Isolation and characterization of two cDNAs encoding translation initiation factor 1A from rice(Oryza sativa L.).

The eukaryotic initiation factor 1A(eIF1A) is essential for transferring of the initiator Met-tRNA to 40S ribosomal subunits to form the 40S pre-initiation complex. In present study, we describe the cloning and characterization of two eIF1A genes from rice, which were designated as Oryza sativa eukaryotic initiation factor 1A genes OseIF1A-1, OseIF1A-2, respectively. Both rice elF1As shared high identities in amino acids with eIF1A proteins from other eukaryotes. The mRNA expression analysis revealed that OseIF1A-2 mRNA was much more accumulated than OseIF1A-1 in all tissues but each gene is expressed in root, stem, leaf and flowering spike in high and nearly equal level, and in immature spike in lower level. These results, together with their different location in unrooted phylogenetic tree inferred from amino acid sequences of all known eIF1As, suggested that there are two types of eIF1A genes with different function or different regulation in rice.     

Molecular cloning and characterization of a gene regulating flowering time from Alfalfa (Medicago sativa L.)

Genes that regulate flowering time play crucial roles in plant development and biomass formation. Based on the cDNA sequence of Medicago truncatula (accession no. AY690425), the LFY gene of alfalfa was cloned. Sequence similarity analysis revealed high homology with FLO/LFY family genes of other plants. When fused to the green fluorescent protein, MsLFY protein was localized in the nucleus of onion (Allium cepa L.) epidermal cells. The RT-qPCR analysis of MsLFY expression patterns showed that the expression of MsLFY gene was at a low level in roots, stems, leaves and pods, and the expression level in floral buds was the highest. The expression of MsLFY was induced by GA₃ and long photoperiod. Plant expression vector was constructed and transformed into Arabidopsis by the agrobacterium-mediated methods. PCR amplification with the transgenic Arabidopsis genome DNA indicated that MsLFY gene had integrated in Arabidopsis genome. Overexpression of MsLFY specifically caused early flowering under long day conditions compared with non-transgenic plants. These results indicated MsLFY played roles in promoting flowering time.     

Isolation of triterpenoid saponins from Medicago sativa L. with neuroprotective activities

Three new pentacyclic triterpenoid saponins (1–3), together with medicagenic acid (4) were isolated and purified from 70% EtOH extract of Medicago sativa L. by different column chromatographic and semi-preparative HPLC. Their structures were established by direct interpretation of their spectral data, mainly HR-ESI-MS, 1D-NMR, 2D-NMR, and chemical methods, as well as comparison with literature data. Additionally, all isolates were evaluated for their neuroprotective activities against H₂O₂-induced damage in human neuroblastoma SHSY5Y cells. As a results, compounds 1 and 2 (67.14% and 73.05%) exhibited potent neuroprotective activities. These findings provide new insights into developing better treatment of neurodegenerative diseases for M. sativa in the future.     

Isolation and Identification of Endogenous Cytokinins from Alfalfa (Medicago sativa L)

Endogenous cytokinins in alfalfa were isolated, and identified by mass spectrometry, trans- Ribosylzeatin (RZ) and ribosyldihydrozeatin (DHRZ) were identified from the root, and the combined content (benzyladenine equivalent) was estimated to be approximately 0.5/μg/100 g of fresh weight, eis- and trans-KL were identified from the stems and leaves. The relative content of the m-isomer was approximately five times greater than that of the trans-isomer.     

Regeneration and characterization of plants obtained from anther cultures in Medicago sativa L

Summary The androgenic ability of four Medicago sativa L. genotype (Boynitza 5, Byala, 494, and 3815) was tested. Callus and organogenesis were induced in all lines studied. The percentage of anthers producing calluses and organogenesis showed wide variation (calluses—from 11% up to 77%; organogenesis—4.8% to 15.2%). It has been established that genotype, nutrient medium composition, and stage of pollen development considerably affected both callus production and organogenesis. Androgenesis in M. sativa could be achieved via callus and direct embryogenesis. About 500 morphologically different regenerants were obtained. Wide variability in chromosome number of regenerated plants was observed by cytological studies. Haploid, dihaploid, as well as mixoploid plants were obtained.     

Isolation and characterization of the structural gene encoding elongation factor 3

The unique yeast translational factor EF-3 participates in the elongation cycle by stimulating the function of EF-1 alpha in binding aminoacyl-tRNA to the ribosome. We have isolated the structural gene encoding EF-3 from the yeast Saccharomyces cerevisiae. The YEF3 gene is found in one copy per haploid genome and is essential for vegetative growth. DNA sequence analysis reveals that the YEF3 gene contains an open reading frame of 1044 codons. The deduced amino acid sequence has two repeats of a nucleotide-binding motif. Each of these repeats shows similarity to the nucleotide-binding motif of hydrophilic, membrane-associated ATPases including human multidrug resistant protein MDR. Factor 3 manifests ribosome-dependent ATP hydrolysis. Introduction of the YEF3 gene on a high copy number plasmid into yeast strains increases the ribosome-dependent ATPase activity and EF-3 protein levels by 3-5-fold. Yeast strains containing elevated EF-3 protein levels also exhibit increased sensitivity to the aminoglycoside antibiotics hygromycin and paromomycin. These drugs are known to increase translational errors. These observations suggest that EF-3 may affect translational accuracy.