Richard Thacker

Expression of a GALACTINOL SYNTHASE Gene in Tomato Seeds Is Up-Regulated before Maturation Desiccation and Again after Imbibition whenever Radicle Protrusion Is Prevented

Raffinose family oligosaccharides (RFOs) have been implicated in mitigating the effects of environmental stresses on plants. In seeds, proposed roles for RFOs include protecting cellular integrity during desiccation and/or imbibition, extending longevity in the dehydrated state, and providing substrates for energy generation during germination. A gene encoding galactinol synthase (GOLS), the first committed enzyme in the biosynthesis of RFOs, was cloned from tomato (Lycopersicon esculentum Mill. cv Moneymaker) seeds, and its expression was characterized in tomato seeds and seedlings. GOLS (LeGOLS-1) mRNA accumulated in developing tomato seeds concomitant with maximum dry weight deposition and the acquisition of desiccation tolerance.LeGOLS-1 mRNA was present in mature, desiccated seeds but declined within 8 h of imbibition in wild-type seeds. However, LeGOLS-1 mRNA accumulated again in imbibed seeds prevented from completing germination by dormancy or water deficit. Gibberellin-deficient (gib-1) seeds maintainedLeGOLS-1 mRNA amounts after imbibition unless supplied with gibberellin, whereas abscisic acid (ABA) did not prevent the loss of LeGOLS-1 mRNA from wild-type seeds. The presence of LeGOLS-1mRNA in ABA-deficient (sitiens) tomato seeds indicated that wild-type amounts of ABA are not necessary for its accumulation during seed development. In all cases,LeGOLS-1 mRNA was most prevalent in the radicle tip. LeGOLS-1 mRNA accumulation was induced by dehydration but not by cold in germinating seeds, whereas both stresses induced LeGOLS-1mRNA accumulation in seedling leaves. The physiological implications ofLeGOLS-1 expression patterns in seeds and leaves are discussed in light of the hypothesized role of RFOs in plant stress tolerance.

2,3-Dihydrofarnesoic acid, a unique terpene from trichomes ofLycopersicon hirsutum, repels spider mites

Lycopersicon hirsutum, a wild relative of the tomato, is highly resistant to arthropod herbivores. Both botanic forms ofL. hirsutum, L. hirsutum f.glabratum (C.H. Mull.) andL. hirsutum f.typicum (Humb. & Bonpl.), are resistant to two-spotted spider mites,Tetranychus urticae Koch. However, leaves and trichome secretions from f.typicum repel mites more so than those from f.glabratum. We have previously demonstrated that trichome secretions from LA 1363 and LA 1927, accessions of f.typicum, repelled mites. In this paper we report the identification of the primary component of trichome secretions responsible for repellency. Leaflet washes having compositions similar to trichome secretions were collected and separated into neutral and acid fractions; repellency was mainly associated with the acid fraction, which, when applied to nonrepellent leaflets of f.glabratum, rendered them repellent. Separation of leaflet washes by HPLC allowed purification and subsequent identification by gas chromatography-mass spectrometry and nuclear magnetic resonance of 2,3-dihydrofamesoic acid (3,7,11-trimethyl-6, 10-dodecadienoic acid) as the primary chemical component responsible for repellency. Application of this acid to leaflets ofL. esculentum rendered them repellent. Other volatile compounds present in minor amounts in the acid fractions were farnesoic acid and 16∶0, 16∶3, 18∶0, 18∶2, and 18∶3 fatty acids. This is the first report of the natural occurrence of 2,3-dihydrofarnesoic acid.

Attractancy and Ovipositional Response of Adult Bemisia argentifolii (Homoptera: Aleyrodidae) to Type IV Trichome Density on Leaves of Lycopersicon hirsutum Grown in Three Day-Length Regimes

Clonal plants of six accessions of Lycopersicon hirsutum Humb. and Bonpl., a wild relative of tomato, were grown in three day-length regimes. Clones of an accession grown in different day-length re...

