The relationship of the genes of PAL (phenylalanine ammonia-lyase) and scopoletin was explored to reveal the key gene involved in PAL activity, PAL expression and scopoletin accumulation in noni (Morinda citrifolia L.) leaves and fruit. Our results display how the enzyme activity of PAL in noni fruit and leaves increases gradually with the leaves maturity, and exogenous ethephon induces PAL activity in noni leaves, which is consistent with the scopoletin accumulation law. Based on our previous transcriptome data, three PAL fragments were retrieved, and their full lengths were cloned via RACE; named as McPAL1, McPAL2 and McPAL3. The analysis of qRT-PCR showed that McPAL3 is expressed in the leaves and mature fruit, McPAL2 in the leaves only and McPAL1 mainly in the young stage of fruit. Ethephon induced the expression of McPAL2 and McPAL3 in the leaves, and McPAL1 and McPAL3 in the fruit. In noni fruit treated with ethephon, the expression pattern of McPAL3 was consistent with the trend of the scopoletin content and total PAL activity. We conclude that McPAL3 is the key gene involved in the accumulation of scopoletin, which can be induced by ethylene (ETH).

探讨PAL（苯丙氨酸解氨酶）基因与东莨菪碱的关系，揭示诺丽( Morinda citrifolia L.)叶片和果实中PAL活性、PAL表达及东莨菪素积累的关键基因。我们的研究结果表明诺丽果和叶子中PAL的酶活性如何随着叶子的成熟而逐渐增加，外源乙烯利在诺丽叶中诱导PAL活性，这符合东莨菪碱的积累规律。根据我们之前的转录组数据，检索到了三个PAL片段，并通过 RACE 克隆了它们的全长；命名为McPAL1、McPAL2和McPAL3。qRT-PCR 分析表明McPAL3McPAL2仅在叶片和成熟果实中表达，McPAL1主要在果实幼龄期表达。乙烯利诱导表达McPAL2和McPAL3在叶子和McPAL1和McPAL3的水果。在用乙烯利处理的诺丽果中，McPAL3的表达模式与东莨菪素含量和总PAL活性的趋势一致。我们得出结论，McPAL3是参与东莨菪碱积累的关键基因，可由乙烯 (ETH) 诱导。