Reduction of benzenoid synthesis in petunia flowers reveals multiple pathways to benzoic acid and enhancement in auxin transport.
In plants, benzoic acid (BA) is believed to be synthesized from Phe through shortening of the propyl side chain by two carbons. It is hypothesized that this chain shortening occurs via either a beta-oxidative or non-beta-oxidative pathway. Previous in vivo isotope labeling and metabolic flux analysis of the benzenoid network in petunia (Petunia hybrida) flowers revealed that both pathways yield benzenoid compounds and that benzylbenzoate is an intermediate between L-Phe and BA. To test this hypothesis, we generated transgenic petunia plants in which the expression of BPBT, the gene encoding the enzyme that uses benzoyl-CoA and benzyl alcohol to make benzylbenzoate, was reduced or eliminated. Elimination of benzylbenzoate formation decreased the endogenous pool of BA and methylbenzoate emission but increased emission of benzyl alcohol and benzylaldehyde, confirming the contribution of benzylbenzoate to BA formation. Labeling experiments with 2H5-Phe revealed a dilution of isotopic abundance in most measured compounds in the dark, suggesting an alternative pathway from a precursor other than Phe, possibly phenylpyruvate. Suppression of BPBT activity also affected the overall morphology of petunia plants, resulting in larger flowers and leaves, thicker stems, and longer internodes, which was consistent with the increased auxin transport in transgenic plants. This suggests that BPBT is involved in metabolic processes in vegetative tissues as well.
Orlova
Irina
I
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907, USA.
Marshall-Colón
Amy
A
Schnepp
Jennifer
J
Wood
Barbara
B
Varbanova
Marina
M
Fridman
Eyal
E
Blakeslee
Joshua J
JJ
Peer
Wendy Ann
WA
Murphy
Angus S
AS
Rhodes
David
D
Pichersky
Eran
E
Dudareva
Natalia
N
D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D001554:Benzene / Q000737:chemistry / Q000378:metabolism*; D001565:Benzoates / Q000378:metabolism; D019817:Benzoic Acid / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport / Q000528:radiation effects; D003198:Computer Simulation; D003624:Darkness; D035264:Flowers / Q000201:enzymology / Q000378:metabolism* / Q000528:radiation effects; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000528:radiation effects; D032306:Petunia / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects; D018547:Plant Stems / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D036226:Seedlings / Q000201:enzymology / Q000528:radiation effects; D014835:Volatilization
D001565:Benzoates; D007210:Indoleacetic Acids; D010940:Plant Proteins; D019817:Benzoic Acid; D000217:Acyltransferases; D001554:Benzene