Communication between the Maternal Testa and the Embryo and/or Endosperm Affect Testa Attributes in Tomato

Two tomato (Lycopersicon esculentum) mutants with dark testae displaying poor germination rate and percentage on both water and 100 μm gibberellin4 + 7 were recovered. The mutants were allelic (black seed1-1; bks1-1 and bks1-2), inherited in Mendelian fashion as a recessive gene residing on chromosome 11. They are not allelic to bs (brown seed) -1, -2, or -4, which impair seed germination and possess dark testae. The bks/bs mutants accumulated dark pigment in the cell layers of the testa above the endothelium, which itself accumulated proanthocyanidins similar to wild type. The poor germination performance of bks mutant seeds was because of impediment of the mutant testae to radicle egress. Imbibition on gibberellin4 + 7 did not ameliorate germination percentage or rate. The toughening of the bks testa and associated poor germination were partially overcome when seeds were not dried before germination or were dried under N2. The seeds of the bks mutant have elevated activity of at least one enzyme responsible for the detoxification of reactive oxygen species. The bks mutant is epistatic to 12 anthocyaninless mutants of tomato. Bio- and physicochemical analysis of the bks testa determined that it accumulated a melanic substance. Inheritance of bks/bs mutations contrasts with that of the anthocyaninless mutants, which are inherited according to the genotype of the maternally derived testa. This suggests that the testa manufactures components before its demise that can maximize testa strength, whereas the endosperm/embryo produces factors that are conveyed to the testa, mitigating this process.

An increase in glutathione peroxidase activity induced by high supplementation of vitamin C in rats

Abstract Weanling rats were maintained on purified diets containing marginal levels of vitamin E; they were divided into three groups with six rats each, and received vitamin C at 0, 2.0, or 4.0 g/kg diet for 16 weeks. The determination of antioxidant status of the animals showed that the high supplementation of vitamin C significantly lowered plasma level of vitamin E and erythrocyte (RBC) level of reduced glutathione. The activity of glutathione peroxidase increased significantly in RBC and plasma; but not in the liver, kidney, spleen, muscle, heart, and testis of the vitamin C supplemented groups. The activities of superoxide dismutase, catalase, glutathione reductase and glucose-6-phosphate dehydrogenase in RBC and liver were not affected by the vitamin C supplementation. The increase in glutathione peroxidase activity in RBC of high vitamin C supplemented groups may be due to the development of cellular defense mechanisms induced by peroxidative stress of vitamin C.

Occurrence of 2,3-dihydrofarnesoic acid, a spidermite repellent, in trichome secretions of Lycopersicon esculentum × L. hirsutum hybrids

The sesquiterpenoid spidermite repellent, 2,3-dihydrofarnesoic acid, occurs in trichome secretions of LA1363, an accession of the wild tomato Lycopersicon hirsutum. To better understand the inheritance of this sesquiterpene acid and its relationship with the quantity trichome secretions, interspecific crosses were made with five inbred lines of L. esculentum. Limited seed set and frequent seedling mortality led to small populations for each generation. Concentrations of residues in leaflet washes, comprised of trichome secretions and concentrations of 2,3-dihydrofarnsoic acids were determined in F1, F2 and backcross generations. Low concentrations of this acid occurred in F1 hybrids, suggesting there was dominance for low levels of the acid. However, concentrations of 2,3-dihydrofarnesoic acid were below minimum levels of detection in two backcross generations and in one of two F2 generations. Concentrations of leaflet wash residues were high on the L. hirsutum parent and low on the L. esculentum parents. Concentrations on hybrids were generally intermediate. However, high residue concentrations were present on a few F1 and F2 hybrids, Residue and 2,3-dihydrofarnesoic acid concentrations were not correlated in F1 or in backcross generations and were uncorrelated in one of two F2 generations. In the F2 obtained by sib-mating, residue concentrations were correlated with 2,3-dihydrofarnesoic acid concentrations. Although small population sizes and perhaps other factors did not allow delineation of genetic control of the presence or abundance of 2,3-dihydrofarnesoic acid, interspecific hybrids that produce 2,3-dihydrofarnesoic acid provide the experimental plants essential for research designed to provide a better understanding of the role of 2,3-dihydrofarnesoic acid in host-plant resistance of tomato to mites and insects.

