Chemistry of medicinal plants (review)]

Data on the chemical composition related to synthesis of physiologically active substances (alkaloids, terpenoids, glycosides, phenolic compounds, etc.), and accumulation of individual elements or groups of five to ten elements (e.g., Cr, Co, Mn, and Zn) in medicinal plants were reviewed. Chemical features of medicinal plants serve as an integral determinant of their species specificity and pharmacological properties and enabling their wide use in medical practice. The relationship between the synthesis of physiologically active substances and accumulation of elements is mediated by several levels of molecular regulation.     

Cloning and characterization of chromosomal markers in alfalfa (Medicago sativa L.)

Eleven tandemly repetitive sequences were identified from a Cot-1 library by FISH and sequence analysis of alfalfa (Medicago sativa). Five repetitive sequences (MsCR-1, MsCR-2, MsCR-3, MsCR-4, and MsCR-5) were centromeric or pericentromeric, of which three were satellite DNAs and two were minisatellite DNAs. Monomers of 144, 148, and 168 bp were identified in MsCR-1, MsCR-2, and MsCR-3, respectively, while 15 and 39 bp monomers were identified in MsCR-4 and MsCR-5, respectively. Three repetitive sequences were characterized as subtelomeric; one repetitive sequence, MsTR-1, had a 184 bp monomer, and two repetitive sequences had fragments of 204 and 327 bp. Sequence analysis revealed homology (70–80 %) between MsTR-1 and a highly repeated sequence (C300) isolated from M. ssp. caerulea. Three identified repetitive sequences produced hybridization signals at multiple sites in a few of the chromosomes; one repetitive sequence was identified as the E180 satellite DNA previously isolated from M. sativa, while the other 163 and 227 bp fragments had distinct sequences. Physical mapping of the repetitive sequences with double-target FISH revealed different patterns. Thus, nine novel tandemly repetitive sequences that can be adopted as distinct chromosome markers in alfalfa were identified in this study. Furthermore, the chromosome distribution of each sequence was well described. Though significant chromosome variations were detected within and between cultivars, a molecular karyotype of alfalfa was suggested with the chromosome markers we identified. Therefore, these novel chromosome markers will still be a powerful tool for genome composition analysis, phylogenetic studies, and breeding applications.     

Alfalfa (Medicago sativa) carbamoylphosphate synthetase gene structure records the deep lineage of plants

Given the central role of carbamoylphosphate synthetases in pyrimidine and arginine metabolism in all living organisms, the absence of fundamental information regarding plant CPSase genes is a striking omission [Lawson et al., Mol. Biol. Evol. 13 (1996) 970-977; van den Hoff et al., J. Mol. Evol. 41 (1995) 813-832]. Whereas CPSase gene architecture and aa sequence have proven to be useful characters in establishing ancient and modern genetic affinities, phylogenetic analysis cannot be completed without the inclusion of plant CPSases. We describe the first isolation by molecular cloning of a plant CPSase gene (CPAII) derived from alfalfa (Medicago sativa). DNA sequence analysis reveals a proteobacterial architecture, namely closely linked carA and carB coding domains separated by a short intergenic region, and transcribed as a polycistronic mRNA. CPAII encodes the amino acid residues that typify a CPSase type II enzyme. In addition, an ancient internal duplication has been retained in the plant carB sequence. Partial nucleotide sequencing of additional clones reveals that the alfalfa genome contains multiple CPSase II gene copies which may be tissue-specific in their expression. It appears that with respect to CPSase genes, CPAII resembles the carAB gene of bacteria, and may have preserved much of this ancient gene structure in the alfalfa genome.     

Somatic hybrid plants between the forage legumes Medicago sativa L. and Medicago arborea L.

Interspecific somatic hybrid plants were obtained by symmetrical electrofusion of mesophyll protoplasts of Medicago sativa with callus protoplasts of Medicago arborea. Somatic hybrid calli were picked manually from semi-solid culture medium after they were identified by their dual color in fluorescent light. Twelve putative hybrid calli were selected and one of them regenerated plants. The morphogenesis of the somatic hybrid calli was induced by the synthetic growth regulator 1,2 benzisoxazole-3-acetic acid. Somatic hybrid plants showed intensive genome rearrangements, as evidenced by isozyme and RFLP analysis. The morphology of somatic hybrid plants was in general intermediate between the parents. The production of hybrids by protoplast fusion between sexually incompatible Medicago species is related to the in vitro respon siveness of the parental protoplasts. The possibility of using somatic hybrid plants in alfalfa breeding is discussed.     

Liming of alfalfa (Medicago sativa L.)

