Effects of growth regulators on light-dependent anthocyanin production in Zea mays seedlings

Rengel, Z. and Kordan, H. A. 1987. Effects of growth regulators on light-dependent anthocyanin production in Zea mays seedlings.
The effects of ethylene, indolyl- and naphthylacetic acids, zeatin, benzyladenine, gib-berellic acid and triiodobenzoic acid on anthocyanin production in seedlings of Zea mays L. cv. Golden Bantam were investigated. Endogenously produced and exogen-ously supplied ethylene, as well as the other growth regulators tested markedly suppressed anthocyanin formation. Except for triiodobenzoic acid, the other growth regulators stimulated ethylene production, the amounts produced in the light being larger than those in the dark. Absorption of ethylene by permanganate as well as inhibition of ethylene production or action by Co²⁺ or Ag⁺ increased anthocyanin formation in maize seedlings above the level found in the control plants. The inhibiting effect of auxins and cytokinins on anthocyanin production was reversed by Co²⁺ or Ag⁺. In contrast, decreased anthocyanin formation caused by gibberellic acid or triiodobenzoic acid seemed unrelated to ethylene and could not be alleviated by Co²⁺ or Ag+.     

Effect of valproate on lactate and glutamine metabolism by rat renal cortical tubules

The metabolic effects of sodium valproate (VPA) on rat renal cortical tubules have been examined. When 1 or 5 mM lactate was used as substrate in the incubation medium, VPA decreased markedly the lactate uptake by the tubules. When 1 or 5 mM glutamine was used, the addition of VPA accelerated glutamine uptake, ammoniagenesis, but also stimulated markedly the accumulation of lactate and pyruvate produced from glutamine. VPA had a dose-dependent inhibitory effect on gluconeogenesis from both glutamine and lactate. With 5 mM glutamine, VPA also induced a significant accumulation of glutamate in the medium. The oxygen consumption by the tubules was diminished by 40% following VPA addition. It is concluded that VPA modifies the metabolism of rat cortical tubules by interfering with the oxidation of natural substrates and stimulates in this fashion the production of ammonia by kidney tubules.     

Net Mg2+ uptake in relation to the amount of exchangeable Mg2+ in the Donnan free space of ryegrass roots

Ammonium acetate and BaCl₂-triethanolamine were used to desorb Mg²⁺ from the root Donnan free space (DFS) of 23-d-old ryegrass (Lolium multiflorum Lam. cvs. Gulf and Wilo). Amounts of desorbed Mg²⁺ increased with the increase in Mg²⁺ activity of the nutrient solution. Slightly less Mg²⁺ was desorbed by Ba²⁺ than by NH₄ ⁺. Previously published data on short-term net Mg²⁺ uptake by intact 23-d-old ryegrass plants of the two cultivars were linearly related to the amount of exchangeable Mg⁺ desorbed from the root DFS (r²=0.90 and 0.81 for the desorption by NH₄ ⁺ and Ba²⁺, respectively). A sward of Mg²⁺ ions attracted to the negative charges of the cell surface is suggested to represent a part of a pool of Mg²⁺ available for active transport through the plasmalemma.     

Competitive Al Inhibition of Net Mg Uptake by Intact Lolium multiflorum Roots : II. Plant Age Effects

Rhizotoxicity of Al is more pronounced in younger plants. Effects of Al on nutrient uptake by plants of different age are poorly understood. The depletion technique was used to monitor net Mg²⁺ uptake from nutrient solutions by intact 15- and 35-day-old plants of two ryegrass (Lolium multiflorum Lam.) cultivars. Lowering the pH from 6.0 to 4.2 decreased the maximum net ion influx without affecting K_m. Aluminum at 6.6 micromolar Al³⁺ activity increased K_m indicating competitive inhibition. The effects of pH and 6.6 micromolar Al³⁺ on net Mg²⁺ uptake were much larger in 15- than in 35-day-old plants. Aluminum at 26 micromolar Al³⁺ activity competitively inhibited net Mg²⁺ uptake by 35-day-old plants, while causing time- and external Mg²⁺ activity-dependent net Mg²⁺ efflux from 15-day-old plants. The equilibrium constant (K_i) of a reversible combination of postulated plasmalemma Mg²⁺ transporter and Al³⁺ was calculated to be 2 and 5 micromolar Al³⁺ activity for 15-day-old plants of Wilo and Gulf ryegrass, respectively, and 21 micromolar Al³⁺ activity for 35-day-old plants of both cultivars. The Al³⁺-mediated increase in K_m was larger for 15-day-old plants of the Al-sensitive cultivar `Wilo' than of the more Al-tolerant cultivar `Gulf,' while Al³⁺ affected 35-day-old plants of both cultivars to the same extent.     

Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat

A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur, Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg⁻¹ of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg⁻¹ live chaff-inoculum and control having 0.1 g kg⁻¹ dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg⁻¹ applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg⁻¹ for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05 mg Zn kg⁻¹ soil) and medium (0.5 mg Zn kg⁻¹ soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg⁻¹ soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana     

Time-course of Biosynthesis of Phenolics and Lignin in Roots of Wheat Genotypes Differing in Manganese Efficiency and Resistance to Take-all Fungus

Inhibition of lignin biosynthesis in Triticum aestivum L. rootsby Mn deficiency has been suggested as the mechanism of reducedresistance of Mn-deficient wheat roots to infection by the take-allfungus (Gaeumannomyces graminis var. tritici). This study evaluatedphenolics and lignin accumulation in roots of wheat genotypesdiffering in Mn efficiency (measured as growth and yield inMn-deficient soils) and take-all resistance. Seedlings of theMn-inefficient, take-all sensitive genotype Bayonet and theMn-efficient, more take-all resistant genotype C8MM were grownin nutrient solution without added Mn for 18 d and then transferredto a Mn-deficient sandy soil fertilized with Mn at 0 or 30 mgkg^-1. Both genotypes had Mn-deficient roots and shoots at thetime of transfer to the soil. Roots of both genotypes were inoculatedwith the take-all fungus 0, 1, 3 and 7 d after transfer. Twenty-fourhours after inoculation, take-all fungus penetrated the rootstele of take-all sensitive Bayonet but not of more resistantC8MM wheat. Rates of phenolics and lignin accumulation in rootsdeclined steadily during growth in soil for up to 8 d, werehigher in mature, fully differentiated parts of the root systemcompared to distal, younger root tissue, and were higher inBayonet than in C8MM. Manganese fertilization did not significantlyinfluence rates of phenolics and lignin accumulation but reduceddepth of radial penetration by hyphae in both genotypes. Therate of phenolics accumulation was positively (r = 0·91to 0·96) correlated with the rate of lignin accumulation.Mn-efficient C8MM had a higher rate of lignin accumulation perunit of phenolics than Mn-inefficient Bayonet over a wide rangeof phenolics synthesis rates. From this we suggest that C8MMhas a more efficient mechanism for conversion of phenolics tolignin, the trait which appears related to higher take-all resistanceof this genotype.Copyright 1994, 1999 Academic Press Gaeumannomyces graminis var. tritici, lignin, manganese, phenolics, resistance, roots, Triticum aestivum     

