chapt 10- Recombinant DNA Technology, Plant Biotechnology & Genomics

Why are Arabidopsis and rice popular models for angiosperm genetics?

• compact genome that is fully sequenced

• short life cycle, rapid experimentation

• easy to grow

• many mutant libraries

• represent dicots

rice:

• important food crop

• relatively small genome that is fully sequenced (reference for other cereal crops)

• monocot representation

How is Agrobacterium used to transform plants?

• natural ability to transfer DNA into plant cells

• contains Ti plasmid that carries segment T-DNA (modified to include genes of interest for plant transformation)

• infects plants by attaching to wounded plants and transfer the T-DNA into plant’s genome

• T-DNA integrates into plant genome

What are some examples of widely used transgenes for herbicide resistance and herbicide resistance?  For other traits?

glyphosate resistance (EPSPS gene) from agrobacterium tumefaciens introduced to crops like soybeans, corn, and cotton to confer resistance to glyphosate

glufosinate resistance (bar or pat gene) from streptomyces species provides resistance to glufosinate herbicides

Bt gene from bacillus thuriniensis produces protein toxic to specific insect pests, used in cotton and corn

Rps in soybeans protect against fungal pathogens

DREB (dehydration-responsive element-binding protein) enhance a plant's ability to withstand water scarcity

Golden Rice project uses genes from daffodils and bacteria to produce beta-carotene, a precursor to vitamin A, in rice

Flavr Savr tomato uses an antisense gene to slow down the softening process, extending shelf life

What are some of the benefits and risks of genetically modified crops?

benefits:

• increase yield

• reduced pesticide use

• enhanced nutritional content

• drought/salinity tolerance

• longer shelf life

risks:

• environmental impact-potentially lead to dominance of certain species and decline of others

• gene flow (cross pollination)

• resistance development (pests and weeds may evolve to have resistance)

• health concerns

Vocabulary: hydroponics, totipotency, synteny

hydroponics: method of growing plants without soil, using nutrient-enriched water or an inert medium like sand, gravel, or perlite to support the plants

totipotency: ability of a single plant cell to regenerate and develop into an entire plant under the right conditions

synteny: conservation of gene order and content across chromosomes within or between species