Isoenzyme Patterns of Root and Shoot in the Early Growth of Wheat

Isoenzyme patterns of peroxidase, catalase, glucose-6-phosephate, glutamate and isocitrate dehydrogenases, esterase, amylase and IAA oxidase in the embryos, endosperms, roots and shoots of wheat seedlings (Triticum aestivum L. var. Nung-da 139) were determined by horizontal starch gel electrophoresis and polyacrylamide gel disc electrophoresis respectively. The number of isoenzymes of peroxidasc and amylase was increased with the concomitant increase of days during germination. The isoenzyme bands of esterase, glutamate, glucose-6-phosphate and isocitrate dehydrogenases in the embryos were more in the begining of germination. The activities of pero- xidase, IAA oxidase and glutamate dehydrogenase in roots were higher than those in shoots. On the contrary, the activities of catalase and glucose-6-phosphate dehydrogenase in shoots were higher than those in roots. However the activity of esterasc was slight higher in shoots. There was no difference in the activity of isocitrate dehydrogenase between roots and shoots. The morphological difference of shoot and root is evidently related to isoenzyme patterns. This investigation indicates that different metabolic characters are existed in shoot and root during differentiation.     

Endogen und exogen ausgelöste Änderung des Isoenzymspektrums der NAD-spezifischen Glutamatdehydrogenase im Sproß von Pisum sativum

Summary The isoenzymes of NAD-specific glutamic dehydrogenase (GDH) of Pisum sativum, separated by polyacrylamide gel electrophoresis, constitute two patterns, each of which covers seven individual isoenzymes. One pattern (GDH-I) is found in the cotyledons and young shoots. The second one (GDH-II) occurs together with at least some GDH-I isoenzymes in pea roots. In the shoots of older pea plants GDH-II isoenzymes become visible in addition to the GDH-I pattern.Section of the cotyledons (but not of the roots) of young pea seedlings causes the formation of the complete GDH-II isoenzyme pattern in the shoots within a few hours. It has been verified that the cotyledons specifically suppress the formation of the GDH-II pattern in the young shoot. In older plants which no longer depend on the cotyledons this effect is maintained somewhat less obviously by the root system.In experiments with isolated shoot segments or shoot tips it has been shown that NH ₄ ⁺ reinforces the formation of the GDH-II whereas glucose shows the opposite effect.The formation of the GDH-II isoenzymes in the presence of NH ₄ ⁺ is accompanied by an increase of the specific activity of GDH. Simultaneously the ratio of aminating activity (anabolic reaction) to deaminating activity (catabolic reaction) changes in favor of the anabolic reaction.The results support the supposition that the GDH-I and GDH-II isoenzyme patterns correspond to different molecular forms of one enzyme, the GDH-II representing a form with predominantly anabolic function and the GDH-I a form which has merely metabolic or catabolic function.     

Biosynthesis of lectin in roots of germinating and adult cereal plants

Root tips of wheat, rye, barley and rice seedlings contain lectins which are identical to the respective embryo lectins with respect to their molecular weight, sugar-specificity and serological properties. Using in vivo labelling techniques, it could be demonstrated that lectin is synthesized de novo in these tissues. The presence of lectin mRNA in seedlings was confirmed by in-vitro synthesis of lectin in root-tip extracts. Lectin synthesis occurs both in primary and first adventitious roots and is confined to the apical part (2mm) of the root. As seedling development proceeds, lectin synthesis in root tips gradually decreases. Adventitious roots of adult (five to six months old) wheat, rye and barley, but not rice, plants also contain lectins which are indistinguisable from the embryo lectins by the above-mentioned criteria. These lectins are synthesized in vivo in isolated root tips (5 mm) with labelled cysteine and in vitro in cell-free extracts prepared from root tips. Synthesis of lectin in roots of adult plants is also confined to the apical (2 mm) tip of the roots. At the molecular level, root lectin synthesis is very similar to that in embryos. All root lectins are synthesized as 23 000-M_r precursors which are post-translationally converted into the mature 18 000-M_r polypeptides. The observation that seedling roots and adventitious roots of six-month-old plants actively synthesize lectins strongly indicates that lectin genes are expressed in these tissues. In addition, since the root lectins are indistinguishable from the embryo lectins, we postulate that the same lectin genes are expressed.Abbreviations ABA abscisic acid - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - WGA wheat-germ agglutinin     

