Monitoring cell cycle modulated gene expression in plants by means of a whole-genome-based approach
Year: 2002
Type: dissertation
Abstract: Living beings are in a constant need to propagate the cells they are consisting of.In essence, cells reproduce in a cyclic mode by duplicating their contents and a subsequent division into two parts.Therefore, it is not exagerated to proclaim this cell division cycle to represent a fundamental aspect of life.In unicellular organisms, such as bacteria and yeast, the propagation procedure leads to the production of an additional entity.For multicellular species, many cells are needed to make up a new individual and even in the adult body, cell division is required to replace the cells that are lost by tear and wear or by more complex reactions such as progammed cell death.For instance, an adult human has to manufacture many millions of new cells every second, simply to maintain the status quo and if this for some reason becomes halted, the individual will die within a few days.The details of a cell cycle may vary for a certain species, but some requirements are considered to be universal in order to achieve the production of a pair of genetically identical daughter cells.First and foremost, the DNA has to be faithfully replicated and the replicated chromosomes have to become equally segregated into the resulting cells.Of equivalent importance is the problem to coordinate these events during the cell division process.Therefore, the existence of an adequately operating control system is compulsory.This chapter is concerned with the processes obligatory for proper cell division and the different ways they are coordinated with one another.After an introductory outline of the discrete phases, which make up a complete cell cycle, we will go into detail about the complex organization to control the right follow up of these events as well as the action of different extra cellular signals to direct cell cycle progress.Thorough research taught us that the proteins making up the control system first appeared over a billion years ago and have been well conserved during evolution.Consequently, one can consider the cell cycle to be highly preserved among eukaryotic species.For this reason, the decision was made to integrate the knowledge of yeast genetics together with studies on mammals and plants to draw a general picture of the status in molecular-genetic cell cycle research nowadays.Eukaryotes possess a large, complex network of linear polymers that serves as a roadway and scaffold for the contraction and motility of their cells, as well as the intracellular organization of the cytoplasm, organelle integrity and the movement of cargo within the cell.This set of connections is commonly referred to as the Figure 4: Transient formation of the preprophase band (PPB) during assembly of the plant mitotic spindle (A-D) Development of PPB (E-H) The prophase spindle forms from foci of micotubules at either end of the nucleus (G,H) Disassembly of PPB in late prophase (I-K) Formation of the mitotic spindle after breakdown of the nuclear envelope.Kinetochores capture bundles of spindle microtubules (A) (B) Figure 6: Cytokinesis in plant cells by formati on of the phragmoplast (panel (A)-right and (B)).This structure will reach the parental cell wall to build a new cell wall between the daughter cells.It consists mainly of actin filaments and microtubules A. Extracts taken from mitotic oocytes contain proteins that induce G2 cells to undergo mitosis.This and similar experiments were used to isolate a mitosis-promoting factor (MPF) capable of inducing G2 cells to divide B. Biochemical analyses of fractions of cell extract taken at various stages of the cell cycle reveal the presence of cyclins.Cyclin abundance correlates with the activity of MPF C. The two key subunits of MPF 1.2.1.2Post-translational modifications are essential for CDK/cyclin activityAs outlined earlier in the text, the most important aspect of cell cycle regulation is the association of a CDK with its cyclin partner.Hence, the periodic availability of cyclins as a 1.2.2.1.1.Progress through G1/S: The decision to divide once again Eukaryotic cells have evolved complex regulatory mechanisms in order to obtain an adequate interpretation of the cues governing their decision to divide or to differentiate.Ultimately, the gathered information will become translated to the basic cell cycle machinery, which is reviewed in this section.In unicellular eukaryotes, the molecules involved are different from those in multicellular organisms.Therefore, the discussion will be restricted to animal and plant cells that share a conserved mechanism for G1 progression and G1/S transition (Meijer and Murray, 2000;Durfee et al., 2000).
Author: Rozemarijn Dreesen
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2336019634