Disease relevance of PAL1

• Promoters of the Cauliflower Mosaic Virus 35S gene, the bacterial nopaline synthase, rooting loci (rol) and T-cyt genes and the plant-derived phenylalanine ammonia-lyase I gene, which are highly active in non-infected roots, were all downregulated in the feeding structures as indicated by the strong decrease of GUS activity inside these structures [1].
• Tyrosine ammonia lyase was substituted for phenylalanine ammonia lyase and cinnamate-4-hydroxylase in our E. coli clones and three different growth media were tested [2].
• Tobacco plants over-expressing L-phenylalanine ammonia-lyase (PAL(+)) produce high levels of chlorogenic acid (CGA) and exhibit markedly reduced susceptibility to infection with the fungal pathogen Cercospora nicotianae, although their resistance to tobacco mosaic virus (TMV) is unchanged [3].

High impact information on PAL1

• Together, from the molecular phenotype, common and specific functions of PAL1 and PAL2 are delineated, and PAL1 is qualified as being more important for the generation of phenylpropanoids [4].
• FB1 susceptibility of wild-type protoplasts decreases in the dark, as does the cellular content of phenylalanine ammonia-lyase, a light-inducible enzyme involved in SA biosynthesis [5].
• We investigated the signal transduction processes involved in the induction of chalcone synthase (CHS) and phenylalanine ammonia-lyase (PAL) gene expression by UV-B and UV-A/blue light in an Arabidopsis cell suspension culture [6].
• The regulation of the PAL1 gene was examined by analysis of beta-glucuronidase (GUS) activity in transgenic Arabidopsis containing PAL1-GUS gene fusions [7].
• In addition, NtMEK2-SIPK/WIPK cascade appears to control the expression of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) and l-phenylalanine ammonia lyase (PAL), two defense genes encoding key enzymes in the phytoalexin and salicylic acid biosynthesis pathways [8].

Biological context of PAL1

• Previously identified promoter motifs plus several additional sequence motifs were found in the promoter regions of PAL1 and PAL2 [9].
• Molecular phenotyping of the pal1 and pal2 mutants of Arabidopsis thaliana reveals far-reaching consequences on phenylpropanoid, amino acid, and carbohydrate metabolism [4].
• In this study, recombinant native AtPAL1, 2, and 4 were demonstrated to be catalytically competent for l-phenylalanine deamination, whereas AtPAL3, obtained as a N-terminal His-tagged protein, was of very low activity and only detectable at high substrate concentrations [10].
• Furthermore, plants expressing a nahG transgene or treated with a phenylalanine ammonia lyase (PAL) inhibitor showed enhanced symptoms, suggesting that SA synthesized via PAL, and not via isochorismate synthase (ICS), mediates lesion development [11].
• Phenylalanine ammonia-lyase (PAL) is a key enzyme in pathogen defence, stress response and secondary metabolism and is subject to post-translational phosphorylation [12].

Associations of PAL1 with chemical compounds

• However, the observed phenotypes were correlated with the amount of total shoot anthocyanin at low temperature and with the transcription of the flavonoid pathway genes PAL1 and CHS [13].
• As anticipated, PAL activities with l-tyrosine were either low (AtPAL1, 2, and 4) or undetectable (AtPAL3), thereby establishing that l-Phe is the true physiological substrate [10].
• Several characteristic defence reactions, including activation of phenylalanine ammonia-lyase, accumulation of salicylic acid (SA), expression of the pathogenesis-related protein PR-1 and the development of a microscopically defined hypersensitive response, proved to be light dependent [14].

Other interactions of PAL1

• Expression of PAL1 and PAL2 is both qualitatively and quantitatively similar in different plant organs and under various inductive conditions [9].
• C4H (CYP73A5) expression was apparently coordinated in Arabidopsis with both PAL1 and 4CL in response to light and wounding [15].
• Suppressed phenylalanine ammonia-lyase activity after heat shock in transgenic Nicotiana plumbaginifolia containing an Arabidopsis HSP18.2-parsley PAL2 chimera gene [16].
• Molecular identification of phenylalanine ammonia-lyase as a substrate of a specific constitutively active Arabidopsis CDPK expressed in maize protoplasts [12].

References