Plant Signalling 1 Flashcards

1
Q

Plant development

‘plastic’?

A

From a single-celled zygote:

  • cell division and differentiation
  • no cell migration, just expansion

Meristem cell retain character throughout life

‘Plastic’ development: largely determined by environmental factors promoting biochemical, physiological and developmental adaptation

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2
Q

Meristems

A

Plant stem cells that can differentiate into different types of cells. Main types are:

  • Shoot Apical Meristems (SAM)
  • Root Apical Meristem (RAM)
  • Auxillary meristems (repressed by SAM normally)
  • Lateral root meristems
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3
Q

Unable to flee danger, plants fight danger (herbivores)

A
  • Produce poisonous/unpleasant-tasting compounds
  • regrows parts that are eaten

Similar to animals, they perceive external stimuli and bring about cellular response via signalling pathways

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4
Q

Plant hormones

A

Act autonomously, transported to different parts of plant to bring various cellular responses.

  • Hormones and their signalling pathways interact (complex systems) to regulate growth/development
  • Small organic molecules and peptides that are locally produced and regulated with local and distant targets

Examples:

  • Auxins, cytokinins, ethylene, abscisic acid, Gibberellins
  • Also NO and Jasmonates
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5
Q

Jasmonates structure and roles

A

Fatty-acid derived signal molecules analogous to prostaglandins in animal cells
- derived from membrane lipids, pressed through Beta-oxidation

Role in plants:

  • Reproductive development
  • Stress response to UV, insects, microbes, temperature etc….
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6
Q

Role of Jasmonates in defence against insects (herbivores)

A

1) Insects wound plant by eating (insect-derived elicitors detected)
2) Jasmonic acid (JA) produced
3) JA triggers gene expression for local and systemic responses
- production of volatiles to attract parasitoids and prime defences of nearby plants
- up-regulate production of proteinase inhibitors to block insect digestive capabilities

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7
Q

Jasmonate Biosynthesis

A

Begins in chloroplast:
- cleavage of a-linolenic acid from chloroplast phospholipids (FA-derived)

Continues in peroxisome:

  • Beta-oxidation produces JA
  • The OPDA enters the peroxisome via the COMATOSE ABC transporter (active transport + ion trapping): proven through mutants accumulating less JA than wt

JA conjugation in the cytoplasm:
- conjugate to various molecules to form various derivates (aka oxylipins)

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8
Q

Understanding JA’s roles thanks to mutants

A

1) the opr3, fad3,7,8 triple mutant:
- males were sterile, susceptible to disease
- rescued by application of JA (proves mutation in JA production)

2) Coi1 mutants are insensitive to coronatine toxin used to screen for mutants:
- male sterile and insect attack can’t be rescued by JA application (mutation prevents response to JA)
- Coi1 normally encodes an F-box protein functioning within the ubiquitin pathway for protein degradation

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9
Q

Ubquitin conjugation pathway

A

E1 activates Ub, E2 transfers Ub to target protein, E3 provides specificity for Ub-protein binding and finally degraded by 26S proteosome

  • Coi1 = F-box protein component of multi-subunit SCF type E3 ligase
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10
Q

Jasmonate’s mechanism of activating gene expression

A

JAZ proteins = transcriptional repressors on JA response genes

  • JA-Ile (isoleucine) levels increase from stimulus activation (herbivory) promoting interaction between JAZ repressors and SCFcoi1
  • JAZ repressor is ubiquitinated and degraded allowing response gene to be expressed
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