Towards the Development of Salt Tolerant Rice Varieties by Overexpressing cDNAs From A Mangrove Plant Acanthus Ebracteatus Vahl

Rice (Oryza sativa L.) is one of the most important cereal crops in the world. Environmental stresses such as salinity are important limiting factors for crop growth and yield. Rice is a salt-sensitive crop that suffers salinity stress from germination to maturity, resulting in very poor yield. Rice varieties with high yield and tolerance to salt have to be developed to enable cultivation of rice plant on saline area. Two cDNAs encoding monodehydroascorbate reductase (AcMDHAR) and 9-cis-epoxycarotenoid dioxygenase (AcNCED) were previously isolated from a mangrove plant, Acanthus ebracteatus. These enzymes were reported to be involved in different salt tolerance mechanisms in plants. Monodehydroascorbate reductase (MDHAR), an important enzyme in the ascorbate-glutathione cycle, is involved in the salt tolerance mechanism of plants through scavenging of reactive oxygen species (ROS). While NCED is an important enzyme in the oxidative cleavage reaction of abscisic acid (ABA), a plant iv hormone which plays a vital role in stress tolerance. In this study, two overexpression vectors, pEXP32-AcMDHAR and pEXP32-AcNCED; were constructed using Gateway® technology and transformed into Taipei 309 and BRRI dhan29 rice varieties through Agrobacterium-mediated transformation, respectively. The putative transformants overexpressing AcMDHAR and AcNCED were selected in vitro using hygromycin and confirmed by PCR screening. The copy number of AcMDHAR in transgenic rice plants, ranged from single to multiple copies which was determined by real time PCR. The abundance of transcripts in transgenic rice plants was also analyzed by real time PCR. Transgenic rice plants overexpressing AcMDHAR treated at 100 mM NaCl showed significant increase in MDHAR enzyme activity compared to untransformed (UT) plants and showed tolerance to salt at germination, seedling and reproductive stages. These results implied that the overexpression of AcMDHAR in rice can enhance tolerance to salt through the increase of MDHAR enzyme activity. None of the rice plants overexpressing AcNCED showed tolerance to salt although expression was detected by real time PCR. The levels of ABA, in transgenic rice plants overexpressing AcNCED treated with 100 mM NaCl for 24 hours were similar to those in NaCl - treated UT plants. In contrast, higher levels of phaseic acid (PA), dihydrophaseic acid (DPA) and ABA- glucose ester (ABA-GE) were observed in rice plants overexpressing AcNCED compared to UT plants, indicating that ABA has been converted to PA, DPA and ABA-GE rapidly in the transgenic rice plants. These results suggested that the rapid degradation of excess ABA through self regulatory mechanisms may have caused the failure of these transgenic rice plants to exhibit salinity tolerance. v The findings of this study have provided important information towards the gene manipulation and the development of salt tolerant transgenic rice

Molecular cloning of a putative Acanthus ebracteatus- 9-cis-epoxycarotenoid deoxygenase (AeNCED) and its overexpression in rice

9-Cis-epoxycarotenoid dioxygenase (NCED) is an important enzyme which catalyzes the oxidative cleavage of abscisic acid (ABA), a plant growth regulator which plays a vital role in stress tolerance. In this study, a cDNA sequence encoding NCED from a mangrove plant (Acanthus ebracteatus) was analyzed and overexpressed in rice. Analysis of the deduced amino acid sequence of AeNCED revealed an open reading frame of 1,638 bp encoding a protein of 545 amino acids, with a 123 bp 5’-untranslated region (UTR) and a 259 bp 3’-UTR. The deduced amino acid sequence of AeNCED is more than 80% identical to the amino acid sequences of carotenoid cleavage dioxygenase from carrot, tomato, and coffee. The RNA encoding AeNCED was detected in transgenic rice (Oryza sativa cv. BRRI dhan29) plants overexpressing this cDNA. These plants only showed significantly higher tolerance to salinity at germination and better performance at seedling stages. The levels of ABA in transgenic rice seedlings overexpressing AeNCED treated with 100 mM NaCl for 24 hours were higher than those of untransformed plants. However, a higher level of dihydrophaseic acid (DPA) and ABA glucose ester (ABA-GE) were also observed in these transgenic plants suggesting that rapid degradation of ABA through a self-regulation mechanism

Mode and Departure Time Choice Behavior of Non-Work Related Trips

Non-work-related trips comprise a considerable percent of total trips, but there are a limited number of studies that investigate travel behavior related to these trips. This study investigates non-work-related travel behavior in two parts. The first part examines mode choice behavior, while the second part analyzes departure time choice. A Random Regret-Minimization (RRM) approach is applied on stated preference data that was collected in Calgary, Canada. We study mode choice behavior by examining the impacts of various sustainable neighborhood design elements like availability of vegetation/trees or shelter, speed and number of other vehicles on the streets, and the number of major intersections to cross on mode choice. We explore the impact of temperature on the non-work-related trips, particularly on active modes like walking and biking in the Canadian context. Results show that, compared to when the temperature is below 0 °C, respondents are 6% and 8% more likely to make a trip while the temperature is between 0 °C and 10 °C and higher than 10 °C, respectively. Respondents are about 4% more likely to choose an active mode when they have to cross only one or two major intersections compared to when they have to cross three or four major intersections. Respondents are about 21% more likely to choose an active mode when they have to take a road with a low speed limit and few vehicles compared to when they have to travel on roads with a low speed limit and many vehicles. Respondents are about 7% more likely to choose an active mode when they have to travel a path with ample availability of vegetation/trees or shelter compared to travelling a path with a limited availability of vegetation/trees or shelter. The effects of various sociodemographic and travel characteristics on mode choice are also discussed. We also analyzed the impacts of various categories such as individual and household sociodemographic, employment attributes, and trip characteristics on the choice of departure time. The results show that females are more likely than males to depart in afternoons and evenings, whereas males are more likely to depart in the mornings; that trips made by transit with a car and non-motorized vehicle (NMV) access are more likely to occur in the afternoon than trips made with any other travel mode; that respondents are less likely to depart in the afternoon than in the morning under snowy and rainy conditions; that respondents are more likely to depart in the afternoon when the temperature is below 0 °C than when the temperature is above 10 °C; and that respondents are more likely to depart in the afternoon and evening for trips related to grocery shopping, meals, and social/recreational events. Policy level implications of this study’s key findings are also discussed in detail

