,
,-1- Plant genomes
There are 3 types of genomes in plant cells:
• Chloroplast genome = circular, double stranded DNA that ranges from 120 to 160 kb in
size and contains about 120-140 genes. If there are inverted repeats it is type II
chloroplast genome.
• Mitochondrial genome = 200 – 2500 kb and thus much larger than mammals. Lots of
non- coding DNA, few genes. Promiscuous DNA = chloroplast DNA in mitochondrial DNA
• Nuclear genome = DNA/chromosomes in cell Nucleus
DNA -> histones -> nucleosomes(DNA 150bp wrapped around histones, cores H2A, H2B, H3 and H4)
-> 30nm fibre -> wrapped into chromosomes
microRNA = short (21-24 nucleotides) RNAs that are found in the genome regions that are not
associated with protein-coding genes. They are generally well conserved among plant species.
First a hairpin needs to be synthetized from the miRNA. These
are produced by RNA polymerase II, like normal RNA. Dicer, a
RNAse III endonucleoase, splices the duplex into mature
miRNA which is also referred to as RNA induced silencing
complex (RISC). Not shown in picture, RISC also has an
Argonaut molecule (AGO1) attached.
In translation of a gene, transcription factors (TFIID) bind to
the TATA-box. These transcription factors then attract RNA-
polymerase II and the gene is activated.
Ribosomes attach to the 5’ side of the mRNA and move one
codon in the 3’ direction.
Gene expression can be influenced by:
• Chromatin conformation (eu- and heterochromatin, open and closed), also including
DNA methylation
• Gene transcription (promotor, cis-elements = sequence elements that function to recruit
the proteins that regulate transcription of a gene located on the same DNA-strand as the
coding region for the gene, transcription factors)
• RNA modification (splicing, alternative splicing = combining exons in different ways)
• Translation
• Post translational modification (phosphorylation, glycosylation and acetylation)
• Localization (protein needs to be transported to compatible location)
• Protein turnover
Essential are promotor cis elements and a poly A signal.
Alternative splicing = combining exons differently to obtain different proteins from the same gene.
Promotor analysis = determining how long the upstream promotor sequence is by testing various
promotor gene fusions. The moment that the gene product is not produced anymore determines
how long the promotor fragment is.
, promotor examples:
• Light regulated gene expression using light-responsive elements (LREs)
• Abscisic acid-induced gene expression ABA
• Tissue specific expression
-2- Plant tissue culture
Plant cells are totipotent = each individual plant cell can under right circumstances develop into a full
plant.
Plant hormones:
1- Auxin => promotes cell division
2- Cytokinin => promotes cell division
3- Gibberellin => cell elongation, germination
4- Abscisic acid (ABA) => inhibits cell division
5- Ethylene =>
ripening Auxin:
• Natural: IAA
• Synthetic: IBA, NAA, 2,4-D (most commonly used because very
stable) cytokinin:
• natural: Zeatin, 2iP ((N6-(2-isopentyl)adenine)
• synthetic: kinetin, BAP (6-benzylaminopurine)
auxin = cytokinin -> callus formation
auxin < cytokinin -> shoot formation
auxin > cytokinin -> root formation
,-1- Plant genomes
There are 3 types of genomes in plant cells:
• Chloroplast genome = circular, double stranded DNA that ranges from 120 to 160 kb in
size and contains about 120-140 genes. If there are inverted repeats it is type II
chloroplast genome.
• Mitochondrial genome = 200 – 2500 kb and thus much larger than mammals. Lots of
non- coding DNA, few genes. Promiscuous DNA = chloroplast DNA in mitochondrial DNA
• Nuclear genome = DNA/chromosomes in cell Nucleus
DNA -> histones -> nucleosomes(DNA 150bp wrapped around histones, cores H2A, H2B, H3 and H4)
-> 30nm fibre -> wrapped into chromosomes
microRNA = short (21-24 nucleotides) RNAs that are found in the genome regions that are not
associated with protein-coding genes. They are generally well conserved among plant species.
First a hairpin needs to be synthetized from the miRNA. These
are produced by RNA polymerase II, like normal RNA. Dicer, a
RNAse III endonucleoase, splices the duplex into mature
miRNA which is also referred to as RNA induced silencing
complex (RISC). Not shown in picture, RISC also has an
Argonaut molecule (AGO1) attached.
In translation of a gene, transcription factors (TFIID) bind to
the TATA-box. These transcription factors then attract RNA-
polymerase II and the gene is activated.
Ribosomes attach to the 5’ side of the mRNA and move one
codon in the 3’ direction.
Gene expression can be influenced by:
• Chromatin conformation (eu- and heterochromatin, open and closed), also including
DNA methylation
• Gene transcription (promotor, cis-elements = sequence elements that function to recruit
the proteins that regulate transcription of a gene located on the same DNA-strand as the
coding region for the gene, transcription factors)
• RNA modification (splicing, alternative splicing = combining exons in different ways)
• Translation
• Post translational modification (phosphorylation, glycosylation and acetylation)
• Localization (protein needs to be transported to compatible location)
• Protein turnover
Essential are promotor cis elements and a poly A signal.
Alternative splicing = combining exons differently to obtain different proteins from the same gene.
Promotor analysis = determining how long the upstream promotor sequence is by testing various
promotor gene fusions. The moment that the gene product is not produced anymore determines
how long the promotor fragment is.
, promotor examples:
• Light regulated gene expression using light-responsive elements (LREs)
• Abscisic acid-induced gene expression ABA
• Tissue specific expression
-2- Plant tissue culture
Plant cells are totipotent = each individual plant cell can under right circumstances develop into a full
plant.
Plant hormones:
1- Auxin => promotes cell division
2- Cytokinin => promotes cell division
3- Gibberellin => cell elongation, germination
4- Abscisic acid (ABA) => inhibits cell division
5- Ethylene =>
ripening Auxin:
• Natural: IAA
• Synthetic: IBA, NAA, 2,4-D (most commonly used because very
stable) cytokinin:
• natural: Zeatin, 2iP ((N6-(2-isopentyl)adenine)
• synthetic: kinetin, BAP (6-benzylaminopurine)
auxin = cytokinin -> callus formation
auxin < cytokinin -> shoot formation
auxin > cytokinin -> root formation
