This document discusses the role of alternative oxidase (AOX) in plant mitochondrial processes and stress responses. It highlights the effects of various inhibitors on ATP synthesis and the conditions that enhance AOX activity, including drought and abiotic stress. Additionally, it covers gene expression related to AOX and its importance in both abiotic and biotic stress tolerance in plants.

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