Sequential enzymes of linoleic acid oxidation in corn germ: lipoxygenase and linoleate hydroperoxide isomerase

Linoleic acid oxidation catalyzed by lipoxygenase (lipoxidase) activity in extracts of defatted corn germ does not terminate in the product, linoleic acid hydroperoxide, unless the lipoxygenase is first partially purified. If purification is not attempted, the hydroperoxide product exists only as a barely detectable intermediate in the synthesis of three products. One of these was identified as 9-hydroxy-10-oxo-cis-12-octadecenoic acid formed from the hydroperoxide by the enzyme, linoleate hydroperoxide isomerase. Another product, 13-hydroxy-10-oxo-trans-11-octadecenoic acid, is believed to be formed by an isomerase also. The third product was the linoleate ester of one of the hydroxy-oxo-fatty acids, 9-(cis-9,cis-12-octadecadienoyl)-10-oxo-cis-12-octadecenoic acid. It is not known if the synthesis of the ester is enzyme-catalyzed. When a mixture of 13-hydroperoxy-cis-9,trans-11-octa-decadienoic acid and 9-hydroperoxy-trans-10,cis-12-octa-decadienoic acid from soybean lipoxygenase oxidation of linoleic acid was used as a substrate, 13-hydroxy-12-oxo-cis-9-octadecenoic acid and 9-hydroxy-12-oxo-trans-10-octadecenoic acid were formed as the major products of catalysis by linoleate hydroperoxide isomerase(s) from corn. Smaller quantities of 9-hydroxy-10-oxo-cis-12-octadecenoic acid and 13-hydroxy-10-oxo-trans-11-octadecenoic acid were also formed.     

Isolation and characterization of phytotoxic compounds produced by Phomopsis helianthi

The isolation, chemical characterization and biological activity of two phytotoxic metabolites of Phomopsis helianthi Munt-Cvet et al. is reported. These compounds were identified by spectroscopic methods (UV, IR, 1H and 13C NMR, and MS) as trans-4,6-dihydroxymellein (trans-3-methyl-4,6,8-trihydroxy-3,4-dihyroisocoumarin) and cis-4,6-dihydroxymellein (cis-3-methyl-4,6,8-trihydroxy-3,4-dihydroisocoumarin). This is the first report of the isolation of trans-4,6-dihydroxymellein from fungal cultures and of the production of cis- and trans-4,6-dihydroxymelleins by P. helianthi. Rice was found to be a good substrate for the production of the dihydroxymelleins. Culture extracts of some Italian and French strains of P. helianthi showed different degrees of phytotoxicity towards sunflower leaves and seedlings. The minimum effective doses of trans- and cis-4,6-dihydroxymelleins with different bioassays were 76 and 135 microg per spot (leaf puncture bioassay), 3 and 5 micromol g(-1) fresh tissue (absorption by leaf cutting) and 5 and 2 micromol g(-1) fresh tissue (absorption by cut seedlings), respectively. These compounds may contribute to the severity of the sunflower disease caused by P. helianthi.     

Triterpenes from Periandra dulcis roots

Three oleanane triterpenes were isolated from the roots of Periandra dulcis,and identified as 3β-hydroxy-25-al-olean-18-en-30-oic acid (periandric acid I), 3β-hydroxy-25-al-olean-12-en-30-oic acid (periandric acid II) and 3-oxo-25-hydroxy-olean-12-en-30-oic acid. The former two compounds (periandric acids I and II) were identical with the aglycones obtained by hydrolysis of periandrin I and II, respectively and the latter one was a new triterpene.     

Peroxygenase-Catalyzed Fatty Acid Epoxidation in Cereal Seeds (Sequential Oxidation of Linoleic Acid into 9(S),12(S),13(S)-Trihydroxy-10(E)-Octadecenoic Acid)

