molecular mechanisms of the phenomena of self-incompatibility of plants

1. Molecular basis of
self-incompatibility

2. What is self-incompatibility?
Pollen produced reaches the stigma of a flower of the
same plant
The process of pollen germination is halted
(Buchanan, et al., 2005)
Source :-
http://www.akitarescueoftulsa.com/parts-of-a-carnation-flower-diagram/

3. Self-incompatibility -controlled by a single genetic
locus with multiple alleles, S locus. (Buchanan, et al.,
2005)
 S-RNase gene
 Pollen S-gene
 SLG (S-Locus Glycoprotein) gene
 SRK (S-Receptor Kinase) gene
 SCR (S-locus Cysteine-Rich protein) gene

4. Gametophytic self-incompatibility (GSI)
Sporophytic self-incompatibility (SSI)
(Buchanan, et al., 2005)

5. S-RNase–mediated degradation of pollen
tube RNA
SLF (S-Locus F-box) gene
 Pollen S-Locus-specific F-Box Protein
 3 S-RNase-Binding-Regulating Domains
(SBRD) FD1,FD2,FD3
 FD2- Binds with RNase
 FD1, FD3 - Determine S-allele-specificity of
SLF
 Weaken the strong interaction between FD2 of
SLF protein & S- RNase

6. S-Rnase gene
 Pistil-polymorphic glycoprotein
 Ribonuclease catalytic activity
 Allele-specific cytotoxin
(Hua, et al., 2008)

7. S-RNase–mediated degradation of pollen tube
RNA
(Takayama, et al., 2005)

8. (Takayama, et al., 2005).

9. S-protein–mediated signaling cascade in pollen
(Takayama, et al., 2005)

10. SCR (S-locus Cysteine-Rich) – In Pollen
Small, Basic, Cysteine-rich protein
S-locus Receptor Kinase (SRK)
S-Locus Glycoprotein (SLG) – In Pistil
ARC1 (Armadillo-Repeat-Containing 1)
Activated by Interacting with the cytoplasmic domain
of SRK

11. Stigmatic proteins - Ubiquitination & Proteasomal
degradation
Inhibition of pollen germination & pollen tube
elongation
Thioredoxin H-Like proteins (THL1 & THL2)
Interact with transmembrane domain of SRK protein
Inhibits auto phosphorylation activity of SRK
(Takayama, et al., 2005).

12. Receptor-kinase–mediated signaling in stigma
(Takayama, et al.,2005).

13. Inbreeding depression
Lower the population’s ability to survive and
reproduce
 Genetic variations - low
 Revolution process - low
 Recessive alleles - expressed
Prevented by Self-Incompatibility
(Igic, et al., 2008)

14. Reference:-
Buchanan, B. B. Gruissem, W. Jones, L.R. 2005. Biochemistry & molecular biology of
plants, 6th edition. Courier Companies, Inc., U.S.A, pp. 1018-1022.
Igic, B. Lande, R. Kohn, J.R. 2008, Loss of Self‐Incompatibility and Its Evolutionary
Consequences, “International Journal of Plant Sciences”, 169: 93-104.
Hua, H. Z. Fields, A. Kao, H. T. 2008, Biochemical Models For S-RNase-Based Self-
Incompatibility, “ Molecular Plant”, 1: 575-585.
Takayama, T. Isogai, A. 2005, Self-Incompatibility in Plants, “Annual Review of Plant
Biology”, 56: 467-489.
http://www.nature.com/nature/journal/v367/n6463/abs/367563a0.html(05.11.2015).
http://www.plantcell.org/content/14/suppl_1/S227/F2.expansion.html (05.11.2015).
http://www.akitarescueoftulsa.com/parts-of-a-carnation-flower-diagram/ (05.11.2015).