Activation of human c-raf-1 by replacing the N-terminal region with different sequences.

Two transformants of NIH 3T3 cells, obtained by the transfection of human colon cancer and normal colon DNAs, contained activated c-raf-1. In both the activated c-raf-1, the 5' half of the c-raf-1 sequence was replaced by sequences other than c-raf-1 as a result of recombinations which occurred at the intron between exons 7 and 8. It was suggested, however, that these recombinations, which conferred the transforming activity on the c-raf-1, occurred during the transfection. In one case analyzed, characteristic sequences were found near the breakpoint and these may be involved in the recombination. It was found, upon analysing the structure of the cDNA derived from one of the activated c-raf-1, that fused mRNA had been transcribed from the recombined gene comprising the non-raf gene and c-raf-1. The mRNA possibly encodes a fused protein. One cDNA clone was derived from alternatively spliced mRNA, although its physiological role is unclear. On comparing the structure of the two human activated c-raf-1 and the rat activated c-raf which we have reported previously, it was revealed that, in these three cases, the sequences joined to the truncated c-raf(-1)1 were different. It was suggested from data which we and others have previously reported that various sequences could be capable of activating c-raf(-1) by replacing its 5' half.     

DNA repair in higher plants; photoreactivation is the major DNA repair pathway in non-proliferating cells while excision repair (nucleotide excision repair and base excision repair) is active in proliferating cells

We investigated expression patterns of DNA repair genes such as the CPD photolyase, UV-DDB1, CSB, PCNA, RPA32 and FEN-1 genes by northern hybridization analysis and in situ hybridization using a higher plant, rice (Oryza sativa L. cv. Nipponbare). We found that all the genes tested were expressed in tissues rich in proliferating cells, but only CPD photolyase was expressed in non-proliferating tissue such as the mature leaves and elongation zone of root. The removal of DNA damage, cyclobutane pyrimidine dimers and (6–4) photoproducts, in both mature leaves and the root apical meristem (RAM) was observed after UV irradiation under light. In the dark, DNA damage in mature leaves was not repaired efficiently, but that in the RAM was removed rapidly. Using a rice 22K custom oligo DNA microarray, we compared global gene expression patterns in the shoot apical meristem (SAM) and mature leaves. Most of the excision repair genes were more strongly expressed in SAM. These results suggested that photoreactivation is the major DNA repair pathway for the major UV-induced damage in non-proliferating cells, while both photoreactivation and excision repair are active in proliferating cells.     

Role of pollination in yield and physicochemical properties of tomatoes (Lycopersicon esculentum)

Very little is known about pollination and its effects on the yield and physicochemical properties of flowering plants in tropical countries. Wind and insect pollinators are among our natural resources because pollination is the most important ecosystem service performed by wind and insects, and is vital to the socio-economic status of human beings. In this experiment, different pollination methods for tomato plants were examined. Self-pollination was encouraged by covering the plants with a plastic sheet. Wind and insects were excluded from these plants, and thus only self-pollination was possible. The experiment occurred during the flowering stage. Wind-pollinated plants were covered with a muslin cloth, which excluded insects, and only wind could pass through the cloth. For insect pollination, plants remained uncovered, allowing free access to insects to pollinate the flowers. At fruit maturity, when fruits were completely red, fruits from each treatment were harvested on the same date and under the same conditions. Results illustrated the substantial importance of insects as pollinators of tomato crops. Open field had greater tomato yield and positive effects on physicochemical properties on fruit than under self and wind pollination.     

Terminal drought and seed priming improves drought tolerance in wheat

Plants retain the preceding abiotic stress memory that may aid in attainment of tolerance to subsequent stresses. This study was conducted to evaluate the influence of terminal drought memory (drought priming) and seed priming in improving drought tolerance in wheat (Triticum aestivum L.). During first growing season, wheat was planted in field under optimal (well-watered) and drought stress imposed at reproductive stage (BBCH growth stage 49) until maturity (BBCH growth stage 83). Seeds collected from both sources were subjected to hydropriming or osmopriming (with 1.5% CaCl₂ solution); while, dry seed was taken as control. Treated and control seeds, from both sources, were sown in soil filled pots. After the completion of seedling emergence, pots were maintained at 50% water holding capacity (drought) or 100% water holding capacity (well-watered). Drought stress suppressed the plant growth (2–44%), perturbed water relations (1–18%) and reduced yield (192%); however, osmolytes accumulation (3–14%) and malondialdehyde contents (26–29%) were increased under drought. The crop raised from the seeds collected from terminal drought stressed plants had better growth (5–63%), improved osmolyte accumulation (13–45%), and lower lipid peroxidation (3%) than the progeny of well-watered crop. Seed priming significantly improved the crop performance under drought stress as compared to control. However, osmopriming was more effective than hydropriming in this regard as it improved leaf area (9–43%), tissue water status (2–47%), osmolytes accumulation (6–48%) and grain yield (14–79%). In conclusion, terminal drought induced modifications in seed composition and seed priming improved transgenerational drought tolerance through improvement in tissue water status and osmolytes accumulation, and decrease in lipid peroxidation.     

Presence of nitrosable mutagen precursors in cooked meat and fish

Broiled chicken, pork, mutton, beef and sun-dried sardine were found to yield direct-acting mutagenicity after nitrite treatment. When 50% methanol extracts of cooked foods were treated with 50 mM nitrite at pH 3 for 1 h at 37 degrees C, they induced 3800-17,900 revertants of Salmonella typhimurium TA100 and 15,000-43,600 revertants of TA98 per g. In contrast, raw meat and uncooked sun-dried sardine showed little or no mutagenicity after nitrite treatment. Treatment of broiled chicken with 0.5-3 mM nitrite, which is a physiologically feasible concentration in the human stomach under some conditions, induced direct-acting mutagenicity. When broiled chicken was treated with 1 mM nitrite at pH 3 for 1 h at 37 degrees C, its mutagenicities on TA100 and TA98 without S9 mix were 7100 and 5400 revertants/g, respectively.     

Morphological and physiological response of tomato (Solanum lycopersicum L.) to natural and synthetic cytokinin sources: a comparative study

Among the natural plant growth stimulants, moringa has attained enormous attention due to its leaf composition being enriched with cytokinin, antioxidants and minerals. Exogenous application of moringa leaf extract (MLE) improves productivity in many crops. This study investigated the potential of MLE with different dilutions, i.e., MLE0, MLE10, MLE20 and MLE30 (0, 10, 20 and 30 times diluted in water, respectively) to improve the performance of tomato. Foliage-applied water and benzylaminopurine (BAP, 50 mg L^?1) were taken as controls. Among treatments, foliar-applied MLE30 produced maximum vegetative and flowering branches, number of flowers and heaviest fruits per plant of tomato in comparison with synthetic BAP and other treatments. A similar increase in vegetative and flowering branches was recorded for root-applied MLE20 including BAP. Foliage-applied MLE30 also increased chlorophyll (a) pigments and leaf total soluble proteins than other stimulants used. This increase was followed by enhanced antioxidant activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), total phenolics in leaves and fruit lycopene contents of tomato. In general, foliar application of MLE30 was more effective as natural biostimulant to improve growth, productivity and fruit quality of tomato as compared to synthetic BAP and its root application.