The expression of chloramphenical acetyl transferase (CAT) protein driven by the wound-inducible promoter from the proteinase inhibitor 11 K (pin2) gene was examined in whole tobacco (Nicotiana tabacum L.) plants under field conditions. Mechanical wounding of the field-grown leaves caused an accumulation of CAT protein in these leaves which begins several hours after wounding and continues to accumulate for about 36 hours. When sections of leaves were assayed for accumulation of CAT protein following wounding, the CAT protein was found to accumulate in the apical portions of the leaves. When endogenous insects attacked the leaves of transgenic plants grown in the field, the plants responded by inducing CAT protein. The mesophyll cells of the leaf were the site of expression of the CAT protein rather than the mid-vein or major veins within the leaf blade, indicating that the wound-inducible pin2 promoter specifically directs the synthesis of novel genes in tissues preferentially consumed by larval insects.are then free to act on their substrates, the plants' cell walls, to release small mol wt oligosaccharides (1,2,16). These oligosaccharides have been termed PIIF2. They are believed to be the signal which interacts with unwounded cells in an as yet undetermined manner to induce the de novo synthesis of proteinase inhibitor mRNA and protein (9). These genes have been used in whole plants to express the native inhibitors (17) or foreign proteins (18) One particular biochemical defense system utilized by plants against insects is directed against the digestive enzymes located in the insect gut. This system of proteinase inhibitors occurs in the seeds of almost all plant species ( 11) and in the foliage of solanaceous (potatoes and tomatoes) (10, 14) and leguminous (alfalfa) (6) plants.In response to insect attack, tomatoes and potatoes activate quiescent genes, which leads to the accumulation of at least two small protein families. The activation of these genes is complex and incompletely understood. Initially, wounding disrupts cells and specific enzymes, polygalacturonases, are released to the extracellular milieu. These polygalacturonases 'This work was supported by grants from the U.S. Department of Agriculture (87-CRCR-1-2518), the State of Iowa, and the Iowa Biotechnology Council. PlantsTobacco (Nicotiana tabacum L., cv Xanthi) plants transformed with a chimeric pin2-CA T construction were previously described (18). One line, Tr25, showed high levels of wound-inducible CAT activity and was chosen for further analysis. This line was made homozygous by self-fertilizing the plants. Selfed progeny in the R1 and R2 generations of Tr25 were grown on Murashige-Skoog (13) solid medium containing 200 gg/ml kanamycin. Since the pin2-CA T gene fusion is physically linked to a dominant kanamycin selectable marker (only 2.7 kb separates these genes), a test for a kanamycin resistance provides a good measure of the presence of the linked pin2-CA T gene. The R1 progeny segregated in a 3:1 ratio, indicating that the...
Since reading and writing digitally demand partially different competencies, there is a change in some of the premises of related educational practices. This study aims to contribute to the knowledge of educational reading practices by scrutinizing how literacy events evolve in a digital classroom where each student has a personal digital device (1:1), iPads in this study. Our study is grounded in sociocultural theories of learning and focuses on the structuring resources utilized by students, namely the notion of multiple ongoing activities and the ways in which specific resources take precedence in shaping these activities. One class of 13-14 year-old students was studied for a week across several subjects through video-recordings and observations. The findings imply that the students moved among vast array of reading practices. However, the main structuring resource is a strong focus on task-solving and the practice of schooling, which mainly builds on principles emanating from traditional text. It is only occasionally that structuring resources that also include the opportunities associated with digital technology are utilized. This indicates the importance of further studies on how educational practices could be organized to scaffold the basis of traditional reading comprehension as well as other approaches required in digital environments.
The purpose of this article is to explore how aspects of students' critical digital literacy can be developed through the analysis of digital multimodal texts in a secondary school classroom. The analysis of students' group discussions, when deconstructing a video clip, shows that opportunities to develop a critical awareness of prominent perspectives in a digital multimodal text increase when students become aware of the construction of the text. However, more instructional attention needs to be given to the role modes play across diverse elements in a digital multimodal text.
Due to the recent decades of rapid digitalization digital multimodal texts have become increasingly common. Almost anyone can also produce, edit and publish texts which have resulted in an increasing necessity for critical literacy in order to handle texts in digital domains. The purpose of this article is to explore how students’ critical literacy can be developed through in situ classroom activities. Grounding the study in sociocultural theories of learning and the concept of critical literacy, a design research approach was adopted, and an intervention was jointly designed by the researcher and the teachers. In focus was a class of 14-15-year-olds who were involved in activities of deconstructing a video clip from a popular teenage online series. Through interaction analysis of the classroom observations, it became evident that, by means of a step by step lesson structure, opportunities arise for increasing students’ awareness of how modes function concurrently and carry both separate and interconnected meanings. Through this process, students also discovered that different modes can be contradictory, enabling enhanced critical analysis in their making meaning of the text.
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