midterm-6-Differentiation-and-Gene

Chapter 10 - Differentiation and Gene Expression

Overview

The development of a plant organism is influenced by both genetic factors and the sequence of environmental experiences. The outcome of these interactions cannot be predicted solely from the DNA sequence.

10.1 Cellular Development and Coordination

Gene Expression and Cell Differentiation: The process of generating a plant cell requires the expression of numerous genes. Differentiation leads to various cell types with specific gene expression patterns.
Cell Division: Primary growth occurs in meristems, where cell division provides new cells for root and stem elongation. Factors like gamma irradiation affect cell division and plant height.
Cell Cycle: The cell cycle consists of G1 (gap), S (synthesis), G2 (gap), and M (mitosis) phases. Cyclin-dependent kinases (CDKs) regulate transitions between phases, influenced by plant hormones.
Cytoskeleton: The plant cytoskeleton, consisting of actin filaments and microtubules, plays critical roles in maintaining cell structure and facilitating plant cell communication.

10.2 Options for Differentiation

Totipotency: Many plant cells can regenerate into whole plants if they maintain intact genomes. This property allows for plant propagation and organ development.
Differentiation Types: Cells differentiate to form organized structures, like roots or shoots, influenced by growth regulators.

10.3 Gene Expression

Gene Regulation: Only a small part of the nuclear genome consists of functional genes, while most are non-coding or repetitive sequences. Gene expression is governed by a central dogma: DNA → RNA → Protein.
Transcription: mRNA synthesis involves the promoter, coding region, and terminator. Regulatory proteins help initiate transcription.
Post-initiation Control: mRNA can be influenced at various levels, including translation regulation and protein turnover.

10.4 Genetic Engineering in Plants

Transformation Systems: Introducing foreign DNA into plants uses Agrobacterium-mediated transformation or direct DNA uptake. Selection markers such as antibiotic resistance genes allow identification of transformed plants.
Transgenic Plants: Transgenic plants exhibit traits like herbicide resistance or pest resistance through engineered genes. Examples include Bt cotton, which expresses a bacterial toxin to kill specific pests.
Commercial Applications: Genetically modified crops may improve yield, enhance resistance to diseases, and increase shelf life of produce.
Ethical Considerations: The use of genetically engineered organisms raises concerns regarding biodiversity, ecological impacts, and health implications for consumers.