Rice (Oryza sativa) is sensitive to salt stresses and cannot survive under low salt conditions, such as 50 mM NaCl. In an attempt to improve salt tolerance of rice, we introduced katE, a catalase gene of Escherichia coli, into japonica rice cultivar, Nipponbare. The resultant transgenic rice plants constitutively expressing katE were able to grow for more than 14 days in the presence of 250 mM NaCl, and were able to form flower and produce seeds in the presence of 100 mM NaCl. Catalase activity in the transgenic rice plants was 1.5-to 2.5-fold higher than non-transgenic rice plants. Our results clearly indicate that simple genetic modification of rice to express E. coli-derived catalase can efficiently increase its tolerance against salt stresses. The transformant presented here is one of the most salt-tolerant rice plants created by molecular breeding so far.
Salinity stress is a major limiting factor in cereal productivity. Many studies report improvements in salt tolerance using model plants, such as Arabidopsis thaliana or standard varieties of rice, e.g., the japonica rice cultivar Nipponbare. However, there are few reports on the enhancement of salt tolerance in local rice cultivars. In this work, we used the indica rice (Oryza sativa) cultivar BR5, which is a local cultivar in Bangladesh. To improve salt tolerance in BR5, we introduced the Escherichia coli catalase gene, katE. We integrated the katE gene into BR5 plants using an Agrobacterium tumefaciens-mediated method. The introduced katE gene was actively expressed in the transgenic BR5 rice plants, and catalase activity in T 1 and T 2 transgenic rice was approximately 150% higher than in nontransgenic plants. Under NaCl stress conditions, the transgenic rice plants exhibited high tolerance compared with nontransgenic rice plants. T 2 transgenic plants survived in a 200 mM NaCl solution for 2 weeks, whereas nontransgenic plants were scorched after 4 days soaking in the same NaCl solution. Our results indicate that the katE gene can confer salt tolerance to BR5 rice plants. Enhancement of salt tolerance in a local rice cultivar, such as BR5, will provide a powerful and useful tool for overcoming food shortage problems.
ABSTRACT. Characters of the resting, the mitotic prophase and metaphase chromosomes in three species of Thymus were studied. The species studied had commonly resting chromosomes of the complex chromocenter type and mitotic prophase chromosomes of the proximal type. Thymus mongolicus showed the chromosome numbers of 2n=26 and 27 and T. przewalskii and T. roseus showed the chromosome number of 2n=26. The chromosome number of 2n=26 for T. przewalskii and that of 2n=27 for T. mongolicus were reported here for the first time and that of 2n=26 for T. roseus and T. mongilicus verified the previous reports. The chromosome number of 2n=27 for T. mongolicus seemed to have one B-chromosome as 2n=26+1B with respect to the existence of a peculiar heteropycnotic body at resting stage and high pollen stainability. Three species were commonly placed in the diploid level if the basic chromosome numbers of x=13 was accepted. Their karyotypes at mitotic metaphase were quite similar to each other regarding chromosome sizes, chromosome types according to the centromeric position and mono-modality of chromosome lengths from the longest to the shortest chromosomes except for satellite sizes. Thymus L., the Lamiaceae (Labiatae) is small subshrub plants and consists of approximately 400 species (Willis 1982). They are distributed in the temperate zone of the Eurasian continent, mainly in the Mediterranean region (Willis 1982) and grow in diabase, serpentine and calcareous rocks, limestone, in cracks rocks, on a bank, steppe, on sandy soils, xerophilous grassland, on loessic slopes and along road sides. Thymus has always been taxonomically problematic group and views concerning the taxonomic definition of the forms are extremely varied. It produces some natural hybrids. Plants of the genus is often cultivated and propagate to extract the aromatic ethereal oil and flavouring. KEYWORDS:The first cytological observation in Thymus was counting and documenting the chromosome number: 2n=24 in T. serpyllum reported by Löve and Löve (1942). Then, many more researchers have found at least 50 different chromosome numbers from 2n=14 of T. seravschanicus to 2n=90 of T. zygioides var. lycaonicus. They also have found aneuploidy in T. longedentatus as well as autoploidy in about 170 taxa included 139 species, 17 subspecies, 12 varieties and two hybrids by Löve and Löve (1942), Saaremaa (1947), Jalas (1948), Jalas and Kaleva (1966Kaleva ( , 1967, Trela-Sawicka (1968, 1970, Gogina and Svetozarova (1972), Gurzenkov (1972), Lee (1972), Jalas and Uotila (1976), Krogulevich (1978), Arrigonia et. al. (1980, Bir and Saggoo (1980), ElenaRoselló (1980), Morales Valverde (1980, 19861986a, 1990, Astanova (1981), Hruška and Bellomaria (1982), Fernandes and Leitao (1984), Funamoto et. al. (1993), Markova and Goranova (1994, Mártonfi and Mártonfiova (1996), Boscaiu et al. (1998), Tahiri et al. (1998, Constantinidis et al. (2002). Jalas (1948), Jalas and Kalev (1967) and Mártonfi and Mártonfiova (1996) and Mehrpure et al. (2002) have discussed chromosomal evolutio...
ABSTRACT. The chromosome characteristics of Filifolium sibilicum (2n=18) were studied regarding the karyotype by acetoorcein, locations of the G-C and A-T rich regions by CMA and DAPI, and FISH. The karyotypes of six representative individuals in three localities such as two sites in Inner Mongolia Autonomous Region, The People's Republic of China and one site in Buryat Republic in Russian Federation consisted commonly of 12 median-centromeric, four satellited median-centromeric and four submedian-centromeric chromosomes. CMA-stained the whole chromosomes, but four brighter bands were on terminal positions of four chromosomes and were convenient with the four sat chromosomes. DAPI-stained the whole metaphase chromosomes. Applying FISH using the biotin labeled probe of 5S rDNA and digoxigenin labeled pTa71 probe of 45S rDNA on the mitotic chromosomes showed four yellow colored signals of the 5S rDNA and four red signals that were terminally co-localized, which were obtained after hybridization of the probes with two submedian and two subterminal metaphase chromosomes.
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