Peroxygenase-catalyzed epoxidation of oleic acid in preparations of cereal seeds was investigated. The 105,000g particle fraction of oat (Avena sativa) seed homogenate showed high peroxygenase activity, i.e. 3034 [plus or minus] 288 and 2441 [plus or minus] 168 nmol (10 min)-1 mg-1 protein in two cultivars, whereas the corresponding fraction obtained from barley (Hordeum vulgare and Hordeum distichum), rye (Secale cereale), and wheat (Triticum aestivum) showed only weak activity, i.e. 13 to 138 nmol (10 min)-1 mg-1 protein. In subcellular fractions of oat seed homogenate, peroxygenase specific activity was highest in the 105,000g particle fraction, whereas lipoxygenase activity was more evenly distributed and highest in the 105,000g supernatant fraction. Incubation of [1-14C]linoleic acid with the 105,000g supernatant of oat seed homogenate led to the formation of several metabolites, i.e. in order of decreasing abundance, 9(S)-hydroxy-10(E),12(Z)-octadecadienoic acid, 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid, cis-9,10-epoxy-12(Z)-octadecenoic acid [mainly the 9(R),10(S) enantiomer], cis-12,13-epoxy-9(Z)-octadecenoic acid [mainly the 12(R),13(S) enantiomer], threo-12,13-dihydroxy-9(Z)-octadecenoic acid, and 12(R),13(S)-epoxy-9(S)-hydroxy-10(E)-octadecenoic acid. Incubation of linoleic acid with the 105,000g particle fraction gave a similar, but not identical, pattern of metabolites. Conversion of linoleic acid into 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid, a naturally occurring oxylipin with antifungal properties, took place by a pathway involving sequential catalysis by lipoxygenase, peroxygenase, and epoxide hydrolase.     

Metabolism of linoleic acid by human gut bacteria: different routes for biosynthesis of conjugated linoleic acid

A survey of 30 representative strains of human gram-positive intestinal bacteria indicated that Roseburia species were among the most active in metabolizing linoleic acid (cis-9,cis-12-18:2). Different Roseburia spp. formed either vaccenic acid (trans-11-18:1) or a 10-hydroxy-18:1; these compounds are precursors of the health-promoting conjugated linoleic acid cis-9,trans-11-18:2 in human tissues and the intestine, respectively.     

Bt玉米秸秆还田对小麦幼苗生长发育的影响

以已进入中间试验阶段的Bt玉米及其亲本(非Bt玉米)秸秆为材料,与营养土及蛭石混合后培养小麦幼苗,同时以未使用秸秆的相应土为空白对照,在室内条件下研究了Bt玉米与亲本秸秆还田对后茬小麦的影响。结果表明:(1)不同秸秆还田对小麦幼苗出苗率、株高没有显著影响;(2)非转基因玉米与转Bt玉米秸秆拌土后地上部鲜重仅为对照鲜重的51%和65%,干重仅为对照的62%和72%,均达到差异显著水平;(3)Bt玉米秸秆还田降低小麦幼苗生长素(IAA)含量,郑58秸秆拌土增加了幼苗脱落酸(ABA)含量;(4)两种处理均提高了幼苗的超氧化物歧化酶(SOD)总活性。因此,秸秆拌土对小麦幼苗的处理效应一致,与秸秆类型无关,该研究可为评价转Bt玉米环境安全提供一定的理论依据。     

Allelopathic effects of sunflower extracts on mustard seed germination and seedling growth

The allelopathic potential of two cultivars of sunflower (Helianthus annuus L.) Lech and Ogrodowy was studied. Leaf aqueous extracts of sunflower at 2.5, 5, and 10 % (m/v) concentrations were applied to determine their effect on mustard (Sinapis alba) seed germination and seedlings growth under laboratory conditions. Increasing concentration of aqueous extracts of sunflower inhibited seed germination, up to almost complete failure of germination, observed in the presence of 10 % extract from sunflower cv. Ogrodowy. The decrease in germinability was well correlated with increased membrane deterioration, assayed as electrical conductivity and enhanced lipid peroxidation, detected as increased malondialdehyde content.     

Physiological Studies of a Synthetic Gibberellin-Like Bioregulator: II. Effect of Site of Application on Biological Activity

The biological activity of the synthetic gibberellin agonist AC-94,377 (1-[3-chlorophthalimido]-cyclohexanecarboxamide) in certain plants is strictly dependent on the site of application. Root application of AC-94,377 at concentrations greater than or equal to 1 micromolar to seedlings of dwarf corn (Zea mays L. var d₅), dwarf rice (Oryza sativa L. cv Tan-ginbozu), and sunflower (Helianthus annuus L. cv NK265) seedlings resulted in readily measurable gibberellin-like biological activity. Application of up to 10 micrograms of AC-94,377 to the shoots of these same species had no effect. AC-94,377 was metabolized to more polar products in both dwarf corn and sunflower seedlings. After 4 days of continuous root treatment with [¹⁴C]AC-94,377, greater than 70% of the recovered ¹⁴C was found in the form of unmetabolized AC-94,377. In contrast, only 30 to 40% of the recovered ¹⁴C was unmetabolized 4 days after shoot treatment. Translocation studies demonstrated that the movement of [¹⁴C]AC-94,377 was limited and occurred almost exclusively in an apoplastic fashion. Four days after leaf treatment, less than 1.5% (corn) or 4% (sunflower) of the recovered radioactivity had moved away from the treated area. It was concluded that the lack of biological activity of AC-94,377 following shoot treatment resulted principally from limited phloem mobility and to a lesser extent from accelerated metabolic breakdown.     

