Uniconazole-induced thermotolerance in soybean seedling root tissue

Soybean [Glycine max(L.) Merr. cv. A2] seeds were germinated in 0 or 1 mg 1¹ (3.4 uM) uniconazole, after which seedling roots were excised and exposed to 22 or 48°C for 90 min. Prior to the temperature treatments there were few ultrastructural differences between uniconazole-treated seedling roots and the controls. Following exposure to 48°C, electron micrographs revealed near complete loss of normal ultrastructure in control epidermal root cells, whereas cellular integrity was maintained in treated roots, indicating that uniconazole conferred tolerance to high temperature. Total electrolyte, sugar and K⁺ leakage were all greater from control roots than treated roots during exposure to 48°C. Proline content in the roots was unaffected by uniconazole at 22°C but was 25–30% greater in treated tissue than in controls following exposure to 48°C. Malondialdehyde content was unaffected by uniconazole at 22°C but was nearly 20% less in treated tissue than in controls following high temperature exposure. This indicates that uniconazole decreased high-temperature-induced lipid peroxidation. Uniconazole elevated several antiox-idant systems in the roots, including water-soluble sulfhydryl concentration and catalase, peroxidase and superoxide dismutase activities. These findings are consistent with the hypothesis that uniconazole-induced stress tolerance is due, at least in part, to enhanced antioxidant activity which reduces stress-related oxidative damage to cell membranes.     

Promotion ofin vitro shoot formation from excised roots of silktree (Albizzia julibrissin) by an oxime ether derivative and other ethylene inhibitors

Summary This report describes the regeneration response of excised seedling roots of silktree (Albizzia julibrissin) to added ethylene precursors/generators (1-amino-cyclopropane-1-carboxylic acid [ACC], 2-chloroethylphosphonic acid [CEPA]), biosynthesis inhibitors (aminoethoxyvinylglycine [AVG], an oxime ether derivative [OED={[(ispropylidene)-amino]oxy}-acetic acid-2-(methoxy)-2-oxoethyl ester], CoCl² [Co⁺⁺]), and an ethylene action inhibitor (AgNO₃ [Ag⁺]). When placed on B5 medium, about 50% of the control explants formed shoot buds within 15 days. Addition of ACC or CEPA (1–10 µM) to the culture medium decreased both the percentage of cultures forming shoots and the number of shoots formed per culture. In contrast, AVG and OED (1–10 µM) increased shoot formation to almost 100% and increased the number of shoots formed per culture. Likewise, both Co⁺⁺ and Ag⁺ (1–10 µM) increased shoot regeneration, but the number of shoots produced after 30 days was less than with AVG or OED. The inhibitors of ethylene biosynthesis were partially effective in counteracting the inhibitory effect of ACC on shoot formation. These results suggest that modulation of ethylene biosynthesis and/or action can strongly influence the formation of adventitious shoots from excised roots of silktree.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - CEPA 2-chloroethylphosphonic acid - OED oxime ether derivative     

Eco-physiological studies on Indian arid zone plants

Summary Photosynthetic characteristics of two important grasses of Indian desert have been studied. Pennisetum typhoides, an important cereal crop, known to have Kranz-type leaf anatomy and low CO₂-compensation point, shows the C-4-dicarboxylic acid pathway for photosynthetic carbon reduction. Lasiurus sindicus, a promising forage grass, has also been shown to possess, for the first time, a typical Kranz-type leaf anatomy and a very similar CO₂-fixation pattern like Pennisetum typhoides. It is remarkable that both species after short time exposure to ¹⁴CO₂ show a high labelling not only in malate but also in alanine. This may be due to the activity of an aspartic acid decarboxylase.     

Altered Diurnal Leaf Movements in Soybean Seedlings Treated with Triazole Growth Regulators

Treatment of two-week old soybean (Glycine max (L.) Merr. cv.A2) seedlings with 250 µg of either soil-applied paclobutrazolor XE-1019 (also known as S-3307) altered diurnal leaf movementswithin 48 h. Leaf blade and petiole angles of primary leaves,relative to the horizontal, were consistently lower in the triazole-treatedseedlings compared to controls during the daylight hours. Atnight, leaves were completely folded down in both treated andcontrol seedlings, but leaves on treated seedlings reached thefolded down position approximately two hours earlier than controls.A single foliar spray of 6.0 mg-liter^–1 GA₃ counteractedthe triazole effects on leaf blade and petiole angles. (Received February 25, 1987; Accepted July 21, 1987)     

