Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. Selfing as a Way of Life

Figure 38.2 Review of an idealized flower

Figure 38.3a Trillium

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. Selfing as a Way of Life

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 The development of a dicot plant embryo

Figure The life cycle of an angiosperm

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. Selfing as a Way of Life

Angraecum sesquipedale © Esko Puupponen Xanthopan

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. Selfing as a Way of Life

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…) staminate pistillate

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 foxglove 1. Young flowers are male, old are female 2. Young flowers are nearer the top 3. Bees fly up.

primroses and heterostyly

syndromes

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. Selfing as a Way of Life

REVIEW SESSION FOR PARIS AND BARRINGTON SECTIONS THURSDAY MAY 1, 5-6 PM, ROOM 235 MARSH LIFE SCI BLDG.

Darwin’s pollination experiment with the primrose:

Ss  ss -> Ss and ss in a 1:1 ratio S s s s 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… Ss s s Ss ss Ss (short-styled) flower  ss (long- styled) flower. 1:1short:long Ss S s SS Ss ss ss s s Ss (short-styled) flower  Ss (short-styled) flower. 3:1 short:long ss (long-styled) flower  ss (long- styled) flower. all are long

Pollen and Stigma papilla size go with style length: papillae pollen short-style form long-style form

Pollen and Stigma papilla size go with style length: papillae pollen short-style long-style pollen on stigma, legitimate unions in 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): S 1 S 2  S 1 S 3 does not yield inhibition of pollen Only the same two alleles yield inhibition --- happens on the stigma inhibition is through preventing hydration of pollen on stigma

G - style length S p - stigma papilla length I - self incompatibility (sporophytic) P - pollen grain size A - anther height The Primula supergene: five genes linked together that 1.structurally improve chances of legitimate pollination and 2.inhibit illegitimate pollen

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -precise placement -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. 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): S 1 S 2 female  S 1 S 3 male yields inhibition of S 1 pollen, not of S 3 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.

Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower development 2. Pollination Ecology -pollen efficiency -outcrossing 3. The Genetics of Outcrossing -maintaining heterostyly -self-incompatibility 4. Selfing as a Way of Life

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.