AOX present in ETS of plants. When complex 4 of ETS is blocked, the formation of ATP and HEAT occurs due to AOX.

1. JAI NARAIN VYAS UNIVERSITY, JODHPUR
Alternative oxidase
BOT 302
Submitted to-
Dr. Bhana Ram Gadi
Submitted by-
Dinesh Mehra
M.Sc 3 rd sem.

2. ROTENO
NE
ANTIMYCIN A
CYANIDE
MALONATE
Salicyl hydroxamic acid
4
4
2

3. AOX can be specifically inhibited by salicylhydroxamic acid
(SHAM) and n‐propyl gallate.
If complex iv is inhibited -- 1 ATP & HEAT form.
 If complex I and complex iv both inhibited– only HEAT
form , no ATP synthesis.

4. The AOX exists in the inner mitochondrial membrane as a
homodimer in which two 32 kDa monomers interact non-
covalently to form a dimer.
When the 2 monomers are noncovalently linked it is in
reduced active form.
 when covalently linked, it is in its oxidised inactive form.

5. Activity of AOX is increased in following condition----
1.When ATP/ADP ratio is high.
2.In cold condition (heat generate)
3.Presence of α kito acids (pyruvate & glyoxylate) .
4.Drought, temp. generation of O2, H2O2.

8. Abiotic stress
• Aox has important roles to play in countering abiotic stress in
plants ranging from drought,light,& salinity to heavy metal
stress.
• High expression of AOX induces enhanced salt tolerance
capability in Medicago truncatula through regulation of ROS
and protection of photosystem.

9. Biotic stresss
• Plants responds to biotic stress by eliciting a salicylic acid mediated
hypersensitive reaction to limit pathogen spread and in the process
AOX expression is enhanced.
• Salicylic acid has been reported to inhibit mitochondrial ETC in
tobacco cell cultures and this inhibition might be inducing AOX
expression.
• AOX enhanced expressed causes lesions which causes programmed
cell death.

10. Gene expression of AOX
• Aox in higher plants is encoded by the nuclear genome.
• Aox was found to be encoded by a small family of nuclear genes
such as AOX1,AOX2
• The AOX 1 gene is widely known for its expression and it is
present in both mono and dicotyledon plant species.
• On theother hand AOX 2 gene is ususally expressed in
dicotyledon but absent in genome of all monocotyledon
species examined to date.

11. References..
Buchanan Biochemistry-Molecular-Biology-of-Plants
Alternative oxidase and plant stress tolerance ,Bedabrata
Sahaa, Gennadii Borovskiib, and Sanjib Kumar Pandaa
https://www.youtube.com/watch?v=NhcSPjTdHyM