Self and Non-self in Reproductive Biology 1. Review of flower function -variation in flowers -flower...
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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
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 38.1 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
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
Angraecum sesquipedale
© Esko Puupponen Xanthopan
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
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
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
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.
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
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.