Molecular cloning and expression of four phenylalanine ammonia lyase genes from banana interacting with Fusarium oxysporum

Phenylalanine ammonia lyase (PAL) is the first enzyme in the phenylpropanoid pathway. In this study, we describe the molecular characteristics of four PAL genes (MaPAL1, MaPAL2, MaPAL3, and MaPAL4) cloned from banana (Musa acuminata L. AAA group, cv. Cavendish) using a rapid amplification of cDNA ends and real time quantitative PCR. The predicted molecular masses of corresponding PALs ranged from 70.2 to 77.3 kDa and their isoelectric points were acidic. At the amino acid level, they shared a high sequence similarity with PALs in the banana DH-Pahang (AA group) genome. Phylogenetic analysis shows that the deduced amino acid sequences of MaPALs had also a high similarity with PALs of other plant species. Expression analysis by semi-quantitative reverse transcriptase PCR reveals that these genes were differentially expressed in various tissues. Enzyme activity of PAL and expression of MaPALs in bananas were induced after infection with Fusarium oxysporum f. sp cubense Tropical Race 4. Our findings suggest that MaPALs play important roles in banana resistance to F. oxysporum.