Manganese-induced salt stress tolerance in rice seedlings: regulation of ion homeostasis,antioxidant defense and glyoxalase systems

Hydroponically grown 12-day-old rice (Oryza sativa L. cv. BRRI dhan47) seedlings were exposed to 150 mM NaCl alone and combined with 0.5 mM MnSO₄. Salt stress resulted in disruption of ion homeostasis by Na⁺ influx and K⁺ efflux. Higher accumulation of Na⁺ and water imbalance under salinity caused osmotic stress, chlorosis, and growth inhibition. Salt-induced ionic toxicity and osmotic stress consequently resulted in oxidative stress by disrupting the antioxidant defense and glyoxalase systems through overproduction of reactive oxygen species (ROS) and methylglyoxal (MG), respectively. The salt-induced damage increased with the increasing duration of stress. However, exogenous application of manganese (Mn) helped the plants to partially recover from the inhibited growth and chlorosis by improving ionic and osmotic homeostasis through decreasing Na⁺ influx and increasing water status, respectively. Exogenous application of Mn increased ROS detoxification by increasing the content of the phenolic compounds, flavonoids, and ascorbate (AsA), and increasing the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), superoxide dismutase (SOD), and catalase (CAT) in the salt-treated seedlings. Supplemental Mn also reinforced MG detoxification by increasing the activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) in the salt-affected seedlings. Thus, exogenous application of Mn conferred salt-stress tolerance through the coordinated action of ion homeostasis and the antioxidant defense and glyoxalase systems in the salt-affected seedlings.     

油菜对3种作物种子萌发和幼苗生长的化感作用

油菜是我国重要的绿肥作物,除增加土壤肥力外,对后茬作物也有一定的化感作用。本文研究了不同浓度油菜浸提液(0.025、0.05和0.1 g·mL^-1)对3种作物(燕麦、玉米和向日葵)种子萌发、幼苗生长及生理生化的影响。结果表明: 油菜浸提液对3种作物种子发芽率的影响不显著,但对燕麦有“低促高抑”的趋势,对向日葵有抑制的趋势。油菜浸提液高浓度处理对燕麦幼苗根和茎长、玉米幼苗茎长以及向日葵幼苗根长起抑制作用,低浓度处理对玉米幼苗根茎长起促进作用。燕麦和向日葵幼苗在浸提液浓度为0.05 g·mL^-1时蛋白质含量最大,玉米在0.025 g·mL^-1时蛋白质含量最大,显著高于对照。3个浓度下,向日葵脯氨酸含量均显著降低,玉米脯氨酸含量在浓度为0.05 g·mL^-1时显著高于对照。玉米过氧化物酶(POD)活性在浸提液浓度为0.05 g·mL^-1时最大,向日葵POD活性在浓度为0.025 g·mL^-1时最大,与对照有显著差异,其余浓度处理与对照无显著差异。油菜浸提液浓度为0.025 g·mL^-1时显著降低了燕麦超氧化物歧化酶(SOD)活性,3种作物幼苗过氧化氢酶(CAT)活性与对照均无显著差异。加入油菜浸提液后,向日葵幼苗丙二醛(MDA)含量在浓度为0.1 g·mL^-1时显著增加,玉米幼苗MDA含量在不同浓度处理下均显著低于对照。综合分析,油菜浸提液对向日葵的化感抑制作用最强,其次为玉米、燕麦。     

Growth promotion and an increase in cell wall extensibility by silicon in rice and some other Poaceae seedlings

The effect of silicon on organ growth and its mechanisms of action were studied in rice ( Oryza sativa L. cv. Koshihikari), oat ( Avena sativa L. cv. Victory), and wheat ( Triticum aestivum L. cv. Daichino-Minori) seedlings grown in the dark. Applying silicon in the form of silicic acid to these seedlings via culture solution resulted in growth promotion of third (rice) or second (oat and wheat) leaves. The optimal concentration of silicon was 5-10 mM. No growth promotion was observed in early organs, such as coleoptiles or first leaves. In silicon-treated rice third leaves, the epidermal cell length increased, especially in the basal regions, without any effect on the number of cells, showing that silicon promoted cell elongation but not cell division. Silicon also increased the cell wall extensibility significantly in the basal regions of rice third leaves. These results indicate that silicon stimulates growth of rice and some other Poaceae leaves by increasing cell wall extensibility.     

Phosphatase activity in corn and soybean roots: Conditions for assay and effects of metals

Studies with sterile root materials showed that the optimum pH values of phosphatase activity in three varieties of each of corn (Zea mays L.) and soybean (Glycine max. L.) were 4 and 5, respectively. The activity on either side of the optimum pH fell sharply, and there was no activity at pH 9. Thus, these roots contain acid but no alkaline phosphatase activity. Acid phosphatase activity was not uniformly distributed in roots and root hairs. Studies with 20 metals showed that their effectiveness in inhibiting acid phosphatase activity of roots varied with the type of plant used. When the metals were compared at 250 μM (1.25 μmole. 5 mg⁻¹ of homogenized roots), the inhibition of acid phosphatase of corn and soybean roots showed that Ag(I), Fe(III), Se(IV), V(IV), As(V) and Mo(VI) were the most effective inhibitors of this enzyme in corn roots, with percentage inhibition ≥30%. In addition to these metals, Sn(II), Hg(II), and W(VI) inhibited acid phosphatase in soybean roots by >30%. Other metals and one non-metallic element that inhibited acid phosphatase activity in corn and soybean roots were: Cu(I), Cu(II), Cd(II), Ni(II), Fe(II), Pb(II), Ba(II), Co(II), Mn(II), Zn(II), B(III), As(III), Cr(III), and Al(III); their degrees of effectiveness varied with type of roots used. Generally, the inhibitory effect of the metals was much less when their concentration was decreased by 10-fold. In addition to the effect of these elements, phosphate ion inhibited acid phosphatase activity of corn and soybean roots. Related anions such as NO ₂ ⁻ , NO ₃ ⁻ , Cl⁻, and SO ₄ ²⁻ were not inhibitory.     

(10E,12Z,15Z)-9-hydroxy-10,12,15-octadecatrienoic acid methyl ester as an anti-inflammatory compound from Ehretia dicksonii

The methanol extract of Ehretia dicksonii provided (10E, 12Z, 15Z)-9-hydroxy-10,12,15-octadecatrienoic acid methyl ester (1) which was isolated as an anti-inflammatory compound. Compound 1 suppressed 12-Otetradecanoyl-phorbol-13-acetate (TPA)-induced inflammation on mouse ears at a dose of 500 microg (the inhibitory effect (IE) was 43%). Linolenic acid methyl ester did not inhibit this inflammation at the same dose. However, the related compounds of 1, (9Z,11E)-13hydroxy-9,11-octadecadienoic acid (5) and (9Z,llE)13-oxo-9,11-octadecadienoic acid (6), showed potent activity (IE500 microg of 63% and 79%, respectively). Compounds 1, 4 ((9Z, 12Z, 14E)-16-hydroxy-9,12,14-octadecatrienoic acid), 5 and 6 also showed inhibitory activity toward soybean lipoxygenase at a concentration of 10 microg/ml.     

Inhibitory effect of sulfur-containing compounds in Scorodocarpus borneensis Becc. on the aggregation of rabbit platelets

The inhibitory effects of three pure compounds isolated from wood garlic, 2,4,5-trithiahexane (I), 2,4,5,7-tetrathiaoctane (II), and 2,4,5,7-tetrathiaoctane 2,2-dioxide (III), on rabbit platelet aggregation induced by collagen, arachidonic acid, U46619, ADP (adenosine 5'-diphosphate), PAF (platelet aggregating factor), and thrombin were studied in vitro. The anti-aggregating activity of 2,4,5,7-tetrathiaoctane 4,4-dioxide (IV) was also measured with collagen and arachidonic acid. I, II, III, and IV inhibited the platelet aggregation induced by all tested agonists. I, II, and III exhibited a stronger inhibitory effect against the thrombin-induced aggregation of GFP (gel-filtered platelets) than against the aggregation induced by the other agonists. Notably, the IC50 value for III was 4 microM, which is approximately 2.5 times stronger than MATS (methyl allyl trisulfide), a major anti-platelet compound isolated from garlic. In inhibiting collagen-induced aggregation, II was as potent as MATS and aspirin, with a marked disaggregation effect on the secondary aggregation by arachidonic acid, at the rate of 47.05%/min at a concentration of 10(-4) M. I, II, and III also suppressed U46619-induced aggregation. These results suggest that sulfur-containing compounds in wood garlic not only inhibit arachidonic acid metabolism but also suppress aggregation in association with the function of the platelet plasma membrane.     

