The ethanolic fermentation pathway supports respiration and lipid biosynthesis in tobacco pollen.
Rapid pollen tube growth requires a high rate of sugar metabolism to meet energetic and biosynthetic demands. Previous work on pollen sugar metabolism showed that tobacco pollen carry out efficient ethanolic fermentation concomitantly with a high rate of respiration (Bucher et al., 1995). Here we show that the products of fermentation, acetaldehyde and ethanol, are further metabolised in a pathway that bypasses mitochondrial PDH. The enzymes involved in this pathway are pyruvate decarboxylase, aldehyde dehydrogenase and acetyl-CoA synthetase. Radiolabelling experiments show that during tobacco pollen tube growth label of 14C-ethanol is incorporated into CO2 as well as into lipids and other higher molecular weight compounds. A role for the glyoxylate cycle appears unlikely since activity of malate synthase, a key enzyme of the glyoxylate cycle, could not be detected.
Mellema
Stefan
S
Institute of Plant Sciences, Altenbergrain 21, CH-3013 Bern, Switzerland.
Eichenberger
Waldemar
W
Rawyler
André
A
Suter
Marianne
M
Tadege
Million
M
Kuhlemeier
Cris
C
D000079:Acetaldehyde / Q000378:metabolism; D000106:Acetate-CoA Ligase / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002250:Carbon Radioisotopes; D004798:Enzymes / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005227:Fatty Acids / Q000096:biosynthesis*; D005285:Fermentation; D006038:Glyoxylates / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis; D008292:Malate Synthase / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D011058:Pollen / Q000254:growth & development / Q000378:metabolism*; D011767:Pyruvate Decarboxylase / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D014026:Nicotiana / Q000254:growth & development / Q000378:metabolism*
D002250:Carbon Radioisotopes; D004798:Enzymes; D005227:Fatty Acids; D006038:Glyoxylates; D008055:Lipids; D002245:Carbon Dioxide; D000431:Ethanol; D013395:Sucrose; D000444:Aldehyde Dehydrogenase; D008292:Malate Synthase; D011767:Pyruvate Decarboxylase; D000106:Acetate-CoA Ligase; D000079:Acetaldehyde; C031150:glyoxylic acid; D010100:Oxygen