This review deals with the biological aspects of monoterpene biosynthesis with special reference to the genetic nature of chemical variations (chemotypes) and a number of genes controlling biosynthetic reaction steps leading to the terpenoid components of essential oils in Perilla frutescens. Genetic analyses revealed the existence of two dominant genes of basic importance: gene G required for the induction of the whole monoterpene biosynthesis and gene H controlling a monoterpene cyclase (limonene synthase) necessary for the formation of cyclic monoterpenes. The nature and biochemical roles of these interesting genes are discussed in detail.
Somatic embryogenesis in Cryptomeria japonica was initiated at a relatively high frequency from immature seeds collected from the end of June to mid-July. Induction of embryogenic cultures was possible on media with or without plant growth regulators, and the initiation frequency varied from 5 to 16%. Embryogenic cell lines have been maintained and proliferated for more than 2 years in solid and liquid media. For long-term storage embryogenic cells were cryopreserved using a simple freezing method. Cotyledonary embryos were obtained mostly on maturation media containing abscisic acid (ABA) and polyethylene glycol (PEG) as osmotic agent, however, the plant conversion rate was still low. Plants regenerated from somatic embryos continued growing in a greenhouse. Furthermore, a procedure for the individual culture of protoplasts isolates from embryonal masses, and an approach for microprojectile bombardment-mediated transformation using pIPT and pMAT vectors was also described.
The type I element (CCACGTCACCAATCCGCG) is a cis-acting element essential for cell cycle-dependent expression of the wheat histone H3 gene (TH012). This element consists of two distinct motifs, Hex (CCACGTCA) and Oct (CGCGGATT). To understand the mechanism of transcriptional regulation via the type I element, we analyzed the function of HBP-1b (c38), a Hex-motif-specific DNA-binding protein of wheat, by using a transient expression system. Cotransfection experiments with effector and reporter plasmids indicated that overexpressed HBP-1b (c38) did not activate expression of the reporter gene with a normal type I element but unexpectedly enhanced the activity of the promoter with a mutated Hex-motif-containing type I element. This activation was Oct-motif-dependent. Basic, leucine zipper, and acidic regions of the HBP-1b (c38) protein were necessary for this activation. These results suggest that HBP-1b (c38) has an ability to activate transcription without interacting with a target DNA sequence.
Maize seedlings were irradiated with 20Ne8+ generated by the AVF cyclotron. The growth suppression at the different dosages of ion beam was observed in both root and coleoptile. DNA laddering was also observed at the dosage over 100Gy. In addition, abnormal morphological changes including chromatin condensation, typical of apoptosis in animal cells, were noted by light and electron microscopy. Our results indicate that the ion beam can serve as an effective tool to induce apoptosis-like cell death in plant cells.
Delila protein is a member of MYC-like transcriptional activator family, which regulates the expression of structural genes in the biosynthesis of anthocyanin in snapdragon. We have mutated several amino acid of Delila to elucidate their function using transcriptional activation by yeast one-hybrid system. Among several site-directed mutations, the replacement of alanine-161 with 18 different amino acids resulted in severe decrease in the transcriptional activation of the yeast GAL1 promoter Delila fused to the yeast GAL4 DNA-binding domain. This lack of induction indicates the importance of alanine-161 for transcriptional activation by Delila protein. Although the mutational change at residue 161 from alanine to aspartic acid exhibited no activity, the deletion of N-terminus (1-136 amino acids) of this mutant resulted in the recovery of activity. These results suggest that alanine-161 located outside the activation domain in Delila plays a critical role for its transcriptional activation in yeast.
Transcriptomes of the developing seeds of high-oleate and high-linoleate strains of safflower (Carthamus tinctorius) were compared using a fluorescent differential display technique. Two cDNA fragments (O1-1 and O2-3) were identified as the bands originated from the genes highly or specifically expressed in the developing seeds of the high-oleate safflower. A cDNA clone, CTOS-1, encoding a novel protein with an isoprenoid binding site at the C-terminus was isolated by screening a cDNA library constructed from the developing seeds of high-oleate safflower using the O2-3 fragment as a probe. Northern blot analysis indicated that CTOS-1 gene expresses only in the developing seeds of the high-oleate safflower. The transcript cannot be detected either in the developing seeds of the high-linoleate safflower nor in the leaves, stems and flower buds of the two strains. Southern blot analysis using the CTOS-1 cDNA as a probe indicated the presence of restriction fragment length polymorphism between the high-oleate and high-linoleate strains.
Biotransformation of paclitaxel by cell suspension cultures of Marchantia polymorpha was studied and it was found that liverwort cultures convert paclitaxel to 7-epi-paclitaxel in good yield and regioselectively hydrolyses the ester group at the 10-position of paclitaxel.
A nearly full-length PAL cDNA clone was isolated from petals of carnation (Dianthus caryophyllus). Northern analysis revealed that the cDNA obtained here as a probe gave a strong signal corresponding to PAL transcripts prepared from petals, but weak signals in young and old leaves, stems and roots. The amount of PAL transcripts in petals increased with development from small buds to opening flowers, along with the accumulation of anthocyanin in petals. This is the first report of a PAL cDNA clone derived from petals.
The cDNA clone, TAN1, encoding anthocyanidin synthase (ANS) was isolated by screening of a cDNA library constructed from flower petals of Torenia fournieri cv. Summer Wave Blue using a heterologous probe. Nucleotide sequence analysis revealed that it contains an open reading frame encoding a polypeptide of 376 amino acids. The postulated amino acid sequence shows 48% to 72% identities with those of previously reported ANSs. Southern blot analysis suggested that there is a single copy of ANS gene in the genome of T. fournieri. Northern blot analysis indicated that ANS gene is expressed in flower bud but not in leaf or mature flower.
A cDNA coding a putative ribosome-inactivating protein (CF-RIP) from Cucumis figarei has been cloned and sequenced. The entire cDNA contains an ORF encoding a protein of 286 amino acids which shares conserved residues for ribosome-inactivating proteins (RIPs). CF-RIP shares 54.8-64.5% identity with four RIPs from other cucurbits. RT-PCR analysis indicated that CF-RIP mRNA was expressed in leaf and stem tissues of C. figarei.