Parent-offspring conflict is a concept in evolutionary biology that describes the tension arising between parents and their offspring over the allocation of resources. This conflict was first extensively discussed by Robert Trivers in 1974, building on the principles of evolutionary theory. The theory posits that while parents and their offspring share a substantial amount of genetic material, their genetic interests are not perfectly aligned, leading to conflicts of interest. Theoretical Basis The theory is based on the principle that both parents and offspring are driven by natural selection to maximize their own inclusive fitness. However, the ways they can maximize their fitness often conflict, especially over the distribution of resources such as food, care, and shelter. Parents' Perspective: From a parent's standpoint, the optimal strategy typically involves distributing resources equitably among all current and future offspring to maximize the total number of surviving offspring. This means that a parent may withhold some resources from a current offspring if it increases the survival and reproductive prospects of subsequent offspring. Offspring's Perspective: Each offspring, however, will benefit from obtaining more resources than the siblings to maximize its own survival and reproductive success. This can lead to a situation where the offspring demands more resources than the parent is willing to allocate. Manifestations of the Conflict 1. Weaning Conflict: This is one of the most common examples of parent-offspring conflict. Offspring may seek to prolong nursing to gain more nutrients, while the mother may attempt to wean them earlier to conserve resources for future offspring or her own survival. 2. Sibling Rivalry: Sibling rivalry can be seen as an extension of parent-offspring conflict where siblings compete for parental attention and resources. Here, the conflict manifests not directly between parent and offspring but mediated through competition among siblings. 3. Reproductive Conflict: In some species, especially birds, offspring may attempt to manipulate parents into providing more care by feigning hunger or weakness. Parents need to discern genuine signals of need from manipulative ones to distribute care optimally among all offspring. Evolutionary Consequences Resource Allocation Strategies: Evolution shapes both parental and offspring strategies for resource allocation. Parents evolve mechanisms to detect and counteract manipulation by offspring, while offspring evolve more sophisticated strategies to extract resources. Impact on Life History Traits: Parent-offspring conflict can influence key life history traits such as growth rates, age at independence, and reproductive strategy. For example, faster growth can be an adaptive strategy for offspring in response to parental underinvestment.

1. Welcome
Brahmesh Reddy B R
PAMB 2088
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

2. K A Ravishankar, R Uma Shaanker, K N Ganeshaiah
War of hormones over resource allocation to
seeds:
Strategies and counter-strategies of offspring and maternal parent
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

3. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

4. Nutshell
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Offspring - demands additional resources
Mother - equally distributes resources
‘Conflict of interest’

5. Nutshell
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Offspring - demands additional resources
BUT HOW?
Something in the seed that must attract the resources - MAGNET?

6. Nutshell
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Mother - equally distributes resources
HOW TO MANAGE GREEDY OFFSPRINGS?
Something in the MOTHER that must INHIBIT the flow of resources -
Another MAGNET?

7. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother offspring
resources

8. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother offspring
resources
Begging
magnets
Inhibiting
magnets

9. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring
resources
Will the mother be willing to produce these
begging magnets and supply to the offspring?

10. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring
resources
Will the mother be willing to produce these
begging magnets and supply to the offspring?
IT'S A BIG NO

11. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring
resources
So, if the mother is not supplying
What's the next best alternative?

12. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring
resources
So, if the mother is not supplying
What's the next best alternative?
SELF SYNTHESIS?

13. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring
resources
If the offspring is preparing for war,
Mother also prepares itself

14. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring
resources
If the offspring is preparing for war,
Mother also prepares itself
MOTHER ALSO SYNTHESIZES INHIBITING MAGNETS

15. “The development of seeds is characterized by the
production of two distinct kinds of hormones that are
synthesized in two disparate tissues and have opposite
functions in mobilizing resources”
What authors say…
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

16. Inhibiting magnets - ABA
Begging magnets - Ax, Ck & GA
Two distinct hormones
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

17. Inhibiting magnets - ABA
Begging magnets - Ax, Ck & GA
Two distinct hormones…
synthesised in disparate tissues…
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring

18. Inhibiting magnets - ABA
Begging magnets - Ax, Ck & GA
Two distinct hormones…
synthesised in disparate tissues…
With opposite function
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
mother
offspring