Summary A growth-chamber experiment was conducted to study the effect of liming upon growth of alfalfa. The beneficial effects observed were related to changes in soil properties brought about by lime application. Reductions of aluminum and manganese toxicities were the major factors responsible for the increased yields and the decreased growth period required to reach harvest stage. Significant correlations between plant growth parameters and various measures of extractable aluminum were found.     

Characterization of alfalfa (Medicago sativa L.) plants regenerated from selected NaCl tolerant cell lines

Selection of stable, NaCl tolerant alfalfa (Medicago sativa L.) cell lines was accomplished by a step-up selection procedure, whereby cell lines originally selected for tolerance at 0.5% NaCl were subsequently selected at 1.0% NaCl. Sodium chloride tolerant cell lines retained tolerance following four subcultures (16 weeks) on control media (0% NaCl). Plants were regenerated from selected NaCl tolerant cell lines of three initial genotypes, one diploid (2n=2x=16) and two tetraploids (2n=4x=32). In addition, plants were regenerated from control cell lines maintained on 0% NaCl media for the same duration. Plants regenerated from NaCl tolerant cell lines were characterized by extensive somaclonal variation compared to plants regenerated from control lines. Morphologically, all plants regenerated from NaCl tolerant cell lines are abnormal and many (44.7%) were extreme dwarfs (maximum height of 5 cm). The grossly aberrant phenotypes prevented an in-depth characterization of many of the plants regenerated from NaCl tolerant cell lines. Most plants regenerated from NaCl tolerant cell lines had unbalanced polyploid chromosome sets with the most extreme cytogenetic variant having 106 chromosomes. In contrast, 98.5% of the plants regenerated from control cell lines were euploid (85% were tetraploid, 15% were octoploid). Isozyme phenotypes of the plants from NaCl tolerant cell lines were also extensively altered, compared to plants from control cell lines. In vitro NaCl tolerance was maintained following plant regeneration for nine of the 12 regenerants tested. Importantly, whole plant NaCl tolerance was expressed in two of the seven regenerated plants tested at the whole plant level; however, only one of these plants has flowered and is both male and female sterile; the other plant has never flowered. Although NaCl tolerant alfalfa cell lines are efficiently selected, the extensive somaclonal variation that accompanied the selection was a deterrent to successful recovery of heritable NaCl tolerance.     

Regeneration of foreign genes co-transformed plants of Medicago sativa L by Agrobacterium rhizogenes

Gene encoding sulphur amino acid-rich protein (HNP) and rol genes were transferred into Medicago sativa L (alfalfa) mediated by Agrobacterium tumafeciens. Regeneration of transgenic plants was induced successfully from hairy root tissue of cotyledon in alfalfa. Cotyledon tissues were an ideally transformed recipient. There was a negative correlation between age of hairy roots and embryogenesis frequency in alfalfa. Production of co-transformed plants with greater yield and super quality was important for development of new alfalfa varieties.     

Characterization of salt tolerant alfalfa (Medicago sativa L.) plants regenerated from salt tolerant cell lines

Salt tolerant cell lines have been selected from Medicago sativa, by a single step selection process on tissue culture medium containing 1% NaCl. Plants regenerated from these lines show improved salt tolerance compared to parent plants. The regenerated plants are vigorous, have flowered and are self fertile. The cellular salt tolerance characteristic can be passaged through the regenerated plants, since callus cultures initiated from immature ovaries of the salt tolerant regenerated plants are salt tolerant without additional selection on 1% NaCl. Several of these second generation callus cultures have been regenerated to produce vigorous plants which maintain the salt tolerance characteristic. The tolerance phenotype appears dominant in seeds obtained from self fertilization of the tolerant plants. The regenerated salt tolerant plants are therefore a valuable source as genotypes in plant breeding for salt tolerance and isolation, identification and manipulation of genes which confer salt tolerance in alfalfa.Abbreviations SH Schenk and Hildebrandt medium - 2,4-D 2,4-dichlorophenoxyacetic acid     

Induced androgenesis in alfalfa (Medicago sativa L.)

