Engineering Plants

Engineering Plants

Expressing Genes

Genotype+Epigenetic Interactions(E.I)+Environment = Phenotype

• E.I = even if a gene is in a genome it might not be expressed 

  • Epigenetic control= configuration of the genome DNA to allow or block access to original template

    • It is mothballed in a way that mrnapol can’t get to it

• Environment = includes human interactions like pruning

• Genes can only be used so far

Levels of Control

• Epigenetic control= configuration of the genome DNA to allow or block access to original template

  • It is mothballed in a way that mRNA polymerase can’t get to it

• Transcriptional regulation: control of transcription initiation, maintenance of transcription, and termination

• Posttranscriptional regulation: control of mRNA stability, translation efficiency, and degradtion

  • Rnapol can get in there and do its thing but then the transcription gets shredded/ broken/ is done inefficiently

  • Still making the message but making it wrong

• Protein stability : determines activity/ efficiency of the product

  • Maybe we don’t change epigenetic control and we let the protein of interest be made but then we introduce another so that it is broken or soemthing

• When we talk about expression we are talking about what the final protein is gonna do

• We are gonna focus on the transcription and processing steps

  • RNA Polymerase is like crazy important

    • Rna polymerase II is the main transcribing one

    • Needs a transcription factor to kickstart the transcribing process

    • Genes that will be expressed have to available for rna polymerase to access

• The things we can manipulate are genes

  • If you can control a gene by cutting or sending stop signals you can change what the result is

    • Any gene that is coding for a protein will have a promoter that has two parts it's what signals mrnapoly to start

      • core/minimum promoter

      • Regulatory promoter

    • Surpressors do the opposite and cover up the start site 

  • Introns are the main difference

    • Introns get taken out in the transcribed section

  • Codes are buried in the original genomic dna that tell rnapol to transcribe or leave alone

  • There are pieces embedded in the genome that aren’t a part of the protein when it is made that control how much of and when to make all the proteins

    • The transcription unit: where the rnapol sits down

    • Cis-acting control elements: adjactent to the transcription

    • Trans-acting factors: encode transcription factors/proteins encoded elsewhere in the genome

• NOT ALL GENES CODE FOR PROTEINS AND NOT ALL DNA IS GENES

• Traditional plant breeding

  • We look at what is being expressed and then look at the genomic dna to see if those traits will be inheritable

GE crops

• Technically selective breeding is ge but what most people mean is when some gene from another organism is introduced to the genome of a different plant 

RNAi

Posttranscriptional Control

• Rnai has a protein that they are looking for and then find it and remove it

Agrobacterium tumefaciens

• First ge plant made possible bc of this natural occurring bacteria that is everywhere

• We figured out that galls on trees that form when injury happens occur bc of agrobacterium! We figured that out and used it to do our bidding basically> roundup ready corn

  • THANK YOU MARY DELL CHILTON, PhD

• Used plasmid rings

  • Random insertion that you can’t control

  • Put antibiotic resistance markers on the sequence you want to insert so you can tell WHERE it successfully lived

Gene gun

• Can we use the plasmid ring but like control where it goes??

• YES! You have to kinda hope and pray that it works and do it a whole lot to get one that works

  • Still probably using the antibiotic resistant gene

Targeted Modifications

• Targeted mutagenesis by sequence-specific nucleases 

  • Thats what CRISPR is

• Precise gene replacements, base editing, and prime editing

  • This is what people are developing now

  • It is much more direct like you can go specifically 

CRISPR-Cas

• Targeted way to change the way we modify genes

  • Taking snapshot of memory of DNA (from that of an infecting phage originally discovered because of this)

  • The CAS 9 protein goes in and cuts the genome

Regulation shift?

Takes about 10 years to get something GE approved through the FDA

• New approach is being introduced from GE scientists

  • GE needs to be regulated like how other breeding plants are bc we’re doing the same kind of modification

Marker-Assisted breeding

• Molecular breeding is an alternative to genetic modification

  • Focuses on mutants that already exist that have properties we want

  • Have to have a sequenced genome

• You breed the plants in a traditional way but look at the genes to see how your genes are being transferred

• Get be approved without neeeear as much regulation as ge even though you can get similar results yippee!