Transcript 슬라이드 1
- Chalcone synthase
- Antisense RNA approach
- Suppression observed with a sense
gene introduced
Fig. 1 Generalized pathway leading to
anthocyanidin 3-glucosides (Holton and
Cornish 1995). Anthocyanins of non-blue
flowers (rose, chrysanthemum and carnation)
and blue flowers (gentian and petunia) are
also shown. Blue flowers usually have
delphinidin modified with one or more
aromatic acyl group(s) such as caffeic acid
(Caf) and coumaric acid. PAL, phenylalanine
ammonia-lyase; C4H, cinnamate4hydroxylase; 4CL, 4-coumarate:CoA ligase;
CHS, chalcone synthase; CHI, chalcone
isomerase; F3H, flavanone 3-hydroxylase;
Fill, flavonoid-3'-hydroxylase; F3'5"H,
flavonoid 3\5'-hydroxylase; DFR,
dihydroflavonol 4-reductase; ANS,
anthocyanidin synthase;
3GT, flavonoid 3-glucosyl transferase; CC3H,
4-coumaroyl-CoA 3-hydroxylase; FNS,
flavone synthase; FLS, flavonol synthase;
Glc, glucose; Rha, rhamnose.
Figure 1. Phenotypes of Chimeric CHS Transgenotes and Variations among Flowers on Single Plants.
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Dr. R. Goldberg (UCLA) and Plant Genetic Systems
Male Sterility
TA29, TA13 genes
Tapetum-specific promoters
RNase gene (Barnase)
Barstar inactivates Barnase
Pollenless
Identity (동질성) vs. Variety (다양성)
-Dioecy, poplar
-Monoecy, corn
-Heteromorphic flower, flax
-Homomorphic flower : SSI, GSI
Sporophytic Self-Incompatibility (SSI)
Brassica, turnips, rape,
cabbage, broccoli, and
cauliflower.
In this SSI system,
•Rejection of self pollen is controlled by the diploid genotype of
the sporophyte generation.
•The control lies in the "S-locus", which is actually a cluster of
three tightly-linked loci:
•SLG (S-Locus Glycoprotein) which encodes part of a receptor
present in the cell wall of the stigma;
•SRK (S-Receptor Kinase), which encodes the other part of
the receptor. Kinases attach phosphate groups to other
proteins. SRK is transmembrane protein embedded in the
plasma membrane of the stigma cell.
•SCR (S-locus Cysteine-Rich protein), which encodes a
soluble, secreted ligand for the same receptor.
•Because the plants cannot fertilize themselves, they tend to be
heterozygous; that is, carry a pair of different S loci (here
designated S1 and S2).
However, dozens of different S alleles may be
present in the population of the species; that is; the
S-locus in the species is extremely polymorphic
(analogous to the major histocompatibility locus of
vertebrates — Link).
The difference between the alleles is concentrated
in certain "hypervariable regions" of the receptor
(analogous to the hypervariable regions that provide
the great binding diversity of antibodies — Link).
The rules:
Pollen will not germinate on the stigma (diploid) of a flower
that contains either of the two alleles in the sporophyte
parent that produced the pollen.
This holds true even though each pollen grain — being
haploid — contains only one of the alleles.
In the example shown here, the S2 pollen, which was
produced by a S1S2 parent, cannot germinate on an S1S3
stigma.
Gametophytic Self-Incompatibility (GSI)
Solanaceae, potatoes, tomatoes,
and tobacco
beets (Beta vulgaris)
buttercups (Ranunculus)
lilies
roses
many grasses
This appears to be the mechanism in tobacco:
All pollen grains — incompatible as well as compatible — germinate
forming pollen tubes that begin to grow down the style.
However, growth of incompatible pollen tubes stops in the style while
compatible tubes go on to fertilize the egg in the ovary.
The block within incompatible pollen tubes is created by an S-locusencoded ribonuclease (RNase), which is synthesized within the style;
enters the pollen tube and destroys its RNA molecules
halting pollen tube growth.
The RNase molecules contain a hypervariable region
which is the basis for each S specificity (S1, S2, S3, etc.).
The pollen tube expresses a molecule that binds RNase.
This targeting molecule also exists is different S
specificities (S1, S2, S3, etc.).
In compatible ("nonself") tubes, the targeting molecule
sequesters the RNase in a vacuole thus permitting RNAs in
the cytosol to survive and growth to continue.
In incompatible ("self") tubes the binding of, for example,
the S1 targeting molecule to an S1 binding site on the S1
RNase releases the RNase into the cytosol so the RNAs of
the pollen tube are destroyed and growth is halted.
Other mechanisms may be used by other species with
gametophytic self-incompatibility.