Differential expression of kenaf phenylalanine ammonia-lyase (PAL) ortholog during developmental stages and in response to abiotic stresses

Abstract

Phenylalanine ammonia-lyase (PAL) is a key enzyme in the phenylpropanoid pathway. A full-length of the gene putatively encoding phenylalanine ammonia-lyase (PAL) was cloned from kenaf (Hibiscus cannabinus L.) using degenerate primers and the RACE (rapid amplification of cDNA ends) method. The full-length PAL ortholog in kenaf consists of a 2,148 bp open reading frame encoding 715 amino acids (JQ779022). The deduced amino acid sequence showed high similarity to those of PAL from Ricinus communis (88%) and Vitis vinifera (86%). The expression of the PAL transcript was examined in different tissues, developmental stages, and after treatments with abiotic stresses (wound, NaCl, cold, H2O2, ABA, SA, MeJA and drought) using quantitative real-time reverse transcriptase polymerase chain reaction (QPCR). The PAL ortholog was differentially expressed in the different tissues and developmental stages. The highest transcript level of the PAL ortholog was observed in young (4-week-old) stem and mature flower tissues, with a certain level of expression in all tissues and organs tested. Three-week-old kenaf stem tissues were used to evaluate the effects of abiotic stresses on PAL ortholog expression. The highest transcript level of the PAL ortholog was observed at an early time point (1 or 6 h) after treatments with wound (1 h), H2O2 (6 h) and SA (6 h), while the highest transcript level was detected at the late time point (24 h) after treatments with NaCl, cold and ABA. The PAL ortholog was not significantly induced by MeJA, while drought repressed the PAL ortholog.