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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #165414
Title: MOLECULAR PHENOTYPING OF THE ARABIDOPSIS PAL1 AND PAL2 MUTANTS REVEALS FAR-REACHING CONSEQUENCES ON PHENYLPROPANOID, AMINO ACID AND CARBOHYDRATE METABOLISM

Author
item RHODE, ANTJE - VIB, GENT, BELGIUM
item MORREEL, KRIS - VIB, GENT, BELGIUM
item Ralph, John
item VAN DOORSSELAERE, J - VIB, GENT, BELGIUM
item GOEMINNE, G - VIB, GENT, BELGIUM
item JOSSELEAU, JEAN-PAUL - CERMAV, FRANCE
item VUYLSTEKE, MAMIK - VIB, GENT, BELGIUM
item VAN BEEUMEN, JOSS - VIB, GENT, BELGIUM
item MESSENS, ERIC - VIB, GENT, BELGIUM
item BOERJAN, WOUT - VIB, GENT, BELGIUM

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2004
Publication Date: 10/4/2004
Citation: Rhode, A., Morreel, K., Ralph, J., Van Doorsselaere, J., Goeminne, G., Josseleau, J., Vuylsteke, M., Van Beeumen, J., Messens, E., Boerjan, W. 2004. Molecular phenotyping of the arabidopsis pal1 and pal2 mutants reveals far-reaching consequences on phenylpropanoid, amino acid and carbohydrate metabolism. The Plant Cell. 16:2749-2771.

Interpretive Summary: Lignin is a polymer that is present in plant cell walls, where it provides strength and impermeability, allowing transport of water and nutrients. There is wide interest in understanding the process of lignin biosynthesis and deposition because of its economic relevance: during chemical pulping, lignin needs to be extracted from the cellulose, a process that is expensive and environmentally hazardous. In addition, lignin limits the digestibility of forages. Hence, plant varieties with altered lignin contents or altered lignin structure may have improved performance as fodder crops or in the production of paper and pulp. Here collaborators in Belgium have intensely studied the genes for the very first enzyme, PAL, in the lignin pathway. In the absence of clearly visible plant changes in mutants, significant modifications can be observed by genetic and biochemical analysis. The disruption of PAL is found to produce far-reaching consequences on the transcription of genes encoding enzymes involved in the biosynthesis of lignin and other phenolic compounds, as well as carbohydrate and amino acid metabolism. Researchers at the Diary Forage Research Center were involved in the discovery of compounds in the mutants that have not been previously reported, allowing common and specific functions of two PAL genes to be delineated, and identifying which gene is involved in lignin biosynthesis. Such studies are ultimately aimed at improving the utilization of valuable plant resources.

Technical Abstract: Phenylalanine ammonia-lyase, the first enzyme of the phenylpropanoid pathway, has been extensively studied in various plants. Whereas its enzymatic function is well established, a complete appreciation of the functions of different PAL isoforms has been hampered by the lack of tools to reveal the full spectrum of metabolic and transcriptomic consequences of a mutation. Here, we show that in the absence of clear phenotypic alterations in the Arabidopsis pal1 and pal2 single mutants and with limited phenotypic alterations in the pal1 pal2 double mutant, significant modifications occur in the transcriptome and metabolome of the pal mutants. Genome-wide transcriptome profiling revealed far-reaching consequences of the disruption of PAL function on the transcription of genes encoding enzymes of the phenylpropanoid biosynthesis, carbohydrate metabolism, and amino acid metabolism establishing a clear link between primary and secondary metabolism. Corresponding biochemical changes include a decrease in the three major flavonol glycosides, glycosylated vanillic acid, scopolin and two novel feruloyl malates coupled to coniferyl alcohol in the double mutant. Lignin analysis shows a significant reduction in lignin content and an increase in the S/G ratio of lignin monomers. Together, from the molecular phenotype, common and specific functions of PAL1 and PAL2 are delineated. Whereas both enzymes contribute to the production of lignin precursors, PAL1 is of higher importance for the generation of flavonoids in the inflorescence stem.