Gene introduction approaches in chloroplast transformation and its applications

Background Chloroplast is a type of plastid that is believed to be originated from ancestral cyanobacteria. Chloroplast besides being a major component for photosynthesis, also takes part in another major plant metabolism, making it one of the major components of plants. Main body Chloroplast transformation is an alternative and better genetic engineering approach compared to the nuclear transformation that has been widely applied in plant genetic engineering. Chloroplast transformation has exhibited various positive effects as compared to nuclear transformation. This is a more preferred technique by researchers. To carry out chloroplast transformation, the vector design must be performed, and a selectable marker needs to be incorporated before the chloroplast could uptake the construct. The common way of introducing a gene into the host, which is the chloroplast, involves the biolistic, PEG-mediated, carbon nanotubes carriers, UV-laser microbeam, and Agrobacterium-mediated transformation approaches. Apart from discussing the processes involved in introducing the gene into the chloroplast, this review also focuses on the various applications brought about by chloroplast transformation, particularly in the field of agriculture and environmental science. Conclusion Chloroplast transformation has shown a lot of advantages and proven to be a better alternative compared to nuclear genome transformation. Further studies must be conducted to uncover new knowledge regarding chloroplast transformation as well as to discover its additional applications in the fields of biotechnology.

Force balances between interphase centrosomes as revealed by laser ablation

Numerous studies have highlighted the self-centering activities of individual microtubule (MT) arrays in animal cells, but relatively few works address the behavior of multiple arrays that coexist in a common cytoplasm. In multinucleated Dictyostelium discoideum cells, each centrosome organizes a radial MT network, and these networks remain separate from one another. This feature offers an opportunity to reveal the mechanism(s) responsible for the positioning of multiple centrosomes. Using a laser microbeam to eliminate one of the two centrosomes in binucleate cells, we show that the unaltered array is rapidly repositioned at the cell center. This result demonstrates that each MT array is constantly subject to centering forces and infers a mechanism to balance the positions of multiple arrays. Our results address the limited actions of three kinesins and a cross-linking MAP that are known to have effects in maintaining MT organization and suggest a simple means used to keep the arrays separated.

Direct kinetochore–spindle pole connections are not required for chromosome segregation

Segregation of genetic material occurs when chromosomes move to opposite spindle poles during mitosis. This movement depends on K-fibers, specialized microtubule (MT) bundles attached to the chromosomes′ kinetochores. A long-standing assumption is that continuous K-fibers connect every kinetochore to a spindle pole and the force for chromosome movement is produced at the kinetochore and coupled with MT depolymerization. However, we found that chromosomes still maintained their position at the spindle equator during metaphase and segregated properly during anaphase when one of their K-fibers was severed near the kinetochore with a laser microbeam. We also found that, in normal fully assembled spindles, K-fibers of some chromosomes did not extend to the spindle pole. These K-fibers connected to adjacent K-fibers and/or nonkinetochore MTs. Poleward movement of chromosomes with short K-fibers was uncoupled from MT depolymerization at the kinetochore. Instead, these chromosomes moved by dynein-mediated transport of the entire K-fiber/kinetochore assembly. Thus, at least two distinct parallel mechanisms drive chromosome segregation in mammalian cells.