Summary Anthers of 10 alfalfa (Medicago sativa L.) lines were used as initial material for the production of androgenic haploids. More than 30 variants of nutrient media were tested. Twenty five different treatments with low temperatures and gamma rays were tried in order to find optimal conditions for callus induction and organogenesis.The genotype, stage of microspore development, phytohormonal composition of the nutrient media and pretreatment with physical agents, alone or in combination, affected the efficiency of organogenesis and regeneration in anther cultures of alfalfa.Plants exhibited a high degree of variability in their chromosome number. Haploids, dihaploids and mixoploids were obtained.Cytological studies of in vitro pollen development revealed the origin of the regenerants from microspores.Abbreviations BAP 6-Benzylaminopurine - 2-ip 6-(,-dimethylallylamino)Purine - IAA Indolylacetic Acid - NAA Naphthaleneacetic Acid - 2,4-D Dichlorophenoxyacetic Acid - CMS Cytoplasmic Male Sterility     

Beta-Amylases from Alfalfa (Medicago sativa L.) Roots

Amylase was found in high activity (193 international units per milligram protein) in the tap root of alfalfa (Medicago sativa L. cv. Sonora). The activity was separated by gel filtration chromatography into two fractions with molecular weights of 65,700 (heavy amylase) and 41,700 (light amylase). Activity staining of electrophoretic gels indicated the presence of one isozyme in the heavy amylase fraction and two in the light amylase fraction. Three amylase isozymes with electrophoretic mobilities identical to those in the heavy and the light amylase fractions were the only amylases identified in crude root preparations. Both heavy and light amylases hydrolyzed amylopectin, soluble starch, and amylose but did not hydrolyze pullulan or β-limit dextrin. The ratio of viscosity change to reducing power production during starch hydrolysis was identical for both alfalfa amylase fractions and sweet potato β-amylase, while that of bacterial α-amylase was considerably higher. The identification of maltose and β-limit dextrin as hydrolytic end-products confirmed that these alfalfa root amylases are all β-amylases.     

Transition state analysis of adenosine nucleosidase from yellow lupin (Lupinus luteus)

The transition state of adenosine nucleosidase (EC 3.2.2.7) isolated from yellow lupin (Lupinus luteus) was determined based upon a series of heavy atom kinetic isotope effects. Adenosine labeled with 13C, 2H, and 15N was analyzed by liquid chromatography/electrospray mass spectrometry to determine kinetic isotope effects. Values of 1.024+/-0.004, 1.121+/-0.005, 1.093+/-0.004, 0.993+/-0.006, and 1.028+/-0.005 were found for [1'-13C], [1'-2H], [2'-2H], [5'-2H], and [9-15N] adenosine, respectively. Using a bond order bond energy vibrational analysis, a transition state consisting of a significantly broken C-N bond, formation of an oxocarbenium ion in the ribose ring, a conformation of C3-exo for the ribose ring, and protonation of the heterocyclic base was proposed. This transition state was found to be very similar to the transition state for nucleoside hydrolase, another purine metabolizing enzyme, isolated from Crithidia fasciculata.     

Proteomics of Medicago sativa cell walls

A method for the sequential extraction and profiling by two-dimensional gel electrophoresis (2-DE) of Medicago sativa (alfalfa) stem cell wall proteins is described. Protein extraction included freezing, grinding in a sodium acetate buffer, separation by filtration of cell walls from cytosolic contents, and extensive washing. Cell wall proteins were then extracted sequentially with a solution containing 200 mM CaCl2 and 50 mM sodium acetate, followed by extraction with 3.0 M LiCl and 50 mM sodium acetate. Cell wall proteins from both the CaCl2 and LiCl fractions were profiled by 2-DE. Approximately 150 protein spots were extracted from these two gels, digested with trypsin, and analyzed using nanoscale HPLC coupled to a hybrid quadrupole time-of-flight (Q-tof) tandem mass spectrometer (LC/MS/MS). More than 100 proteins were identified and used in conjunction with the 2-DE profiles to generate proteomic reference maps for cell walls of this important legume. Identified proteins include classical cell wall proteins as well as proteins traditionally considered as non-secreted. Two unique extracellular proteins were also identified.     

Embryogenic response of Mexican alfalfa (Medicago sativa) varieties

The in vitro embryogenic response of nine varieties of alfalfa (Medicago sativa L.) grown in México (five Mexican varieties: Puebla 76, Inia 76, Bajío 76, Sintético I and Sintético II and four foreign or introduced varieties: Moapa 69, San Joaquín II, Hairy Peruvian and Valenciana) were tested. We screened 25 genotypes from each variety in four tissue culture protocols. All the varieties, except San Joaquín II, gave a positive response in one or more of the protocols tested. The response in each variety was low; this was also observed in a wider screening performed with the varieties Moapa 69, Hairy Peruvian, Sintético I and Sintético II. Two plants from Moapa 69 were regenerated and appeared normal.     

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.     

Fine root demography in alfalfa (Medicago sativa L.)