19. Mother - passive participant of resource mobilization
∵ phloem vessels emanating from the maternal tissue never grow into the developing
seed
Offspring - active participant of resource mobilization
∴ the extent to which the resources flow into the offspring depends completely on its
ability to actively draw them across the passive barriers of mother tissue
Architecture between mother and seeds
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

20. 1. Increasing differentiation of sieve tubes connecting sinks to
source
2. Enhanced metabolic and enzyme rates in sinks
3. Increasing size and rate of cell division in sink tissue
How do seeds achieve this drawing ability?
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

21. 1. Increasing differentiation of sieve tubes connecting sinks to
source
2. Enhanced metabolic and enzyme rates in sinks
3. Increasing size and rate of cell division in sink tissue
How do seeds achieve this drawing ability?
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Laying pipelines for
flow of resources
{

22. 1. Increasing differentiation of sieve tubes connecting sinks to
source
2. Enhanced metabolic and enzyme rates in sinks
3. Increasing size and rate of cell division in sink tissue
How do seeds achieve this drawing ability?
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Resource demanding
hungry activities
{

23. Pea / GA mutant seeds
● Abortion rate: mutants > Wild type (50% )
● If matured, low seed weight
∴ increased GA in WT seeds facilitate mobilization of resources
Some evidences
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

24. Barley / isogenic lines
● High Ck: increased mitosis rate in endosperm tissue
● Increased seed weight when compared with seeds with low Ck
Some evidences
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

25. Is it true that begging hormones
are synthesized in seed?
Pea / mutant mother
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
ga/ga’
Mutant mother
GA/ga’
Fo
GA/GA
Wild pollen
These Fo seeds had gibberellic acid
levels and seed weights comparable
to those of the wild parent and
significantly more than the selfed
seeds of the mutant mother

26. GA content:
GA/GA ⪞ GA/ga’ ≫ ga’/ga’
though the mutant mother was
deficient in GA, the presence of a
single copy of the wild type allele in
the hybrid embryo could restore the
normal seed development
Is it true that begging hormones
are synthesized in seed?
Pea / mutant mother
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
ga/ga’
Mutant mother
GA/ga’
Fo
GA/GA
Wild pollen

27. What's directing seed to produce begging hormones?
● Now we know, maternal genetic system does not support begging
hormone rather supports inhibiting hormone
● If the maternal genetics system is not supporting and still the
begging hormone is produced…where is it coming from?
● Is pollen genetic system carrying the begging gene?
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

28. ● post–fertilization increase of hormones in the ovule is known to be
facilitated by the enzymatic machinery contributed by the pollen
tube that fertilizes them
● Pollen grains of a variety of species are very rich sources of such
hormones and are frequently shown to supplement the hormone
pool of the ovules they fertilize
Begging gene from the pollen
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

29. ● orchid pollen are known to be a rich source of indole acetic acid
● Atleast two different fractions of gibberellic acid are found in pine
pollen grains
● Studies have shown that in these and in other species, ovules
receive such hormones from the pollen grains at the time of
fertilization
Begging gene from the pollen
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

30. Two ways
1. mother invests certain optimal amount of resources into the
offspring independent of the offspring's ability to draw resources
2. mother offers resources to offspring in proportion to that
demanded by the latter.
Different ways of food supply by mother
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

31. mother invests certain optimal amount of resources into the offspring
independent of the offspring's ability to draw resources
1st pathway of supply
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Mother
(10)
Offspring 1
(3)
Offspring 2
(3)
5 5

32. mother offers resources to offspring in proportion to that demanded by
the latter
2nd pathway of supply
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Mother
(10)
Offspring 1
(5)
Offspring 2
(15)
2.5 7.5

33. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Different ways of food supply by mother
HORMONES - who’s and where?
Two ways:
1. If mother adopts the first strategy then the source of the resource
mobilizing hormone could well be the maternal tissue per se
2. if it adopts the second strategy, then the source of resource
mobilizing hormone would be clearly the offspring

34. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Different ways of food supply by mother
HORMONES - who’s and where?
Two ways:
1. If mother adopts the first strategy then the source of the resource
mobilizing hormone could well be the maternal tissue per se
2. if it adopts the second strategy, then the source of resource
mobilizing hormone would be clearly the offspring
Since the current understandings the predictions fit well with POC, it was
proposed that the synthesis of resource mobilizing hormone in the offspring might
likely represent sibling rivalry than mere strategies of the offspring to survive