Importance of seed Zn content for wheat growth on Zn-deficient soil

Eggplants (Solanum melongena L. cv. Bonica) were grown in a glasshouse during summer under natural light with one unbranched shoot or one shoot with 3 to 4 branches and with or without fruit in quartz sand buffered and not buffered with 0.5% CaCO₃ (w : v), respectively. Nutrient solutions supplied contained nitrate or ammonium as the sole nitrogen source. Compared with nutrient solutions containing nitrate (10 mM), solutions containing ammonium (10 mM) caused a decrease in net photosynthesis of eggplants during early stages of vegetative growth when grown in quartz sand not buffered with CaCO₃. The decrease was not observed before leaves showed interveinal chlorosis. In contrast, net photosynthesis after bloom at first increased more rapidly in eggplants supplied with ammonium than with nitrate nitrogen. However, even in this case, net photosynthesis decreased four weeks later when ammonium nutrition was continued. The decrease was accompanied by epinasty and interveinal chlorosis on the lower leaves and later by severe wilting, leaf drop, stem lesions, and hampered growth of stems, roots, and fruits. These symptoms appeared later on plants not bearing fruits than on plants bearing fruits. If nutrient solutions containing increasing concentrations of ammonium (0.5–30 mM) were supplied after the time of first fruit ripening, shoot growth and set of later flowers and fruits were promoted. In contrast, vegetative growth and reproduction was only slightly affected by increasing the concentration of nitrate in the nutrient solutions. In quartz sand buffered with CaCO₃ ammonium nutrition caused deleterious effects only under low light conditions (shade) and on young plants during rapid fruit growth. If eggplants were supplied with ammonium nitrogen before bloom, vegetative growth was promoted, and set of flowers and fruit occurred earlier than on plants supplied with nitrate. Furthermore, the number of flowers and fruit yield increased. These effects of ammonium nutrition were more pronounced when plants were grown with branched shoots than with unbranched shoots. The results indicate that vegetative and reproductive growth of eggplants may be manipulated without causing injury to the plants by supplying ammonium nitrogen as long as the age of the plants, carbohydrate reserves of the roots, quantity of ammonium nitrogen supplied, and pH of the growth medium are favourable. T W Rufty Section editor     

Effect of propranolol on glycerol induced acute renal failure in rats

The effect produced by propranolol, administered for a prolonged period of time and in large doses, on renal function in rats has been studied, as well as the modifications induced by this treatment in an experimental model of acute renal failure, and the effects of a single dose of propranolol given 1 hour before provoking failure. Propranolol, administered chronically, causes sodium and water retention and increases creatinine clearance. Acute renal failure induced by glycerol in rats treated for 7 days with propranolol is less severe than the one produced in untreated animals. In this ARF model, a single dose of propranolol does not seem to have a protective effect.     

Identification of novel dysregulated circular RNAs in early-stage breast cancer

Breast cancer is a major cause of cancer-related death in women worldwide. Non-coding RNAs are a potential resource to be used as an early diagnostic biomarker for breast cancer. Circular RNAs are a recently identified group of non-coding RNA with a significant role in disease development with potential utility in diagnosis/prognosis in cancer. In this study, we identified 26 differentially expressed circular RNAs associated with early-stage breast cancer. RNA sequencing and two circRNA detection tools (find_circ and DCC) were used to understand the circRNA expression signature in breast cancer. We identified hsa_circ_0006743 (circJMJD1C) and hsa_circ_0002496 (circAPPBP1) to be significantly up-regulated in early-stage breast cancer tissues. Co-expression analysis identified four pairs of circRNA-miRNA (hsa_circ_0023990 : hsa-miR-548b-3p, hsa_circ_0016601 : hsa_miR-1246, hsa_circ_0001946 : hsa-miR-1299 and hsa_circ_0000117:hsa-miR-502-5p) having potential interaction. The miRNA target prediction and network analysis revealed mRNA possibly regulated by circRNAs. We have thus identified circRNAs of diagnostic implications in breast cancer and also observed circRNA-miRNA interaction which could be involved in breast cancer development.     

Shaping chromatin for repair

To counteract the adverse effects of various DNA lesions, cells have evolved an array of diverse repair pathways to restore DNA structure and to coordinate repair with cell cycle regulation. Chromatin changes are an integral part of the DNA damage response, particularly with regard to the types of repair that involve assembly of large multiprotein complexes such as those involved in double strand break (DSB) repair and nucleotide excision repair (NER). A number of phosphorylation, acetylation, methylation, ubiquitylation and chromatin remodeling events modulate chromatin structure at the lesion site. These changes demarcate chromatin neighboring the lesion, afford accessibility and binding surfaces to repair factors and provide on-the-spot means to coordinate repair and damage signaling. Thus, the hierarchical assembly of repair factors at a double strand break is mostly due to their regulated interactions with posttranslational modifications of histones. A large number of chromatin remodelers are required at different stages of DSB repair and NER. Remodelers physically interact with proteins involved in repair processes, suggesting that chromatin remodeling is a requisite for repair factors to access the damaged site. Together, recent findings define the roles of histone post-translational modifications and chromatin remodeling in the DNA damage response and underscore possible differences in the requirements for these events in relation to the chromatin context.