In perennial forages like alfalfa (Medicago sativa L.), repeated herbage removal may alter root production and mortality which, in turn, could affect deposition of fixed N in soil. Our objective was to determine the extent and patterns of fine-diameter root production and loss during the year of alfalfa stand establishment. The experiment was conducted on a loamy sand soil (Udorthentic Haploboroll) in Minnesota, USA, using horizontally installed minirhizotrons placed directly under the seeded rows at 10, 20, and 40 cm depths in four replicate blocks. We seeded four alfalfa germplasms that differed in N₂ fixation capacity and root system architecture: Agate alfalfa, a winter hardy commercially-available cultivar; Ineffective Agate, which is a non-N₂-fixing near isoline of Agate; a new germplasm that has few fibrous roots and strong tap-rooted traits; and a new germplasm that has many fibrous roots and a strongly branched root system architecture. Video images collected biweekly throughout the initial growing season were processed using C-MAP-ROOTS software.More than one-half of all fine roots in the upper 20 cm were produced during the first 7 weeks of growth. Root production was similar among germplasms, except that the highly fibrous, branch-rooted germplasm produced 29% more fine roots at 20 cm than other germplasms. In all germplasms, about 7% of the fine roots at each depth developed into secondarily thickened roots. By the end of the first growing season, greatest fine root mortality had occurred in the uppermost depth (48%), and least occurred at 40 cm (36%). Survival of contemporaneous root cohorts was not related to soil depth in a simple fashion, although all survivorship curves could be described using only five rates of exponential decline. There was a significant reduction in fine root mortality before the first herbage harvest, followed by a pronounced loss (average 22%) of fine roots at the 10- and 20-cm depths in the 2-week period following herbage removal. Median life spans of these early-season cohorts ranged from 58 to 131 days, based on fitted exponential equations. At all depths, fine roots produced in the 4 weeks before harvest (early- to mid-August) tended to have shorter median life spans than early-season cohorts. Similar patterns of fine root mortality did not occur at the second harvest. Germplasms differed in the pattern, but not the ultimate extent, of fine root mortality. Fine root turnover during the first year of alfalfa establishment in this experiment released an estimated 830 kg C ha^–1 and 60 kg N ha^–1, with no differences due to N₂ fixation capacity or root system architecture.     

Cryopreservation of alfalfa (Medicago sativa L.) cells by encapsulation-dehydration

Our objective was to establish a cryopreservation protocol for alfalfa (Medicago sativa L.) cells and study the physiological changes occurring in cells during cryopreservation treatment. Cell cultures of Pioneer cvs. 5262 (fall-dormant, winter-hardy) and 5929 (non-dormant, non-hardy) plants initiated regrowth after cryopreservation by encapsulation-dehydration (ED). Pre-treatment of the encapsulated cells for 4 days in B5 medium containing 0.75 M sucrose and dehydration for 4 h in a laminar flow hood were necessary to achieve maximum cell viability after ED and cryopreservation in liquid N₂ (EDN). Viability (measured as triphenyl tetrazolium chloride reduction) of the cv. 5262 cells after cryopreservation was two- to three-fold greater than that of the cv. 5929 cells. Cold acclimation of the cells (10 days at 2°C) improved viability after cryopreservation. The addition of 7.6 µM ABA to the B5 medium enhanced viability in ED but did not improve cell cryopreservability. Cold-acclimated cells had higher protein concentrations, but neither ABA nor cold acclimation influenced protein composition of cold-acclimated cells determined using SDS-PAGE. Encapsulated cells pre-treated for 4 days in B5 medium containing 0.75 M sucrose showed an increased concentration of cell protein and an altered protein composition. Suspension cultures were re-initiated from both ED and EDN treatments by transferring beads sequentially to B5 media containing 0.75, 0.5, 0.25 M sucrose and then to fresh B5 medium. The ED cells resumed rapid growth after two subcultures, whereas EDN cells needed four or five subcultures to resume rapid growth.     

Purification of beta-amylase from alfalfa (Medicago sativa L.) seeds

An amylase from alfalfa (Medicago sativa L. c.v. Moapa) seeds was purified by column chromatography and gel filtration, followed by chromatofocusing on Mono P HR 5/20. The last step was effective for separation of the alfalfa amylase to a homogeneous state. The purified amylase was identified as beta-amylase from the fact that only beta-maltose was formed by the enzymatic degradation of soluble starch. The molecular weight and specific activity of the beta-amylase (E1%(280 nm) = 18.3) were determined to be 61,000 and 1,077 A.U./mg, respectively. The beta-amylase activity was inhibited by the modification of sulfhydryl groups with p-chloromercuribenzoic acid. The optimum pH and isoelectric point of alfalfa beta-amylase were 7.0 and 4.8, respectively, which were different from other plant beta-amylases.