slide1
Download
Skip this Video
Download Presentation
Sexual reproduction

Loading in 2 Seconds...

play fullscreen
1 / 55

Sexual reproduction - PowerPoint PPT Presentation


  • 128 Views
  • Uploaded on

Sexual reproduction. Thomas Geburek Department of Genetics Federal Research Centre for Forests, Natural Hazards, and Landscape (BFW) Austria. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia. Recall: The main source of genetic variation is recombination!.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Sexual reproduction' - bobby


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Sexual reproduction

Thomas Geburek

Department of Genetics

Federal Research Centre for Forests, Natural Hazards,

and Landscape (BFW)

Austria

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide2

Recall:

The main source of genetic variation is recombination!

Sexual reproduction is a very important component of the genetic system that

stores,

transmits,

creates,

tests

genetic variation.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide3

Sexual Systems

Dioecious: all trees are either male or female

Ginkgo biloba (male)

Ginkgo biloba (female)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide4

Sexual Systems

Dioecious: all trees are either male or female

Hermaphrodite: individual tree with both male and female functioning flowers. It may have either monoecious flowers (single sex flowers  monoecy) or hermaphrodite (=bisexual) flowers.

Monoecious: hermaphrodite tree in which male and female gametes are produced in separated flowers (bisexual)  sex function

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide5

Sexual Systems

Example: Mahagony (Swietenia spec.)

Morphology  hermaphrodite flowers

Functions  monoecious flowers, because anthers or ovaries are vestigial

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide6

red manjack

(Cordia collococca)

Flowers are clearly hermaphrodite, but sex function varies considerably.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide7

Monoecious trees are found

approx. 75 % in boreal and temperate zones

approx. 10 % in tropical zones.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide8

Sexual Function

Sexual function refers to the frequency of the effective sexual types.

Bisexuality does not mean that trees function equally as females or males.

In monoecy, the sexual function (S) may be estimated by the number of effective female gametes vs. total number of effective gametes.

S varies from zero (exclusively males) to one (exclusively females)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide9

Si = N ♀ i /(N ♀i + N ♂i )

Effective number (N) of gametes can only be roughly estimated. If pollen is in surplus, census (C) ♀ can be regarded as effective.

N♂i= (C ♂i /C ♂)C ♀

Si = C ♀i x C ♂/ (C ♀i x C ♂ + C ♀iC ♀)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide10

Malaysian example

Garciniascortechinii tended towards femalenees in a censused 25 ha area in the Pasoh Forest Reserve (West Malaysia). No males recorded, however 68 % of the adult trees fruited(Thomas 1997).

Sexual function S = 1.0

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide11

0

1.0

0.5

Sexual Function and Structure

1.0

Relative Proportion

0.5

Sexual function

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide12

Dioecy excludes self-pollination thus reduces coancestry among offspring.

In bisexual plants coancestry is reduced by

  • incompatibility systems,
  • avoidance of self-pollination by spatial separation of males and female stroboli.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide14

Dioecy excludes self-pollination thus reduces coancestry among offspring.

In bisexual plants coancestry is also reduced by

  • incompatibility systems,
  • avoidance of self-pollination by spatial separation of males and female stroboli,
  • temporal separation of the flowers (protogyny or protandry)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide15

Incompatability Systems

homomorphic gametophytic self-incompatibility

Gene product are ribonucleases (S-RNA-ases) expressed in the pistil constituting a barrier for certain pollen tubes.

S-RNA-ase encoded by the same S-allele (from the maternal tree) reacts with the cytoplasm of the pollen carrying the same S-allele through enzymatic degradation of the r-RNA of the pollen tube.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide16

(1) Homomorphic gametophytic self-incompatibility

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide17

Consequences:

Prevents selfing and mating with closely related trees.

Number of incompatability alleles determines number of possible crosses.

Example: Leucaema diversifolia

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide19

Incompatability Systems

homomorphic sporophytic self-incompatibility

Diploid genome of the pollen grain reacts with the diploid tissue of the receptive plant.

Sharing of only one incompatibility allele between prospective mates prevents reproduction success.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide20

(1) Homomorphic sporophytic self-incompatibility

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide21

Consequences:

Prevents selfing and mating with trees sharing only one incompatability allele.

Number of incompatability alleles determines number of possible crosses.

