Tol to abiotic - L7 Flashcards
Give examples of primary stresses
(drought, salinity, cold, heat, chemical pollution)
understand and then exploit nature by looking at what type of plants?
cacti )drought tol0 halophytes (salt tol( al tol plants
Functions of Stress Inducible Genes in Stress Tolerance Response - proteins are categorised into what two groups why?
Functional proteins – thought to function in stress tolerance
Regulatory proteins – regulation of signal transduction thought to be involved in the stress response
Primary stresses trigger what
are often interconnected and cause cellular damage and secondary stresses e.g. osmotic & oxidative stress
The initial stress signals trigger the downstream signaling process & transcription controls
These activate stress-responsive mechanisms to re-establish homeostasis & protect & repair damaged proteins and membranes
what are the four functional groups stress tolerance related molecules are in?
(1) detoxification
(2) chaperoning
(3) late embryogenesis abundant (LEA) protein functions
(4) osmoprotection
what are detoxification molecules, discuss examples
High temperatures or water deficit lead to the production of toxic reactive oxygen combinations, causing extensive cellular damage and inhibition of photosynthesis (oxidative stress).
ascorbate peroxidase (APX)
superoxide dismutase (SOD)
SOD is the first enzyme in the enzymatic antioxidative pathway and halophytic plants, such as mangroves, have been reported to have a high level of SOD activity
rice w/ SOD more drought tol :)
What are chaperoning proteins?
Some specific stress-associated proteins:
- responsible for:
protein renaturisation, memebrane stabalisation, folding
Heat (Cold) Shock Proteins (HSPs), have been shown to have particularly important stress-related chaperone functions in plants
help in protein folding prevent both newly synthesised polypeptide chains and assembled subunits from aggregating into nonfunctional structures.
WHat are LEAs?
Late Embryogenesis Abundant (LEA) Protein Function
LEA proteins are produced in response to dehydration stress and function in water status stabilisation
LEA and LEA-type genes are found universally in plants. They accumulate in seeds during the late stages of embryogenesis and are associated with the acquisition of desiccation tolerance under drought, heat, cold, salt, and ABA stress
e.g. Dehydrins
DHN-5 (Wheat) was ectopically overexpressed in Arabidopsis
What are osmoprotectants? What are the 3 main groups?
Osmoprotection involves the up-regulation of compatible solutes (osmolytes) that function primarily to maintain cell turgor
The three major groups of compatible solutes are:
- amino acids (such as proline) - quaternary amines (glycine betaine (GlyBet), polyamines) - polyol/sugars (such as mannitol, galactinol, and trehalose)
Drought specific genes can be grouped into three major categories:
(1) Genes involved in signal transduction pathways and transcriptional control
(2) Genes with membrane and protein protection functions
(3) Genes assisting with water and ion uptake and transport
Drought/Salt tolerance
Examples involving manipulation of complex responses (signalling, transcription):
IPT H+-Ppase ABA TFs DN-5
What does IPT do?
isopentyl transferase - drought tol!
biosynthesis of cytokinin (senescence inhibitor).
It is under control of a senescence associated receptor protein kinase promoter (PSARK). SARK promoter
The inducible characteristicsofSARKallowed the production of CKs in all tissues facingdrought-induced stress, which in turn enabled plants to mounta vigorous acclimation response resulting in enhanced droughttolerance with minimal yield loss
Who engineered IPT ? when ?
Rivero 2007 PNAS
Tobacco engineered with inducible SARK promoter and IPT (isopentyl transferase gene) also used herbicide res gene + 35S const prom.
by agrobacterium mediated transfer
signific more drought tol than WT as cytokinin production inhibits senescence in leaves
What gene is used to help with drought/salt stress via upregulation of solutes
H+-pyrosphosphotase gene: AVP1
what gene increases ABA to help salt/drought
AtZEP (zeaxanthin epoxidase) - zeaxanthin ABA precursor