二氢血根碱对莴苣幼苗根生长及其细胞分裂的影响

以莴苣幼苗为受体,用培养皿法检测从细果角茴香中分离得到的二氢血根碱对莴苣幼苗根生长和根毛发育的影响,并采用根尖细胞有丝分裂检测和单细胞凝胶电泳法对其可能的作用机制进行了初步研究.结果显示:较低浓度(25、50μmol/L)二氢血根碱能显著促进莴苣根的生长,较高浓度(200、300μmol/L)二氢血根碱显著抑制根的生长;二氢血根碱(10、20、30、40、50μmol/L)对莴苣幼苗根毛发育有极显著的抑制作用,且两者均表现了浓度依赖性.较低浓度(25、50μmol/L)二氢血根碱使根尖细胞有丝分裂指数显著增加,而对根尖细胞DNA没有显著影响;较高浓度(200、300μmol/L)二氢血根碱使根尖细胞有丝分裂指数显著下降,同时根尖细胞DNA受到显著性损伤.研究发现,低浓度的二氢血根碱对莴苣幼苗根生长的促进作用主要是由于根尖细胞有丝分裂活力增加所致;而高浓度二氢血根碱对莴苣幼苗根的抑制作用极可能是由于根尖细胞DNA受到损伤,使得细胞分裂活力降低,分裂期细胞数目减少,从而导致根生长受到抑制.     

Subcellular Location of O-Acetylserine Sulfhydrylase Isoenzymes in Cell Cultures and Plant Tissues of Datura innoxia Mill

O-Acetylserine sulfhydrylase (OASS; EC 4.2.99.8) catalyzes the formation of L-cysteine from O-acetylserine and inorganic sulfide. Three OASS isoenzymes that differ in molecular mass and subunit structure are present in shoot and root tissues and in cadmium-resistant and cadmium-susceptible cell cultures of Datura innoxia Mill. Different OASS forms predominate in leaves, roots, and suspension-cell cultures. To determine the subcellular location of the OASS isoenzymes, purified mitochondria, chloroplasts, and cytosolic fractions from protoplasts were obtained. The isoenzymes are compartmentalized in D. innoxia cells, with a different isoenzyme predominant in the chloroplast, cytosol, and mitochondria, suggesting that they serve different functions in the plant cell. The chloroplast form is most abundant in green leaves and leaf protoplasts. The cytosolic form is most abundant in roots and cell cultures. A mitochondrial form is abundant in cell cultures, but is a minor form in leaves or roots. Cadmium-tolerant cell cultures contain 1.8 times as much constitutive OASS activity as the wild-type cell line, and 2.9 times more than the cadmium-hypersensitive cell line. This may facilitate rapid production of glutathione and metal-binding phytochelatins when these cultures are exposed to cadmium.     

Immunocharacterization of NADH-Glutamate Dehydrogenase from Vitis vinifera L

Rabbit antiserum was raised against NADH-glutamate dehydrogenase (GDH) isoenzyme 1, purified from leaves of Vitis vinifera L. cv Soultanina and its specificity was tested. This antiserum was used for immunocharacterization of the GDH from leaf, shoot, and root tissues. The antiserum recognized the seven isoenzymes of NADH-GDH and precipitated all the enzyme activity from the three tissues tested. Western blot following SDS-PAGE revealed the same protein band for the three tissues, with a molecular mass of 42.5 kilodaltons corresponding to NADH-GDH subunit. Results, based on the immunological studies, revealed that NADH-GDH from leaf, shoot, and root tissues are closely related proteins. Furthermore, addition of ammonium ions to the culture medium of in vitro grown explants resulted in a significant increase in NADH-GDH activity in root, shoot, and leaf tissues.     

RML1 and RML2, Arabidopsis genes required for cell proliferation at the root tip.

New cells are produced from the meristematic tissues located at the shoot and root tip throughout the life of higher plants. To investigate the genetic mechanism regulating meristematic activity, we isolated and characterized four single-gene, recessive mutants in Arabidopsis thaliana called root meristemless (rml). Complementation tests identified two RML loci; RML1 maps to chromosome IV and RML2 maps to chromosome III. These mutants produce normal embryonic roots that either did not undergo or experienced limited cell division following germination, resulting in primary roots of less than 2.0 mm in length. Mutants can produce lateral and adventitious roots, which can grow to a length comparable to the embryonic root and arrest, indicating that the growth arrest is unrelated to the embryonic dormancy process. Neither the addition of growth regulators to the media nor the removal of shoots can rescue mutant roots from growth arrest, indicating that the mutant phenotype is not caused by a shortage of known growth regulators or by a transmissible shoot inhibitor. Normal cell division ability in mutant embryo, shoot, and callus cells indicates that the RML gene functions are not part of the general cell division processes; rather, they are involved specifically in activating the cell division cycle in the root apical cells.     