Example: Ulmus

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide22

Heteromorphic sporophytic self-incompatibility

Heterostyly

ss Ss

ss no yes

Ss yes no

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide23

Example: Cordia alliodora

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide25

Papaya (Carica papaya)

  • fruit tree
  • indigeneous to the American tropics
  • dioecious

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide27

Female (pistillate) tree– functional ovary , no stamens, pollination from separate trees – genotype mm

Male (staminate) tree – no ovary, only stamens – genotype M1m

Hermaphroditic tree – low temperature gives a shift to femaleness, high temperature gives a shift to maleness - genotype M2m

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide28

Possible crosses

mm (pistillate) x M1m (staminate)

 1 mm : 1 M1m

M2m (hermaphroditic) x M2m (hermaphroditic)

 1 M2M2 (lethal) : 2 M2m : 1 mm (pistillate)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide29

Incompatability Systems

post-zygotic

  • Conifers have no pre-zygotic incompatibility system.
  • Embryonic abortion due to early acting inbreeding
  • lethal recessive mutants

embryonic lethal equivalents or embryonic lethals

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide30

Embryonic lethals

  • Different models
  • Number can be estimated by

Embryonic lethals =

- 4 log e x relative self fertility

relative self fertility =

sound seed set after self-pollination

sound seed set after cross -pollination

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide31

Embryonic lethals

post-zygotic

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide32

Prediction of empty seeds and proportion of selfed seeds (example for 10 embryonic lethals)

empty seeds

proportion of

selfed seeds

Selfed Pollen

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide33

Pollination and pollen movement

  • Wind-pollinated tropical species, e.g. Shorea robusta, Artocarpus heterophylla, Atelia herbert-smithii.
  • Wind-dispersed pollen are produced in surplus and distributed undirectionally.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide34

Pollination and pollen movement

Morphology of ovulate cone maximizes the probability of species- specific pollen capture through close-proximity interaction.

Unidirectional wind is deflected into cyclonic vortices.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide35

Pollination and pollen movement

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide36

Pollination and pollen movement

Fd = F0e-kd

ρ = 1.205 kg/m3, μ = 1.83 x 10 -5 kg/m s

Pollen Frequency

Distance

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide37

Stoke‘s law – Estimation of the sedimentation velocity of spherical bodies

r = radius of the pollen grain (m),

g = gravity (m/s2),

δ = density of pollen (kg/m3),

ρ = density of air (kg/m3),

μ = viscosity (absolute) of air (kg/m s).

ρ = 1.205 kg/m3, μ = 1.83 x 10 -5 kg/m s

European example: Larix decidua

experimental  0,130 m/s

predicted  0,127 m/s

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide38

Pollination and pollen movement

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide39

Pollination and pollen movement

Effective pollen distribution can be studied by

  • pollen trapping of single trees
  • pollen trapping of radioactive-labelled sources
  • paternity analysis.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide40

Animal-pollinations enhanced by

visual cues

Showy petals or sepals with obvious shape, size, and color.

Butterflies and birds are attracted to red and yellow colors.

Bees have vision that is shifted toward the blue end of our visible spectrum.

White or very pale color are importsant for nocturnal vectors.

olfactory cues

rewards for the visiting vector (pollen, nectar)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide41

Vector related questions:

Alternate host species to provide food ?

Example: Byrsonia crassifolia

Pattern of vector movement

e.g. „trap lining“ = day to day repeated vector movement over a relatively large area (larger bees, bat, butterfly, hummingbirds), typical for trees with relatively few flowers over extended periods  pronounced long distance gene flow, non random mating events

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide42

Mass flowering tree species 

Higher selfing rate, close-distance intertree movement

Example: Moca (Andira inermis): 70 bee species, only 8 were conspecific)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide43

Mating

Outcrossing rates may vary

  • from year to year
  • within the crown (in the apex higher rates)
  • with stand density.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide46

By now you should know

...........

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide51

Apomixis (=asexual embryogenesis)

Ability to reproduce asxually through seeds

  • seeds carry exclusively maternal genes

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide52

Pollination and pollen movement

species

pollen/cm2

Larix

Picea

Pinus

  • Wind-dispersed pollen are produced in surplus.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide53

Pollination and pollen movement

species

pollen/cm2

Larix 1300

Picea 18 000

Pinus 31 000

  • Wind-dispersed pollen are produced in surplus.

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide54

Pollination and pollen movement

Different pollination systems in conifers

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

slide55

Mating

Many tree species have a mixed-mating system.

Outcrossing rates obtained by means of

  • chlorophyll defect mutants
  • rare marker genes
  • gene markers (isozymes, DNA)

Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

ad