Induction of iron(III) and copper(II) reduction in pea (Pisum sativum L.) roots by Fe and Cu status: Does the root-cell plasmalemma Fe(III)-chelate reductase perform a general role in regulating cation uptake?

We investigated the effects of Fe and Cu status of pea (Pisum sativum L.) seedlings on the regulation of the putative root plasma-membrane Fe(III)-chelate reductase that is involved in Fe(III)-chelate reduction and Fe²⁺ absorption in dicotyledons and nongraminaceous monocotyledons. Additionally, we investigated the ability of this reductase system to reduce Cu(II)-chelates as well as Fe(III)-chelates. Pea seedlings were grown in full nutrient solutions under control, -Fe, and -Cu conditions for up to 18 d. Iron(III) and Cu(II) reductase activity was visualized by placing roots in an agarose gel containing either Fe(III)-EDTA and the Fe(II) chelate, Na₂bathophenanthrolinedisulfonic acid (BPDS), for Fe(III) reduction, or CuSO₄, Na₃citrate, and Na₂-2,9-dimethyl-4,7-diphenyl-1, 10-phenanthrolinedisulfonic acid (BCDS) for Cu(II) reduction. Rates of root Fe(III) and Cu(II) reduction were determined via spectrophotometric assay of the Fe(II)-BPDS or the Cu(I)-BCDS chromophore. Reductase activity was induced or stimulated by either Fe deficiency or Cu depletion of the seedlings. Roots from both Fe-deficient and Cu-depleted plants were able to reduce exogenous Cu(II)-chelate as well as Fe(III)-chelate. When this reductase was induced by Fe deficiency, the accumulation of a number of mineral cations (i.e., Cu, Mn, Fe, Mg, and K) in leaves of pea seedlings was significantly increased. We suggest that, in addition to playing a critical role in Fe absorption, this plasma-membrane reductase system also plays a more general role in the regulation of cation absorption by root cells, possibly via the reduction of critical sulfhydryl groups in transport proteins involved in divalent-cation transport (divalent-cation channels?) across the root-cell plasmalemma.     

Lignin degradation byPhanerochaete chrysosporium: Metabolism of a phenolic phenylcoumaran substructure model compound

The degradation of a lignin substructure model compound, 5-formyl-3-hydroxymethyl-2-(4-hydroxy-3,5-dimethoxyphenyl)-7-methoxycoumaran (I), in ligninolytic culture of a white-rot wood decay fungus,Phanerochaete chrysosporium, was investigated. It was found that I was hydroxylated or dehydrogenated in its coumaran ring to give 2-(5-formyl-2-hydroxy-3-methoxyphenyl)-3-hydroxypropiosyringone (II) and two coumarones, 5-formyl-3-hydroxymethyl-2-(4-hydroxy-3,5-dimethyoxyphenyl)-7-methoxycoumarone (V) and 3,5-diformyl-2-(4-hydroxy-3,5-dimethoxyphenyl)-7-methoxycoumarone (VI), II was further converted to 2,6-dimethoxy-p-benzoquinone (IV), syringic acid (III), and 5-carboxyvanillic acid (VIII). These metabolic products were identified by mass spectrometric comparison with the authentic compounds. A proposed pathway for the degradation of I is presented on the basis of these metabolic products. The degradation could be catalyzed mainly by phenol-oxidizing enzymes.Non-Standard Abbreviations TLC thin layer chromatography     

Transformation of a monoterpene ketone, piperitenone, and related terpenoids using Mucor piriformis