Effects of dietary vitamin E and high supplementation of vitamin C on plasma glucose and cholesterol levels

Abstract Weanling male Sprague Dawley rats were fed ad libitum a purified basal diet free of vitamins E and C. In Experiment I (4 weeks), 24 rats were divided into four groups with 2×2 factorial design. They were supplemented with 0 or 45 IU/kg diet of vitamin E, and O or 2.0 g/kg diet of vitamin C. In Experiment II (16 weeks), 36 rats were divided into six groups with 2×3 factorial design. Vitamin E was supplemented at the level of O or 45 IU/kg diet, and vitamin C was supplemented at the level of O, 1.5, or 3.0 g/kg diet, respectively. Plasma glucose level and cholesterol level were determined in both experiments. The plasma levels of glucose and cholesterol were significantly and negatively correlated. Plasma glucose level was significantly increased and plasma cholesterol level significantly decreased by the high supplementation of vitamin C with or without vitamin E in the diet. Vitamin E deficiency decreased plasma glucose level and increased plasma cholesterol level significantly with or without vitamin C supplementation. The groups with adequate level of vitamin E (45 IU/kg diet) and no vitamin C showed moderate plasma glucose and cholesterol levels.

Thinking Outside the Asclepias Box: Oleander Aphids and Honeyvine Milkweed

ABSTRACT The oleander aphid, Aphis nerii Boyer de Fonscolombe, feeds on milkweeds in the Apocynaceae family. In Kentucky, A. nerii colonizes several common Asclepias species and honeyvine milkweed, Cynanchum laeve (Michaux). Previous studies investigating whether and how host plant characteristics influence A. nerii fitness have produced conflicting results. Our observations suggested that A. nerii more readily colonized C. laeve than Asclepias species. We hypothesized that aphid fitness differed among host plant species having different characteristics, and specifically, that A. nerii performance would be greatest on host plants having low cardenolide concentrations and few physical defenses. Physical and chemical characteristics were measured on C. laeve and three Asclepias species. Laboratory and field experiments were conducted to compare A. nerii performance among these four milkweed species in the absence of natural enemies. Changes in aphid densities over time were examined in the presence of natural enemies. Plant characteristics and aphid performance were found to differ among milkweed species. In the absence of natural enemies, A. nerii performance was best on C. laeve. When exposed to natural enemies, A. nerii densities remained higher on A. incarnata and C. laeve than on A. syriaca and A. tuberosa. Physical differences between C. laeve, a vining milkweed, and tested Asclepias species may increase suitability of honeyvine milkweed for A. nerii colonization. Our results suggest that C. laeve may rely more on tolerance and less on nonpreference or antibiosis resistance to herbivores.

Relative biopotency of vitamin E compounds as determined by reversal of plasma pyruvate kinase activity in curative myopathy of rats

Abstract The biopotency of four vitamin E compounds relative to all - rac -α-tocopheryl acetate was determined using plasma pyruvate kinase activity as an index of myopathy. The results showed that the relative potency of RRR-α-tocopheryl acetate was 1.31, that of 2-ambo-α-tocopheryl acetate was 1.09, that of RRR-α-tocopherol was 1.45, and that of d-γ-tocopherol was 0.21 to 0.24. The bioassay based on the recovery of plasma pyruvate kinase activity was proven to be a convenient and reliable bioassay method for vitamin E compounds.

Plasma lactic dehydrogenase electrophoretic patterns of long-term vitamin E-deficient rats

Abstract Weanling male Sprague Dawley rats were fed a vitamin E-deficient basal diet with or without supplementation of 100 IU vitamin E per kg. diet for 12 months. Plasma total activity of lactic dehydrogenase (LDH) was significantly higher in the vitamin E-deficient group than the control group. Isoenzymes of LDH in plasma were separated by electrophoresis, and quantitated. The results showed the presence of five isozymes (LDH 1 — LHD 5 ) in the vitamin E-deficient plasma as compared with three isozymes (LDH 1 , LDH 4 and LDH 5 ) in the control plasma. The LDH 1 , LDH 4 and LDH 5 isozymes were significantly elevated in the vitamin E-deficient group when compared with the control group. The LDH 2 and LDH 3 isozymes, which were not observed in the electrophorogram of the control plasma, appeared in the electrophorogram of vitamin E-deficient plasma. The electrophorogram of LDH isozymes, combined with the results of a previous tissue enzymatic and histopathological study, suggests the tissue sources of LDH leakage into the blood in vitamin E deficiency are mainly heart (LDH 1 , LDH 2 , and LDH 3 ) and skeletal muscle (LDH 4 and LDH 5 ).