Tomato (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> cv. pera) hairy root cultures: Characterization and changes in peroxidase activity under NaCl treatment

Summary Hairy root cultures of Lycopersicon esculentum L. Mill ev. Pera were established by infection of leaf explants with Agrobacterium rhizogenes LBA 9402. The pattern of peroxidase isoenzymes in these tissues was similar to that of roots excised from tomato plants grown in hydroponic cultures. Hairy root cultures may be an appropriate system to analyze the peroxidase involvement in the response of isolated roots to salt stress, avoiding the problem of wounding or changes in hormone levels observed in roots excised from plants. The cultures of hairy roots allowed the evaluation of changes in peroxidase patterns not only in the tissue but also in the culture medium. Hairy roots were subcultured in Murashige and Skoog liquid medium with or without 100 mM NaCl to investigate the evolution of growth, total peroxidase activity of the tissue and culture medium, and changes in the peroxidase isoenzyme patterns under each condition of growth. Control cultures showed a growth index higher than those reported for other hairy root cultures, and it was even higher in the presence of 100 mM NaCl. The total peroxidase activity in the tissue was similar for control and salt-treated roots. Even when the total peroxidase activity of the medium decreased under salt treatment, NaCl induced secretion of a highly basic peroxidase and inhibition of the secretion of some acidic isoenzymes. These changes may explain the physiological role of these enzymes in the response to salt stress that we will possibly establish through a future study of the biochemical properties of those peroxidases.     

Changes in growth and structure of pea primary roots (Pisum sativum L. cv. Alaska) as a result of sudden flooding

Pea (Pisum sativum L. cv. Alaska) primary roots were exposed to flooding after growth for 4 or 5 d at 25 degrees C under relatively dry conditions. Flooding after 4 d growth reduced, but did not stop, primary root growth, and cavities caused by degradation of central vascular cells were typically found from 10-60 mm from the tips. Flooding after 5 d stopped primary root growth and caused cell death in the tips, and vascular cavities formed that typically were 20-60 mm from the tips of the roots. Degradation of root tip cells in 5-day-roots was very rapid and began in the elongation zone and later in the apical zone. Root tips discolored, narrowed or curled before growth arrest. The mitotic indices of 5-day-root tips were suppressed by the flooding treatment. A few mitotic figures were observed in roots treated with flooding after 4 d growth. Affected cells had condensed nuclei, but cytoplasms appeared to be normal in the early stages of cell degradation. Later these cells became very vacuolated. The relationship of flooding to root growth, vascular cavity formation, and the morphology of pea primary roots is described with regard to the ability to resist flooding stress.     

Cu2O纳米颗粒对小麦根系形态及遗传毒性的影响

为了阐明Cu₂O纳米颗粒(NPs)暴露对植物根系的毒性效应,本研究以小麦品种‘周麦18’为材料,采用水培试验方法,研究了10、50、100和200 mg·L^-1浓度的Cu₂O-NPs对小麦幼苗生长、根系活性、形态结构及细胞遗传学毒性的影响。结果表明: 不同浓度的Cu₂O-NPs降低了小麦幼苗的根芽长度、鲜重、根活性和根冠比,增加了初生根的数量;随着Cu₂O-NPs浓度的升高,幼苗根伸长区缩短、根系变硬变脆、根径增加、根冠变大;100 mg·L^-1浓度的Cu₂O-NPs处理下,小麦根尖有丝分裂指数显著降低,根尖细胞形状不规则化、质壁分离、细胞出现空泡化、细胞核核膜模糊、核内染色体异常。在水培条件下,Cu₂O-NPs对小麦幼苗具有一定的遗传学毒性效应,从而影响小麦幼苗的生长发育和根系形态结构。     