35. Maternal strategy
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

36. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Maternal strategy
selection can be expected to favour the maternal tissue to
produce, during these early phases of seed development,
hormones that antagonize or quench the resource demand
by the offspring

37. Maternal strategy -
Implications Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
1. the hormones that inhibit the resource
mobilization into the seed are produced at the
stage corresponding to that of the synthesis of
resource mobilizing hormone by the offspring
2. they are synthesized exclusively by the maternal
tissue

38. abscisic acid (ABA) seems to be the most probable
candidate that might aid the maternal tissue in
subduing the offspring–driven resource mobilization
to developing ovules
ABA inhibits the mobilization of assimilates in several
systems and is antagonistic to the effects of growth
promoters (Ax, GA, Ck)
ABA - inhibiting hormone
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

39. ABA - inhibiting hormone
Example:
enriching winter wheat plants with ABA greatly
reduced the translocation of 14C–sucrose into the
developing ears resulting in reduced grain dry weight
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

40. ABA - inhibiting hormone
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Example:
In barley, application of ABA to developing grains
during the first week of anthesis significantly reduced
the movement of assimilates to the grains as
compared to the control grains

41. ABA - inhibiting hormone
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Example:
ABA application reduced the gibberellic acid induced
sucrose uptake in excised veins of Pisum sativum
ABA has also been shown to inhibit cell division in
endosperm tissue.

42. Temporal pattern
of ABA production
why?
If the seeds /
offsprings are
accumulating begging
hormones then the
mother plant should
also be ready to
produce the inhibiting
hormone in order to
counteract
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

43. Temporal pattern
of ABA production
Two peaks
the first during the
early stages of
resource accumulation
in the seed
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

44. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
ABA production during
early stages of resource accumulation

45. Temporal pattern
of ABA production
Two peaks
the first during the
early stages of
resource accumulation
in the seed and
the second during the
seed maturation
period
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

46. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
resource accumulation
Seed maturation

47. Temporal pattern
of ABA production
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
2nd peak
Functional significance
● LEA synthesis -
protect the embryos
against desiccation
damage
● the inhibition of
precocious
germination of seeds
on the mother plant

48. 1st peak
Functional significance
?
Temporal pattern
of ABA production
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
studies suggest that the
early peak of ABA
accumulation coincides
substantially with the
peak synthesis of
resource mobilizing
hormones in developing
seeds

49. Resource mobilization hormones
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

50. Temporal peaks of all
hormones in seeds
Let us try to overlap all peaks of all the
hormones produced in seeds and ones produced
by mother and translocated into the seeds
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

51. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

52. Such temporal correspondence of ABA accumulation with that of resource
mobilizing hormones can be expected to subdue the sink strength of developing
seeds.
In other words, the pattern of accumulation of ABA during early stages of seed
development represents a maternal counter–strategy of quenching the greedy
demand of the selfish offspring. Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

53. Is there a proof
that ABA is
produced by the
mother
YES!!!
Arabidopsis
● WT - Aba / Aba
● Mutant - aba / aba
WT exhibit an early peak of ABA
accumulation 10 days after
fertilization coinciding with the
seed-filling period while that of
ABA deficient mutants do not
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

54. Is there a proof
that ABA is
produced by the
mother
YES!!!
Two types of mothers
Fo - Aba /aba
Fo growing on WT (Aba/Aba)
mother show peak while
Fo growing on mutant (aba/aba)
mother did not exhibit this peak
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

55. Clearly, embryos by themselves
do not seem to produce ABA
though they are genetically
capable (Aba allele).
Rather ABA of the first peak
appears to be synthesized only in
the maternal tissue but is then
translocated to the embryo
Hence proved
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

56. Another possibility is that the
ABA is produced in the
endosperm by the selective
expression of maternal allele with
the corresponding allele from the
paternal parent being imprinted.
Hence proved
Another possibility
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah

57. ABA, the hormone that inhibits resource–mobilization into
offspring tissue, appears to be synthesized exclusively in the
maternal tissue and translocated to the embryo.
This supports prediction that maternal tissues are selected to
produce hormones that quench the offspring driven resource
drawing ability
conclusion