Awareness on Breast Cancer among the Women of Reproductive Age

Objective: To assess the level of awareness on breast cancer among women of reproductive age. Materials and methods: A cross-sectional descriptive study was conducted in OPD of Dhaka Medical College Hospital among the 175 respondents by face to face interview using pretested semi structured questionnaire. Results: One forth (23%) aged 21-25 years, mostly Muslim (86.3%), housewives (72.57%), had children (81.05%) and live in urban (69%) area. One third of them were illiterate and married at 16-20 years. Slightly less than half of their family income was taka 4500 to 5500. Six of 10 respondents (64%) knew that it was common cancer in women and almost all (94.29%) mentioned that breast cancer did not occur in old age. In addition half of them said that it was not inherited, signs and symptoms of breast cancer was spontaneous clear or bloody discharge from nipple often associated with a lump (61.14%), and it could not be cured (54.3%). Majority of them (78.9%) did not know that early diagnosis improves treatment outcome and the risk factor of breast cancer (65.14%). Half of them (57.5%) had knowledge that clinical breast examination as screening method of breast cancer but vast majority did not practice clinical breast examination. Only 16.67% of the respondents did BSE regularly and among them 83.33% did not know the best time for breast self examination. Practice breast feeding was universal among them but for less than 6 months. Conclusion:The study found that women were not so much aware regarding breast cancer and also preventive measures, risk factors so on. So for better awareness, campaign and counseling program from both Government and NGOs is needed.

Knowledge on Reproductive Health Issues Among the Unmarried Adolescent Girls

Objective: To assess the level of knowledge of the adolescent girls regarding reproductive health issues. Materials and methods: A cross sectional descriptive type of study was carried out among 150 unmarried adolescent girls of Vashantek slum in Dhaka city by face to face interview using a semistructured questionnaire from January to June 2008. Results: The mean age of the respondents were 16.4±2.9 years ranging from 10-19 years. Out of 150 respondents, 130 had history of menstruation and their median age of menarche was 13 years. The correct knowledge was high among the adolescent having secondary level of education than the SSC and above or primary level of education and the difference was statistically significant (p<0.05). About three-fourths of the respondents had sufficient knowledge about hygienic menstrual practice. Majority of the girls could mention the legal age of marriage. Regarding the demerits of early marriage, majority mentioned some of the demerits but not all. Three-fifths of the respondents had no knowledge on importance of family planning and regarding the methods of family planning, majority of them had no knowledge. Majority of the respondents heard the disease AIDS but regarding the knowledge on causative agent half of them had no knowledge. More than two-fifths had no knowledge on mode of transmission of AIDS. It was also found that majority of the  respondents had no knowledge on symptoms of AIDS and three-fifths had no knowledge on prevention of AIDS. Conclusion: So formal, informal and special educational program may be taken to educate the adolescent girls on reproductive health issues and government should be more concerned about this

SSR marker based genetic diversity analysis of modern rice varieties and coastal landraces in Bangladesh

33-41In Bangladesh, large cultivable areas lie in the coastal saline zone where rice cultivation is largely hindered by the salinity. This problem can be effectively addressed by identifying salt-tolerant genotypes using both conventional and modern biotechnological methods. In the present study, the genetic relationship among 24 rice (Oryza sativa L.) genotypes including Pokkali, the salt tolerant benchmark, 5 BRRI released modern varieties and some coastal landraces were assessed using 19 rice SSR markers. A total of 110 reproducible polymorphic alleles were identified from the loci with an average of 5.79 alleles per locus (range from 3-12 alleles). The polymorphism information content (PIC) values enumerated from the data obtained from allelic variation ranged from 0.3694 (RM18) to 0.8711 (RM493) with an average of 0.6533. Based on the discriminatory power value (D-value) calculated from the allelic information revealed RM493 (0.9203) as the best diagnostic PCR marker for varietal identification. The UPGMA cluster revealed six main genetic groups at a cut off value of 32% of similarities comprising of three separate clusters formed by BRRI dhan47 (Cluster III), Lolo (Cluster IV) and Purbachi (Cluster V). The reference salt tolerant cultivar Pokkali and Nonabokra clustered with 4 other tolerant and moderately tolerant rice cultivars in cluster I. The highest genetic dissimilarity was found between Pokkali and Nona (85.29%), Pokkali and Nona kochi (85.29%), and Purbachi and Nona kochi (85.29%), whereas Lona kuchi and Nona kochi (23.69%) showed the lowest genetic dissimilarity between them. DNA fingerprints of these rice cultivars by means of SSR markers provided meaningful data, which can be extended by additional SSR markers, and that information will enable maximized selection of diverse parents and assist in broadening the germplasm based on future rice breeding programmes