This Presentation helps the Studetns preparing for the CSIR-NET in Life Sciences. Not only CSIR but also the exams like DBT, GATE, ICMR, TIFR and all the other exams related to Life Sciences.
For MSc entrance exams too.
This topic deals with the Plant Metabolic process. It is under the subject Plant Physiology.
2. Vernalisation(Exposure to low temperature)
Exposure of Plants to low temperatures to induce flowering is called
“Vernalisation”.
Winter annuals and Winter biannual show vernalisation.
Vernalisation temperatures range from 1-10 ֯C.
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3. “SAM” is the perception site of Vernalisation.
In some cases, seeds can also be vernalized.
After Vernalisation, if the plant is exposed to warm temperatures, then
flowering is inhibited=Devernalisation.
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5. VERNALIN-III is the hormone of vernalisation and is equivalent to
FT-protein of Photoperiodism.
Vernalisation involves regulation of FLC(FLOWERING LOCUS C)
gene.
Active FLC inhibits Vernalisation and Flowering.
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6. FLC gene expression is activated by proteins like “FRIGADA”.
FLC gene expression is promoted by Chromatin remodeling or
Epigenetic modifications, such as Histone Acetylation.
This leads to “Decondensation of FLC gene chromatin” and FLC
gene expression which inhibits Vernalisation/Flowering.
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7. Vernalisation pathway involves FLC gene repression by Epigenetic
modifications such as Histone Deacetylation and H3K9Me and
H3K27Me3.
This causes condensation of gene Chromatin and FLC gene
repression.
FLC gene expression is also prevented b antisense gene silencing
involving cool air/cold air Antis-sense transcripts.
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10. In Animal cells, application of Cyanide inhibits cytochrome Oxidase
or Complex-IV and also inhibits Electron transport to Oxygen.
In Plant cells, application of Cyanide inhibits cytochrome Oxidase
complex but electron transport to Oxygen is not inhibited.
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11. This is because, an Alternative Oxidase(AOX) continues to transfer
electrons to oxygen.
This mechanism is called “Cyanide resistant respiratory pathway or
AOX pathway”.
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12. However, AOX pathway is inhibited by SHAM=Salicyl Hydroxamic
Acid and n-Propyl Gallate.
Hence, SHAM sensitive oxygen uptake refers to “AOX pathway”.
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13. AOX pathway is activated by complex-III inhibits or complex-IV
inhibitors.
In AOX pathway, complex-III and complex-IV are by-passed.
Due to this, the H+ -gradient across inner Mitochondrial membrane is
less in AOX-pathway.
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14. Consequently, in AOX-pathway less no.of ATPs are produced and
more heat energy is released.
NADH= 4 H+ and
Therefore, 1 NADH=1 ATP
1 FADH2 = 0 H+ (nil)
Therefore, 1 FADH2= 0 ATP (nil)
Therefore, P/O ratio of NADH=1:1
P/O ratio of FADH2 =0:1
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15. AOX is a homodimer and the two monomers are connected by a –S-
S- bond.
AOX contains di-iron centre.
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16. Regulation of AOX pathway:-
Carbon status of the cell or carbon metabolites such as ketoacids
pyruvate and Glyoxylate activate AOX pathway
Reduction of –S-S- bonds between the two monomers also activates
AOX.
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18. Over-reduction of Cytochrome pathway (Complex-III & complex-
IV).
Cytosolic ADP ATP levels are low.
Complex-III & Complex-IV inhibitors.
Stress factors such as chilling stress and freezing stress.
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19. Xenobiotics such as Herbicides regulates AOX pathway.
Mitochondrial protein synthesis inhibitory also regulates AOX
pathway.
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