Evaluation of the efficiency of somatic embryogenesis in guava (Psidium guajava L.)

Summary

An embryogenic protocol for plant regeneration of guava (Psidium guajava L.) was established using 10-week post-anthesis, zygotic embryo explants. Somatic embryogenesis was induced on Murashige and Skoog medium (MS) containing 3% (w/v) sucrose, 0.8% (w/v) agar and various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) by continuous treatment of the zygotic embryo explants. Somatic embryos appeared as globular structures at the end of the third week from culture initiation, and heart-shaped, cotyledonary-stage, and torpedo-stage embryos appeared within the next few weeks. The development of somatic embryos was asynchronous and showed five-to-seven discernible stages. Depending upon the response of the somatic embryos during their maturation, germination, acclimatisation, and encapsulation, they were grouped into one of three categories. The preferred type of somatic embryos (≥ 1.5 mm) were called the “elongated torpedo” (ET) category. The slightly less-preferred type of stomatic embryos (from 1.0 – 1.5 mm) were termed the “short torpedo” (ST) category. The least preferred types of somatic embryos, at the cotyledonary, heart-shaped, and/or globular stages of development (< 1.0 mm), were grouped into a third category designated “CHG”. The suitability and efficacy of various growth regulators and other treatments were assessed based on six different embryogenic parameters: (i) the frequency of embryogenesis; (ii) the intensity of embryogenesis, defined as the average number of somatic embryos produced per culture (“ANEPC”); (iii) the frequency of ET somatic embryos; (iv) the frequency of ST somatic embryos; (v) the frequency of CHG somatic embryos; and (vi) the overall efficiency of embryogenesis, defined as the potential of a treament to produce somatic embryos at the ET or ST stages, or at both stages of development, that could be converted into plantlets. In the present report, we found that 0.01 mg l^–1 2,4-D gave the maximum frequency and intensity of embryogenesis. But the highest frequencies of ET and ST somatic embryos were produced on MS medium containing 3% (w/v) sucrose and 0.001 mg l^–1 2,4-D, while CHG embryos were produced at the highest frequency on the same medium, but containing 0.5 mg l^–1 2,4-D. It was difficult to calculate the most effective concentration of 2,4-D for somatic embryogenesis based on parameters (i) – (v) above. Hence, quantitative estimations of the efficiency of embryogenesis (sixth parameter) were imperative in order to analyse the potential of the different treatments. The highest efficiency of somatic embryogenesis was achieved by continuous treatment of 10-week post-anthesis, zygotic embryo explants with 0.01 mg l^–1 2,4-D on full-strength MS agar medium containing 3% (w/v) sucrose. These somatic embryos matured normally on the same medium, and germinated well both on half-strength solid and in half-strength liquid MS medium containing 3% (w/v) sucrose. They grew in full-strength liquid MS medium with 3% (w/v) sucrose and showed maximum survival upon transfer to soil and hardening. Evaluations of the efficiency of somatic embryogenesis in guava, based on the six parameters defined above, have also helped us to understand and evaluate processes for high efficiency micropropagation in other species.     

Three Novel Mutations in Iranian Patients with Tay-Sachs Disease

Background: Tay-Sachs disease (TSD), or GM2 gangliosidosis, is a lethal autosomal recessive neurodegenerative disorder, which is caused by a deficiency of beta-hexosaminidase A (HEXA), resulting in lysosomal accumulation of GM2 ganglioside. The aim of this study was to identify the TSD-causing mutations in an Iranian population. Methods: In this study, we examined 31 patients for TSD-causing mutations using PCR, followed by restriction enzyme digestion. Results: Molecular genetics analysis of DNA from 23 patients of TSD revealed mutations that has been previously reported, including four-base duplications c.1274_1277dupTATC in exon 11 and IVS2+1G>A, deletion TTAGGCAAGGGC in exon 10 as well as a few novel mutations, including C331G, which altered Gln>Glu in HEXB, A>G, T>C, and p.R510X in exon 14, which predicted a termination codon or nonsense mutation. Conclusion: In conclusion, with the discovery of these novel mutations, the genotypic spectrum of Iranian patients with TSD disease has been extended and could facilitate definition of disease-related mutations. Key Words: Tay-Sachs disease, β- hexosaminidase A, β- hexosaminidase B     

Contribution of Homestead Forests to Rural Economy and Climate Change Mitigation: A Study from the Ecologically Critical Area of Cox’s Bazar—Teknaf Peninsula,Bangladesh

Small-scale Forestry - Homestead forests in the Teknaf Peninsula ecologically critical area of Cox’s Bazar in Bangladesh have not been widely studied. This paper explores floristic diversity...     

Anxiogenic behaviour induced by 17α-ethynylestradiol in male guppies (<Emphasis Type="Italic">Poecilia reticulata</Emphasis>)

Behaviour studies are used in toxicology research as they are excellent tools to measure physiological end-points caused by exogenous chemicals. In mammals both reproductive and non-reproductive behaviours have been used for a long period of time, whereas in teleost fishes non-reproductive behaviours have received little attention compared to reproductive behaviours. Recent advances in measuring stress related behaviours in zebrafish have provided additional tools to understand behaviour toxicology in fish. One species with well documented reproductive behaviour disturbed by different toxicants is the guppy, which is better suited than zebrafish for reproductive behaviour studies and therefore might be a better model organism for comparative behaviour studies in fish toxicology. Here we report new applications for non-reproductive behaviours in guppy and test these behaviours on males treated with the endocrine disruptor 17α-ethynylestradiol at environmentally relevant concentrations. 17α-ethynylestradiol increased freezing and bottom-dwelling when fish were placed in a non-familiar aquarium, but did not significantly affect shoaling behaviour. These results are similar to the anxiogenic behaviours seen in rats treated perinatally with 17α-ethynylestradiol and add more concern to the impacts of endocrine disruptors on aquatic wildlife.