61I brain tissue were similar to those of fibrils from SNCA duplication and sporadic PD brain tissues. α-Synuclein insolubilization was reproduced in dopaminergic neuron cultures from CHCHD2 T61I iPSCs and Drosophila lacking the CHCHD2 ortholog or expressing the human CHCHD2 T61I. Moreover, the combination of ectopic α-synuclein expression and CHCHD2 null or T61I enhanced the toxicity in Drosophila dopaminergic neurons, altering the proteolysis pathways. Furthermore, CHCHD2 T61I lost its mitochondrial localization by α-synuclein in Drosophila. The mislocalization of CHCHD2 T61I was also observed in the patient brain. Our study suggests that CHCHD2 is a significant mitochondrial factor that determines α-synuclein stability in the etiology of PD.

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A cDNA clone (GgCAS1) encoding cycloartenol synthase (CAS) has been isolated from Glycyrrhiza glabra (licorice) by cross-hybridization with that of Pisum sativum CAS as a probe. The deduced amino acid sequence of GgCAS1 exhibits 89%, 83% and 81% identity to those of Pisum sativum, Panax ginseng and Arabidopsis thaliana CASs, respectively. CAS activity has been detected in the homogenate of the yeast transformed with the expression vector containing the open reading frame of GgCAS1. Southern blot analysis suggested that at least two CAS genes exist in the licorice genome. In Northern blot analysis, the strong signal for CAS mRNA is detected in the cultured licorice cells of all growth phases, but no significant increase of CAS mRNA expression was observed in the cells treated with the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, pravastatin.

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