A Historical Journey through the science of ciliate mating types and conjugation

Metz et al 1948

Gor

tz e

t al 1

999

2006

It all started in 1937……..

• Tracy M Sonneborn

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…..with T. Sonneborn wanting to study sex in unicellular organisms & its relation with the ‘egg-sperm’ fusion

Sonneborn et al 1937

Ciliate mating types and Conjugation

Luporini et al 2005: Ciliate mating types and their protein pheromones Acta Protozool.

44: 89-101

Miyake Akio 1996: Fertilization and sexuality in ciliates: In Ciliates: cells as organisms

243-290

Metz 1948: The nature and mode of action of mating type substances The Am. Nat.

82(802): 85-95

Sujal PhadkePopulation Biology-Spring 07

Metz 1948: The nature and mode of action of mating type substances The Am. Nat.

82(802): 85-95

Questions addressed:1. How is a mating type inherited?

x non-x

Metz 1948: The nature and mode of action of mating type substances The Am. Nat.

82(802): 85-95

Questions addressed:2. What is the physiology and mechanism of conjugation?

Nuclear activity

Through the interaction between opposite mating types

3. What constitutes mating type ‘substances’ or ‘sex stuff’?

• Cell-bound (Ciliary origin)

• Complementary structures*

4. What is the effect of dead animals of opposite mating type?• Induction of nuclear rearrangements but within individual cells

(autogamy)

Conclusions:

I. Mechanism of conjugation induction: • Cell union (and nuclear rearrangements) as a result of interaction

between two opposite* mating types

II. The nature of complementary interaction:

Gamone-Receptor hypothesis

1. How is a mating type inherited?

Miyake Akio 1996: Fertilization and sexuality in ciliates: In Ciliates: cells as organisms

243-290

Induction of conjugation and autogamy:

I. Chemical induction- Ionic imbalance due to salts (Na, Al, Fe, Au) - DNA binding compounds: DAPI, Safranin O

II. Environmental induction*- Starvation

III. Developmental induction*- Clonal age- Interaction between opposite mating type

2. What is the physiology and mechanism of conjugation?

Induction of conjugation union in Blepharisma japonicum

Starvation Clonal age

Interaction between opposite mating type

Mating type I: Pheromone (G1)Mating type II: Pheromone (G2)

-Sugiura et al 2005

The model of induction in Blepharisma

3. What constitutes mating type ‘substances’ or ‘sex stuff’?

Luporini et al 2005: Ciliate mating types and their protein pheromones Acta Protozool.

44: 89-101

I. Blepharisma: Mating type I: Glycoprotein Mating type II: Non-peptide tryptophan derivative - Non-homologous mating types, different loci

II. Paramecium: Mating type I produces a precursor molecule of mating

type II

III. Euplotes*: Homologous mating types, single locus

Structural similarity in Euplotes mating type proteins- mutations in a single gene- 10-15% cysteine content; most cysteines are conserved- TGA codes for cysteine in Euplotes only

In conclusion……Why do people still study ciliate mating types?

1. Important in intra- and intercellular signaling system

2. Important in ciliate sex3. Important in speciation due to mating

incompatibility 4. Reassignments and conservation of stop codon(s)5. Very diverse in different ciliates