Orthotopic transplantation of LH receptor knockout and wild-type ovaries

Luteinizing hormone (LH) receptor knockout animals have an ovarian failure due to an arrest in folliculogenesis at the antral stage. As a result, the animals have an infertility phenotype. The present study was undertaken to determine whether this phenotype could be reversed by orthotopic transplantation of wild-type ovaries. The results revealed that transplanting wild-type ovaries into null animals did not result in resumption of estrus cycles. Although the number of different types of follicles increased, none progressed to ovulation. The serum hormone profiles improved, reflecting the ovarian changes. The wild-type animals with null ovaries also failed to cycle and their ovaries and serum hormone levels were more like null animals with their own ovaries. Although the lack of rescue of null ovaries placed into wild-type animals was predicted, the failure of wild-type ovaries placed in null animals was not, which could be due to chronic exposure of transplanted tissue to high circulating LH levels and also possibly due to altered internal milieu in null animals. These findings may have implications for potential future considerations of grafting normal donor ovaries into women who have an ovarian failure resulting from inactivating LH receptor mutations.     

Spectrum of MECP2 gene mutations in a cohort of Indian patients with Rett syndrome: Report of two novel mutations

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder, primarily affecting females and characterized by developmental regression, epilepsy, stereotypical hand movements, and motor abnormalities. Its prevalence is about 1 in 10,000 female births. Rett syndrome is caused by mutations within methyl CpG-binding protein 2 (MECP2) gene. Over 270 individual nucleotide changes which cause pathogenic mutations have been reported. However, eight most commonly occurring missense and nonsense mutations account for almost 70% of all patients. We screened 90 individuals with Rett syndrome phenotype. A total of 19 different MECP2 mutations and polymorphisms were identified in 27 patients. Of the 19 mutations, we identified 7 (37%) frameshift, 6 (31%) nonsense, 14 (74%) missense mutations and one duplication (5%). The most frequent pathogenic changes were: missense p.T158M (11%), p.R133C (7.4%), and p.R306C (7.4%) and nonsense p.R168X (11%), p.R255X (7.4%) mutations. We have identified two novel mutations namely p.385-388delPLPP present in atypical patients and p.Glu290AlafsX38 present in a classical patient of Rett syndrome. Sequence homology for p.385-388delPLPP mutation revealed that these 4 amino acids were conserved across mammalian species. This indicated the importance of these 4 amino acids in structure and function of the protein. A novel variant p.T479T has also been identified in a patient with atypical Rett syndrome.     

Effect of gibberellin biosynthesis inhibitors on shoot regeneration from hypocotyl explants of Albizzia julibrissin

Summary Hypocotyl explants of Albizzia julibrissin were placed on Gamborg's B5 medium supplemented with various levels of paclobutrazol, uniconazole, prohexadione calcium, or GA₃. Callus formation was evident within one week after placement of the explants on the culture media. Green nodule-like structures protruded from the distal end of the explants within 10 days and developed into shoots within a month. These shoots readily formed adventitious roots when placed on fresh culture medium. All three of the gibberellin biosynthesis inhibitors increased shoot formation compared to the control. The number of shoots per explants was increased 107, 79, and 168% by 0.3–0.4 μM paclobutrazol, uniconazole, and prohexadione calcium, respectively. In contrast to the gibberellin biosynthesis inhibitors, GA₃ decreased shoot formation. These results indicate that modification of gibberellin status can have a strong impact on the number of shoots formed.     

Heat shock tolerance and antioxidant activity in moth bean seedlings treated with tetcyclacis

Moth bean (Vigna aconitifolia (Jacq.) Marechal cv. Jaadia) seeds were germinated in the presence of 0, 18, or 36 M solutions of the gibberellin biosynthesis inhibitor, tetcyclacis. After 72 h, seedlings were exposed to 22 or 48°C for 90 min. The 48°C temperature dramatically increased total electrolyte and sugar leakage from the seedlings, particularly in the controls. Tetcyclacis reduced electrolyte and sugar leakage at 48°C by 15–35% compared to the 48°C controls. High temperature increased malondialdehyde concentration in control seedlings but not in treated seedlings indicating that tetcyclacis inhibited high temperature-induced lipid peroxidation. Relative to the control, tetcyclacis tended to increase the total activities of catalase and peroxidase in the seedlings. In contrast, tetcyclacis tended to decrease ascorbic acid oxidase activity, particularly at 48°C. These results suggest that tetcyclacis conferred at least some heat shock tolerance to moth bean seedlings. This increased tolerance was correlated with increased activities of some antioxidant systems.