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BIOSCI 340 > Fruit and ripening > Flashcards

Fruit and ripening Flashcards

(54 cards)

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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)?

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A

potentially, yes

23
Q

what effect does auxin have on ripening?

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A

auxin suppresses ripening

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

24
Q

what effect does ABA have on ripening?

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A

suppression of ABA delays ripening

addition of ABA accelerates ripening

25
what is fruit texture determined by?
anatomy and cellular structure mechanical and physiological properties of cell wall turgor pressure membranes
26
what causes juiciness in fruit?
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
when do the biggest changes in fruit texture occur?
at ripening
28
during ripening, what happens to the cell wall?
becomes more open and hydrophilic 1. solubilisation of the pectin backbone 2. deesterification 3. depolymerisation
29
how do biochemists induce solubilisation in the cell wall?
wash with more aggressive chemicals CDTA (metal ion chelator) insoluble fractions
30
describe depolymerisation
the hydrolysis of polymers into shorter fragments exo: cutting from the ends endo: cutting in the middle glycosyl hydrolase enzyme cleaves suagr bonds
31
which enzyme causes the loss of galactan side chains on pectins?
B-galactosidase (BGal)
32
which enzymes cause solubilisation of polyuronides?
expansins
33
which enzymes cause deesterification of polyuronides?
pectin methyl esterase (PME)
34
which enzymes cause depolymerisation of polyuronides?
polygalacturonase
35
what was the first cell wall degrading enzyme characterised in tomato?
polygalacturonase
36
does reduced softening occur with suppression of one degradation enzyme?
small effect, larger if more than one enzyme is suppressed
37
what does suppression of endo-polygalacturonase 1 (PG1) lead to?
correlates with softening of fruit after storage
38
what does overexpression of PG1 lead to?
crack of fruit skin (seen in apples)
39
how many volatiles have been detected in tomatoes, and how many of those have an impact on human taste?
400 total | 15-20 effect taste perception
40
how does a genomic approach help in finding tomato volatiles?
identify genes regulated by ethylene and screen for aroma related genes
41
how does a sequencing approach allow the identification of aroma genes?
uses homology
42
what are some methods used to find the functional gene of interest?
large scale analysis of genes and their expression microarrays mRNA seq qPCR
43
how does mRNA sequencing work?
isolate RNA and convert to cDNA | sequence
44
what are the main volatile compounds induced by ethylene?
esters
45
how are esters synthesised?
alcohol + acid-CoA --> ester + H20 | enzyme: acyl transferase (AT1)
46
what is the RIN mutation in tomato?
reduced ethylene mutation | is a MADS TF
47
where is auxin predominantly produced?
the seed
48
what is the role of auxin
signals for seed to grow | delays ripening
49
what is the apple SEP1/2 gene
acts like RIN | suppression of SEP1/2 stops ripening
50
what is NOR TF
non ripening TF suppression causes fruit not to ripen more extreme than RIN
51
what is CNR TF
SQUAMOSA binding protein TF | needed for RIN to work
52
what is APA2a TF
AP2 like TF increases expression at ripening overexpression delays ripening suppression increases ripening
53
what is the role of cold on ripening?
cold binding factor 2 (CBF2) transactivates PG1 | synergistic effect with ethylene
54
what is PG1 regulated by?
EIN3 and CBF TFs

BIOSCI 340 (3 decks)

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