N-4-HEXANOYLSPERMIDINE, A NEW POLYAMINE-RELATED COMPOUND THAT ACCUMULATES DURING OVARY AND PETAL SENESCENCE IN PEA

A previously unknown polyamine conjugate that accumulates in senescing ovaries of pea (Pisum sativum L.) was shown by mass spectrometry, nuc lear magnetic resonance, and chemical synthesis to be N-4-hexanoylsper midine (hexanoyl-spd). This structure was indicated by analysis of the dansylated polyamine using fast atom bombardment mass spectrometry, f ollowing purification by highperformance liquid chromatography. Furthe rmore, acid hydrolysis of the compound yielded spermidine and hexanoic acid. H-1-nuclear magnetic resonance suggested that spermidine was su bstituted at N-4 in the conjugate. Hexanoyl-spd was synthesized, and i ts didansyl derivative was shown to have an identical mass spectrum an d high-performance liquid chromatography retention time as the derivat ized natural compound. Further confirmation of its structure was obtai ned by comparison of the synthetic and natural polyamines as trifluoro acetyl derivatives using gas chromatography-mass spectrometry. This ne w polyamine conjugate is present in pea ovaries at low levels at anthe sis and its concentration remains low in developing seeded fruit or in parthenocarpic fruit that have been induced by application of growth regulators to emasculated flowers or by topping the plant. Conjugate l evels are also low in parthenocarpic fruit induced naturally in the sl ender (la cry(S)) mutant. However, levels of hexanoyl-spd increase pro gressively in senescing petals and ovaries, beginning at anthesis or 2 d later, respectively.