Characterization of Ethylene Biosynthesis Associated with Ripening in Banana Fruit

• Published in: Plant physiology (Bethesda) Vol. 121; no. 4; pp. 1257 - 1265
• Main Authors: Liu, X, Shiomi, S, Nakatsuka, A, Kubo, Y, Nakamura, R, Inaba, A
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Physiologists 01.12.1999
• Subjects: Amino Acid Oxidoreductases - genetics; Amino Acid Oxidoreductases - metabolism; ascorbate; Base Sequence; Biosynthesis; Climacteric; Cloning, Molecular; Complementary DNA; DNA Primers; Enzymes; Ethylene production; Ethylenes - biosynthesis; Ethylenes - pharmacology; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant - drug effects; Lyases - genetics; Lyases - metabolism; MA-ACO1 gene; MA-ACS1 gene; Messenger RNA; Molecular Genetics and Genomics; Musa; Oxidases; Plant Growth Regulators - biosynthesis; Plant Growth Regulators - pharmacology; Plants; Recombinant Proteins - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Ripening; Zingiberales - genetics; Zingiberales - physiology
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.121.4.1257

We investigated the characteristics of ethylene biosynthesis associated with ripening in banana (Musa sp. [AAA group, Cavendish subgroup] cv Grand Nain) fruit. MA-ACS1 encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase in banana fruit was the gene related to the ripening process and was inducible by exogenous ethylene. At the onset of the climacteric period in naturally ripened fruit, ethylene production increased greatly, with a sharp peak concomitant with an increase in the accumulation of MA-ACS1 mRNA, and then decreased rapidly. At the onset of ripening, the in vivo ACC oxidase activity was enhanced greatly, followed by an immediate and rapid decrease. Expression of the MA-ACO1 gene encoding banana ACC oxidase was detectable at the preclimacteric stage, increased when ripening commenced, and then remained high throughout the later ripening stage despite of a rapid reduction in the ACC oxidase activity. This discrepancy between enzyme activity and gene expression of ACC oxidase could be, at least in part, due to reduced contents of ascorbate and iron, cofactors for the enzyme, during ripening. Addition of these cofactors to the incubation medium greatly stimulated the in vivo ACC oxidase activity during late ripening stages. The results suggest that ethylene production in banana fruit is regulated by transcription of MA-ACS1 until climacteric rise and by reduction of ACC oxidase activity possibly through limited in situ availability of its cofactors once ripening has commenced, which in turn characterizes the sharp peak of ethylene production.