Biotransformation of piperitenone (I), 5,5-dimethyl-2-(1-methylethylidene)-cyclohexanone (II), and 2-(1-ethyl-1-propylidene)-5-methylcyclohexanone (III) was studied using a versatile fungal strain, Mucor piriformis. The organism initiates transformation of these compounds by hydroxylation at the allylic positions or at the tertiary carbon. Transformation of piperitenone (I) by this strain yielded 5-hydroxypiperitenone (Ic), 7-hydroxypiperitenone (Id), 7-hydroxypulegone (Ie), 10-hydroxypiperitenone (If), and 4-hydroxypiperitenone (Ig) as metabolites. It was possible to block some of the metabolic activities of the organism through structural modification of piperitenone (I). This was evidenced by the fact that biotransformation of 5,5-dimethyl-2-(1-methylethylidene)-cyclohexanone (II) yielded 5,5-dimethyl-2-(1-hydroxy-1-methylethyl)-2-cyclohexen-1-one (IIb) and 5,5-dimethyl-3-hydroxy-2-(1-methylethylidene)-cyclohexanone (IIa), whereas 2-(1-ethyl-1-propylidene)-5-methylcyclohexanone (III) yielded 6-(1-ethyl-1-propylidene)-5-methyl-2-cyclohexen-1-one (IIIb) and 6-(1-ethyl-1-propylidene)-5-hydroxy-5-methylcyclohexanone (IIIa) as metabolites. Based on the identification of the metabolites, pathways for the biotransformation of I, II, and III have been proposed. The mode of biotransformation of these compounds by M. piriformis also compared to their modes of metabolism in the rat system.     

三个新2,2—二甲基苯并二氢吡喃类化合物的分离与鉴定

从中药三叉苦(Evodia lepta(Spreng.)Merr.)的地上部分分离鉴定了4个化合物。通过光谱解析和结构沟通的方法确定了它们的结构。其中3个为新化合物,依次命名为leptin A(Ⅰ)、leptin B(Ⅱ)和leptin C(Ⅲ)。另外一个已知化合物为异吴茱萸酮酚(Ⅳ)。     

Uptake and phytotoxicity of the herbicide metsulfuron methyl in corn root tissue in the presence of the safener 1,8-naphthalic anhydride

Growth of Zea mays L. cv Potro roots was inhibited by the herbicide metsulfuron methyl (MSM) at the lowest concentration tested: 5 nanomoles per liter. Pretreatment of corn seeds with commercial 1,8-naphthalic anhydride (NA) at 1% (w/w) partially reversed MSM-induced root growth inhibition. MSM at a concentration of 52 nanomoles per liter was taken up rapidly by roots and accumulated in the corn tissue to concentrations three times those in the external medium; the safener NA increased MSM uptake up to 48 hours. The protective effect of NA was related to the ability of the safener to increase the metabolism of MSM; tenfold increases in the metabolic rates of MSM were observed in NA-pretreated corn seedlings grown for 48 hours on 52 nanomolar [¹⁴C]MSM solution. DNA synthesis determined by measurement of [³H]thymidine incorporation into DNA was inhibited by root MSM applications; after a 6-hour application period, 13 nanomolar MSM solution reduced DNA synthesis by 64%, and the same reduction was also observed with NA-pretreated seedlings. Pretreatment of corn seeds with safener NA did not increase the acetolactate synthase activity in the roots and did not change, up to 13 micromoles per liter, the in vitro sensitivity of roots to MSM.     

Quick Identification of the Members of the Glutamine Synthetase Gene Family from Sunflower by Simultaneous Amplification of cDNA with Degenerate Primers

A single degenerate glutamine synthetase (GS)-specific primer was used to amplify the 3′ end of cDNAs derived from different GS genes that are expressed in leaves and roots of sunflower (Helianthus annuus L. cv. Peredovic). Four types of GS cDNA (I, II, III and IV) were simultaneously amplified from leaves and five types (I, II, V, VI, VII) from roots with a minimum investment of time and experimental work. cDNAs II, III and IV encode chloroplastic isoforms as deduced by the presence of chloroplastic GS-specific features in their sequences. The rest of cDNAs codifies cytosolic isoforms. Using cDNA-specific probes and primers, homologous sequences to all GS cDNAs amplified from cv. Peredovic, except to cDNAs III and IV, were detected in the inbred line R41. This result strongly suggests that the three cDNAs for chloroplastic isoform are allelic sequences from the same locus, and since cDNA type IV contains sequences derived from cDNAs II and III, it indicates a recombinational origin. The results presented are consistent with the existence of a GS gene family in sunflower with at least five members. Four of them, named ggs1.1 to ggs1.4, codify for the cytosolic isoforms (cDNAs I, V, VI and VII). A fifth member, named ggs2, from which three allelic sequences (cDNAs II, III and IV) have been cloned, encodes the chloroplastic isoform. This revised version was published online in July 2006 with corrections to the Cover Date.