Effect of cadmium on chlorophyll biosynthesis and enzymes of nitrogen assimilation in greening maize leaf segments: role of 2-oxoglutarate.
Supply of cadmium chloride (0.5 mM) inhibited chlorophyll formation in greening maize leaf segments, while lower concentration of Cd (0.01 mM) slightly enhanced it. Inclusion of 2-oxoglutarate (2-OG, 0.1-10 mM) in the incubation mixture increased chlorophyll content in the absence as well as presence of Cd. Substantial inhibition of chlorophyll formation by Cd was observed at longer treatment both in the absence and presence of 2-OG. When the tissue was pre-incubated with 2-OG or Cd, the inhibition (%) of chlorophyll formation by Cd was lowered in the presence of 2-OG. Treatment with Cd inhibited ALAD activity and ALA formation and the inhibition (%) of ALA formation by Cd was strongly reduced in the presence of 2-OG. Glutamate dehydrogenase (GDH) activity was increased by the supply of Cd both in the absence as well as presence of 2-OG. In the presence of 2-OG, Cd supply significantly increased glutamate synthase (GOGAT) activity and reduced inhibition (%) of glutamine synthetase (GS) activity. The results suggested the involvement of the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway of ammonia assimilation to provide the precursor, glutamate, for ALA synthesis under Cd toxicity and 2-OG supplementation.
Jain
Meeta
M
School of Biochemistry, Devi Ahilya Vishwavidyalaya, Takshashila Parisar, Khandwa Road, Indore 452 017, India.
Pal
Monika
M
Gupta
Priyanka
P
Gadre
Rekha
R
D000622:Aminolevulinic Acid / Q000037:antagonists & inhibitors / Q000378:metabolism; D019256:Cadmium Chloride / Q000494:pharmacology*; D002734:Chlorophyll / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D007656:Ketoglutaric Acids / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology; D000623:Porphobilinogen Synthase / Q000037:antagonists & inhibitors*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D003313:Zea mays / Q000187:drug effects* / Q000201:enzymology
D007656:Ketoglutaric Acids; D000644:Quaternary Ammonium Compounds; D002734:Chlorophyll; D000622:Aminolevulinic Acid; D000623:Porphobilinogen Synthase; D019256:Cadmium Chloride