Studies on the initiation of adventitious roots on mung bean hypocotyl

During the early stages of root induction in hypocotyls of mungbean cuttings, four new peroxidase isoenzymes are formed inthat part of the cutting that produces roots. These isoenzymesare in addition to and different from the three already presentin the hypocotyl. Forty-eight hr is required for the changeto take place from the original three to seven isoenzymes. Thechange in isoenzyme pattern and root initiation itself are retardedwhen streptomycin is applied during the very early stages ofroot induction. However, during the latter part of the first24-hr period after the cutting is made and when some of thenew isoenzymes have already been formed, the rooting processbecomes insensitive to this antibiotic. Cytologically, the occurrenceof cell division is paralleled by the formation of the fournew peroxidase isoenzymes. The delay in the occurrence of celldivision caused by the presence of streptomycin is paralleledby a similar delay in the formation of the four new isoenzymes. (Received November 27, 1970; )     

二氧化硫衍生物对蚕豆幼苗生长和细胞周期的影响

研究SO₂体内衍生物NaHSO₃与Na₂SO₃(1:3,mmol/L)对蚕豆幼苗生长和细胞分裂的影响。结果表明:SO₂衍生物(浓度在0~30mmol/L)对幼苗生长的抑制作用具有剂量效应和时间效应关系,短时间处理效应不明显,处理48h后蚕豆幼根生长抑制,168h后幼苗根上部分长度(芽长)表现生长抑制,根长和芽长与处理浓度间呈负线性相关。SO₂衍生物处理12~36h,导致根尖细胞分裂指数下降,根尖中前期细胞减少,间期、后期和末期细胞增多,表明SO₂衍生物能够阻止细胞进入分裂态,延长分裂过程,这可能是SO₂衍生物处理组根尖细胞分裂指数降低,幼苗生长抑制的主要原因。     

Ferulic acid impairs rhizogenesis and root growth,and alters associated biochemical changes in mung bean (Vigna radiata) hypocotyls

The present study investigated the effect of ferulic acid (FA; 0–1000 µM) on early growth, and rhizogenesis in mung bean (Vigna radiata) hypocotyls and associated biochemical changes. FA severely affected the radicle elongation and number of secondary roots after 72 h. The root and shoot length, number and length of secondary roots, and seedling dry weight of one-week-old seedlings of mung bean were decreased by 64%. The rooting potential (percent rooting, number and length of adventitious roots) of mung bean hypocotyls under in vitro conditions was significantly inhibited in response to 1–100 µM FA. At 1000 µM there was complete cessation of rooting. FA caused a reduction in the contents of water-soluble proteins and endogenous total phenolics, whereas the activities of proteases, peroxidases, and polyphenol peroxidases increased. The study concludes that FA inhibits root growth and development, and in vitro rooting process in mung bean by interfering with biochemical processes that are crucial for root formation.     

Effect of benzylaminopurine on in vitro and in vivo root development in lentil, Lens culinaris Medik

The effect of benzylaminopurine (BAP) on the formation of roots from lentil shoots regenerated on media containing BAP was studied. Seedling shoot tips, first nodes and bractlets, and immature seeds cultured on the initiation media containing 2.25 or 0.225 mg/l of BAP regenerated multiple bud shoots. The regenerated shoots formed roots in percentages ranging from 4.6 to 39.9% on a rooting medium (R medium) containing 2 mg/l of indoleacetic acid. Rooting success on R medium depended upon the cytokinin used in the initiation media, its concentration, and the time elapsed during shoot formation on these media prior to transplanting regenerated shoots to R medium. In vivo study of root growth of lentil seedlings demonstrated the strong inhibitory effect of BAP on root growth reflected in a drastic reduction of the mitotic index of the root meristem. Received: 27 August 1996 / Revision received: 12 December 1996 / Accepted: 15 January 1997     

Lactate dehydrogenase isoenzyme transitions during skeletal differentiation in the mouse embryo

(1) In the mouse embryo there are changes in lactate dehydrogenase activity and isoenzyme pattern during the differentiation of cartilage and bone. (2) The specific activity of lactate dehydrogenase rises during chondrogenesis and falls during osteogenesis. (3) Identical isoenzyme transitions occur in parallel in both tissues: undifferentiated limb bud mesenchyme contains isoenzymes 1-5 whereas in both the cartilaginous and bony portions of a long bone developing from the mesenchyme, there is a progressive shift towards a predominance of the 'anaerobic' isoenzymes 4 and 5.     

