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BIOSCI 340 > Fruit and ripening > Flashcards

Fruit and ripening Flashcards

1
Q

name some secondary metabolites of fruit

A

anthocyanins
chlorophyll
carotenoid

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2
Q

what gives fruit a taste/aroma?

A 
acid/sugar balance (breakage of storage to produce sugars)
aroma volatiles (majority are esters)
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3
Q

describe aspects of fruit from fertilisation until ripening (Dont eat me phase)

A 
growth and accumulation
unprotected seed development
nutrient accumulation
hard
higher acidity
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4
Q

describe aspects of fruit from ripening (Eat me phase)

A 
good to eat
protected seed development
metabolite changes
softening
reduction in acidity
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5
Q

name the different parts (anatomy) of an apple

A

stem, skin, cortex/flesh, seed, locules

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6
Q

describe some challenges for fruit breeders

A

generation times

because selected early, disease resistance can be lost

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7
Q

which micro RNA has been associated with fruit size?

A

mi172

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8
Q

what are some commercial problems for fruit growers?

A 
global competition
growth-related problems
knowing when to harvest
storage
shelf-life
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9
Q

how can biotechnology help fruit growers?

A

given premium fruit in novel varieties
directed breeding
post-harvest methodologies

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10
Q

True or false: continuous ethylene is required for ripening to proceed

A

True

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11
Q

describe the timeline of a GE approach to ripening

A

2-3 years generation time
can modify an elite cultivar
10-20years of paperwork

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12
Q

describe the timeline of a breeding approach to ripening

A

5 years per cross (10-20years)
large selection populations
need to have the natural mutation
release immediately

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13
Q

name some aspects of the plant cycle that ethylene controls

A 
seed germination
root initiation
root hair development
sex determination
fruit ripening
senescence
responses to biotic and abiotic stresses
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14
Q

describe systems I ethylene

A

auto-inhibitory

associated with wounding and disease resistance

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15
Q

describe systems II ethylene

A

auto-catalytic

associated with ripening

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16
Q

describe climacteric fruit ripening

A
  1. an autocatalytic increase in ethylene production
  2. an associated increase in respiration
  3. that 1 and 2 are accompanied by phenotypic changes that lead to ripening
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17
Q

what is the role of 1-MCP and ripening?

A

1-MCP delays ripening

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18
Q

describe ethylene synthesis

A

methionine –> S-AdoMet –> ACC –> ethylene

enzymes: SAM synthetase, ACC synthase, ACC oxidase

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19
Q

describe the role of ethylene

A
  1. ethylene turns of CTR1
  2. EIN2 gets cleaved
  3. EIN3 stabilised
  4. transcription activated
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20
Q

which ethylene receptors increase transcription?

A

ERS1 and ETR2

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21
Q

how do ethylene receptors affect ripening in tomato?

A

NR mutation in ERS1 stops ethylene-related ripening
suppression of NR –> normal ripening
suppression of ETR4 and ETR6 accelerates ripening (and overexpression slows it)

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22
Q

does ethylene have a role in ripening of climacteric fruits (eg apple)?

A

potentially, yes

23
Q

what effect does auxin have on ripening?

A

auxin suppresses ripening

high levels of GH3 (auxin conjugating enzymes) are associated with ripening

24
Q

what effect does ABA have on ripening?

A

suppression of ABA delays ripening

addition of ABA accelerates ripening

25
Q

what is fruit texture determined by?

A

anatomy and cellular structure
mechanical and physiological properties of cell wall
turgor pressure
membranes

26
Q

what causes juiciness in fruit?

A

cell wall swelling in melting textures causes internal juice to be released upon biting
loss of cell-cell adhesion in non-melting fruit causes loss of juice

27
Q

when do the biggest changes in fruit texture occur?

A

at ripening

28
Q

during ripening, what happens to the cell wall?

A

becomes more open and hydrophilic

  1. solubilisation of the pectin backbone
  2. deesterification
  3. depolymerisation
29
Q

how do biochemists induce solubilisation in the cell wall?

A

wash with more aggressive chemicals
CDTA (metal ion chelator)
insoluble fractions

30
Q

describe depolymerisation

A

the hydrolysis of polymers into shorter fragments
exo: cutting from the ends
endo: cutting in the middle
glycosyl hydrolase enzyme cleaves suagr bonds

31
Q

which enzyme causes the loss of galactan side chains on pectins?

A

B-galactosidase (BGal)

32
Q

which enzymes cause solubilisation of polyuronides?

A

expansins

33
Q

which enzymes cause deesterification of polyuronides?

A

pectin methyl esterase (PME)

34
Q

which enzymes cause depolymerisation of polyuronides?

A

polygalacturonase

35
Q

what was the first cell wall degrading enzyme characterised in tomato?

A

polygalacturonase

36
Q

does reduced softening occur with suppression of one degradation enzyme?

A

small effect, larger if more than one enzyme is suppressed

37
Q

what does suppression of endo-polygalacturonase 1 (PG1) lead to?

A

correlates with softening of fruit after storage

38
Q

what does overexpression of PG1 lead to?

A

crack of fruit skin (seen in apples)

39
Q

how many volatiles have been detected in tomatoes, and how many of those have an impact on human taste?

A

400 total

15-20 effect taste perception

40
Q

how does a genomic approach help in finding tomato volatiles?

A

identify genes regulated by ethylene and screen for aroma related genes

41
Q

how does a sequencing approach allow the identification of aroma genes?

A

uses homology

42
Q

what are some methods used to find the functional gene of interest?

A

large scale analysis of genes and their expression
microarrays
mRNA seq
qPCR

43
Q

how does mRNA sequencing work?

A

isolate RNA and convert to cDNA

sequence

44
Q

what are the main volatile compounds induced by ethylene?

A

esters

45
Q

how are esters synthesised?

A

alcohol + acid-CoA –> ester + H20

enzyme: acyl transferase (AT1)

46
Q

what is the RIN mutation in tomato?

A

reduced ethylene mutation

is a MADS TF

47
Q

where is auxin predominantly produced?

A

the seed

48
Q

what is the role of auxin

A

signals for seed to grow

delays ripening

49
Q

what is the apple SEP1/2 gene

A

acts like RIN

suppression of SEP1/2 stops ripening

50
Q

what is NOR TF

A

non ripening TF
suppression causes fruit not to ripen
more extreme than RIN

51
Q

what is CNR TF

A

SQUAMOSA binding protein TF

needed for RIN to work

52
Q

what is APA2a TF

A

AP2 like TF
increases expression at ripening
overexpression delays ripening
suppression increases ripening

53
Q

what is the role of cold on ripening?

A

cold binding factor 2 (CBF2) transactivates PG1

synergistic effect with ethylene

54
Q

what is PG1 regulated by?

A

EIN3 and CBF TFs

BIOSCI 340 (3 decks)

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