Molecular basis of self-incompatibility

What is self-incompatibility?Pollen produced reaches the stigma of a flower of the same plantThe process of pollen germination is halted(Buchanan, et al., 2005)

Source :-http://www.akitarescueoftulsa.com/parts-of-a-carnation-flower-diagram/

S locusSelf-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

Gametophytic self-incompatibility (GSI)

Sporophytic self-incompatibility (SSI)

(Buchanan, et al., 2005)

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

S-Rnase gene

Pistil-polymorphic glycoprotein Ribonuclease catalytic activity Allele-specific cytotoxin

(Hua, et al., 2008)

S-RNase–mediated degradation of pollen tube RNA

(Takayama, et al., 2005)

S-protein–mediated signaling cascade

• S gene in S-locus - Female determinant • S-proteins - Small, Secreted proteins

• Ca2+ influx to pollen tube shank • Loss of the apical gradient of Ca2+

• Inorganic pyrophosphatase • Inhibitor - calcium-dependent protein kinase

(CDPK)

(Takayama, et al., 2005).

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

Receptor-kinase–mediated signaling in stigmaSCR (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

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).

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

Inbreeding depressionLower 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)

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).

Thank you