Superoxide dismutase activity in salt stressed wheat seedlings

We investigated the effect of salt stress on enzymatic activity of superoxide dismutase (SOD) isozymes in shoot and root tissues of salt tolerant and sensitive wheat (Triticum aestivum L. and Triticum durum Defs.) cultivars. Ten day old seedlings were subjected to 0.7 M NaCl stress for 3 and 5 days. Seedlings treated in the same manner without salt stress served as controls. Activity of SOD isozymes in root and shoot extracts was determined by activity staining of native polyacrylamide gels. In both shoot and root extracts of examined cultivars two isozymes of SOD, namely MnSOD and Cu/ZnSOD were identified. Cu/ZnSOD activity comprised 90 % of total SOD activity in both root and shoot tissues. Salt stress caused 1–1.5 fold increase in MnSOD activity of shoots in tolerant cultivars when compared with non-stressed controls. Under stress conditions, compared to controls all cultivars exhibited reduced MnSOD activity in root tissues. Cu/ZnSOD activity, on the other hand, was remarkably enhanced (3–4 fold) in root extracts of the tolerant cultivars, whereas it was reduced in the sensitive ones.     

Characterisation of maize peroxidases having differential patterns of mRNA accumulation in relation to lignifying tissues

Among other enzymes, peroxidases have been proposed to participate in the latest steps of lignin biosynthesis. In order to identify new proteins involved in such mechanism of lignification in maize, we have isolated three cDNAs coding for three different peroxidases, named ZmPox1, ZmPox2, and ZmPox3, respectively. Computational analyses of these three proteins correlate with features typically attributed to heme-containing plant peroxidases of approximately 300 amino acid residues. Although with different expression levels, ZmPox2 and ZmPox3 mRNAs are accumulated in the elongating region of young roots but not in the root tips. In addition, the ZmPox2 mRNA levels are up-regulated by wounding and ethylene treatments. However, ZmPox1 is also expressed in the root tip meristems, where lignification does not occur. Finally, in situ hybridisations indicate that ZmPox2 mRNA localises in vascular tissues and epidermis. Although ZmPox1 mRNA localises in the same regions as ZmPox2 mRNA in root tips, its mRNA is only detected in the epidermis but not in the vascular tissues of young roots, suggesting that the function of ZmPox1 is not correlated to lignification. In addition, although ZmPox3 mRNA is also detected in the regions where lignification occurs, the involvement of this peroxidase in such a mechanism remains to be further investigated due to its very low expression level. Therefore, based on its amino acid sequence and mRNA accumulation and localisation patterns, the involvement of ZmPox2 in the latest steps of lignification is discussed.     

The involvement of wheat and common bean lectins in the control of cell division in the root apical meristems of various plant species

The effects of wheat germ agglutinin (WGA) and phytohemagglutinin (PHA) at the concentration of 1 mg/l on the rate of cell division in the root apical meristem of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rice (Oryza sativa L.), and common bean (Phaseolus vulgaris L.) seedlings were compared. WGA enhanced cell division in the roots of barley and rice approximately similarly as in wheat roots but did not affect division of meristematic cells in the roots of common bean seedlings. In contrast PGA enhanced mitotic activity in the root apical meristem of common bean seedlings but did not affect division in the wheat and barley roots. Seedling treatment with lectins shifted the hormonal balance in them toward accumulation of growth activators (IAA and cytokinins). The relationship between lectin and hormonal systems in the control of cell division is discussed.     

QUANTITATIVE STUDIES OF THE ROOT APICAL MERISTEM OF EQUISETUM SCIRPOIDES

An investigation was made of the meristematic activity of the apical cell, its immediate derivatives (merophytes), and of other selected cell populations of the root of Equisetum scirpoides Michx. The plane of the first division of a derivative of the apical cell is radiallongitudinal, which provides evidence that merophytes immediately adjacent to the apical cell cannot be the ultimate root initials. The apical cell is as active mitotically in roots 20–40 mm long as it is in roots that are 0.25–1 mm in length. The mitotic activity of the apical cell and of other cell populations was determined from the mitotic index, and from determination of the durations of the cell cycle and of mitosis of the apical cell by using the colchicine method of metaphase accumulation. Microspectrophotometric measurements of DNA content indicated that there was no consistent increase in DNA (endopolyploidy) in the apical cell or in the other meristematic cells as roots increased in length. Conclusion: there is no evidence that the apical cell becomes quiescent or undergoes endopolyploidy as a root increases in length.