Abstract
Phenylalanine ammonia-lyase (PAL) is the first key enzyme of the phenypropanoid pathway. A full-length cDNA of PAL gene was isolated from Juglans regia for the first time, and designated as JrPAL. The full-length cDNA of the JrPAL gene contained a 1935bp open reading frame encoding a 645-amino-acid protein with a calculated molecular weight of about 70.4 kD and isoelectric point (pI) of 6.7. The deduced JrPAL protein showed high identities with other plant PALs. Molecular modeling of JrPAL showed that the 3D model of JrPAL was similar to that of PAL protein from Petroselinum crispum (PcPAL), implying that JrPAL may have similar functions with PcPAL. Phylogenetic tree analysis revealed that JrPAL shared the same evolutionary ancestor of other PALs and had a closer relationship with other angiosperm species. Transcription analysis revealed that JrPAL was expressed in all tested tissues including roots, stems, and leaves, with the highest transcription level being found in roots. Expression profiling analyses by real-time PCR revealed that JrPAL expression was induced by a variety of abiotic and biotic stresses, including UV-B, wounding, cold, abscisic acid and salicylic acid.
Highlights
Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) catalyzes the deamination of phenylalanine to trans-cinnamic acid and ammonia, the first step in the biosynthesis of phenylpropanoids [1,2]
Using a RACE-PCR method, the full-length cDNA sequence of PAL gene was obtained from J. regia
Our results suggested that JrPAL shared a common evolutionary ancestor with other PALs based on conserved structure and sequence characteristics such as amino acid homologies and conserved motifs, and J. regia had a further relationship with those gymnosperm species
Summary
Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) catalyzes the deamination of phenylalanine to trans-cinnamic acid and ammonia, the first step in the biosynthesis of phenylpropanoids [1,2]. The PAL enzyme has been considered to be the one of the key enzymes in the biosynthesis of flavonoids [3,7], due to the central function of PAL as the first enzyme in phenylpropanoid derivative metabolism, and PAL is a key enzyme in plant stress response. Because of its crucial role in the biosynthesis of flavonoids, lignins, and phytoalexins and stress responses, PAL and its gene are widely studied [3,19]. J. regia is an agricultural commodity, but its leaves, barks, stems, pericarps, fruits, flowers and ligneous membranes are all applied for different medicinal use in China These fruits are attracting increasing interest as a healthy foodstuff because their regular consumption has been reported to decrease the risk of coronary heart disease [27,28,29]. The three-dimensional structural model, the phylogenetic trees, and expression profiles of JrPAL in different tissues and under stresses were investigated
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