Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency

Self and Non-self in Reproductive Biology1. Review of flower function -variation in flowers -flower development2. Pollination Ecology -pollen efficiency -outcrossing3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility4. Selfing as a Way of Life

Figure 38.2 Review of an idealized flower

Figure 38.3a Trillium


Figure 38.1 Simplified overview of angiosperm life cycle

Figure 38.3ax2 Lily

Figure 38.4 The development of angiosperm gametophytes (pollen and embryo sacs)

Dispersed Pollen Grain

Generative Cell

Tube Cell

Pollen Coat

4 Microspores

Figure 38.5 Pollen grains have tough, ornate, and distinctive walls

Figure 38.3ax1 Lily

Cross Section of an Ovary

One ovule just after meiosis

Figure 38.4 The development of angiosperm gametophytes (pollen and embryo sacs)

Mature female gametophyte

Egg

Four-nuclear female gametophyte after two mitotic divisions of the megaspore)

Figure 38.9 Growth of the pollen tube and double fertilization

Figure 38.10 The development of a dicot plant embryo

http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookflowersII.html

Figure 30.17 The life cycle of an angiosperm


Angraecum sesquipedale

© Esko Puupponen Xanthopan


Three paths for pollen flow: selfing: 1. Within flower 2. Between flowers 3. outcrossing (between plants)

box elder: imperfect flowers, dioecious plants

Red Maple:imperfect flowers, dioecious plants

(usually…) staminatepistillate

Figure 38.3e

corn – imperfect flowers, monoecious plants

Foxgloves and outcrossing

Figure 38.3bx1 Foxglove

Female zone

Male zone

Bees fly up

Then start over at the bottom

Three components to outcrossing in foxglove1. Young flowers are male, old are female2. Young flowers are nearer the top3. Bees fly up.

primroses and heterostyly

syndromes


REVIEW SESSION FOR PARIS AND BARRINGTON SECTIONS

THURSDAY MAY 1, 5-6 PM, ROOM 235 MARSH LIFE SCI BLDG.

Darwin’s pollination experimentwith the primrose:

Ss ss -> Ss and ss in a 1:1 ratio

S s

s

s

Ss

Ss

ss

ss

Ss yields a short-styled flower.

Heterostyly is controlled by a gene S with simple inheritance:

ss yields a long-styled flower.

Illegitimate pollinations provide a test of the proposed genetic system…

S s

s

s

Ss

Ss

ss

ss

Ss (short-styled) flower ss (long-styled) flower.1:1short:long

S s

S

s

SS

Ss

Ss

ss

s s

s

s

ss

ss

ss

ss

Ss (short-styled) flower Ss (short-styled) flower.3:1 short:long

ss (long-styled) flower ss (long-styled) flower.all are long

http://www.biologie.uni-hamburg.de/b-online/e10/19.htm

Pollen and Stigma papilla size go with style length:

papillae

pollen

short-style form long-style form

http://www.biologie.uni-hamburg.de/b-online/e10/19.htm

Pollen and Stigma papilla size go with style length:

papillae

pollen

short-style long-style

pollen on stigma,legitimate unions

legitimate unionsin red

Gametophytic self-incompatibility continued:

Inhibition is through enzymes moving into pollen tube from style.

Evidence lies in a protein found in styles of petunias with incompatible pollen tubes, but not in those with compatible tubes -

Multiple alleles are found in species to allow a diverse definition of self---at least 75 in white clover and 150 in red clover.

Two kinds of self-incompatibility:1. Sporophytic (as in Primula):

S1S2 S1S3 does not yield inhibition of pollen Only the same two alleles yield inhibition

--- happens on the stigmainhibition is through preventing hydration of pollen on stigma

G - style length

Sp - stigma papilla length

I - self incompatibility(sporophytic)

P - pollen grain size

A - anther height

The Primula supergene:five genes linked together

that1. structurally improve

chances of legitimate pollination and

2. inhibit illegitimate pollen

Self and Non-self in Reproductive Biology1. Review of flower function -variation in flowers -flower development2. Pollination Ecology -precise placement -outcrossing3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility4. Selfing as a Way of Life

Two kinds of self-incompatibility:2. Gametophytic (as in Petunia):

Two kinds of self-incompatibility:Gametophytic (as in Petunia): S1S2 female S1S3 male yields inhibition of S1 pollen, not of S3 pollen --- happens in the style

Pollen tubes (with asterisks) growing in styles of a grape flower.

which marks the for destruction in the proteasomes (protein death chambers)

fails, allowing ubiquitin to be bound to pollen-tube proteins,

A ribonuclease

In incompatible interactions,

which degrades the pollen tube.


Violets have two kinds of flowers, one for outcrossing, one for selfing.

Selfing plants have little flowers, often without petals, and grow in disturbed terrain

chickweed

Closing Synthesis (roughly as presented in lecture):

Why bother with perfect flowers? As a backup; sessile organisms cannot move to find mates, so – especially in situations where pollinators are rare – selfing allows seed production, albeit with the limited genetic diversity possible with gametes from a single individual.

Violets, the next example, combine both worlds. Weed species such as chickweed have become dedicated to selfing, in the process purging themselves of deleterious alleles. This option yields short-term success but limited long-term evolutionary options. There are no large lineages of selfed plants.

Documents

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency