Producción de etileno

ISSN 1021-4437, Russian Journal of Plant Physiology, 2007, Vol. 54, No. 1, pp. 80–88. © Pleiades Publishing, Ltd., 2007. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 1, pp. 92–101.

EXPERIMENTAL PAPERS

Effect of Suppression of Ethylene Biosynthesis on Flavor Products in Tomato Fruits1
H. Y. Gao*, B. Z. Zhu*, H. L. Zhu, Y. L. Zhang, Y. H. Xie, Y. C. Li, and Y. B. LuoCollege of Food Science and Nutritional Engineering, China Agricultural University, PO Box 204, Qinghua Donglu 17, Beijing, 100083 China; fax: (8610) 62-73-6479; e-mail: lyb@cau.edu.cn
Received January 16, 2006

Abstract—To elucidate the role of ethylene in the production of flavor compounds by tomato fruits, wild-type tomato (Lycopersicon esculentum L., cv. Lichun) and its transgenic antisenseLeACS2 line with suppressed ethylene biosynthesis were used. The metabolism of individual sugars was ethylene-independent. However, citric acid and malic acid were under ethylene regulation. The content of these acids was higher in transgenic tomato fruits and returned to normal level after transgenic fruits were treated with ethylene. Because most of amino acids, which are important precursors ofvolatiles, were shown to be correlated with ethylene, we surmise that amino acid-related aroma volatiles were also affected by ethylene. Headspace analysis of volatiles showed a significant accumulation of aldehydes in wild-type tomato fruits during fruit ripening and showed a dramatic decrease in most aroma volatiles in transgenic tomato fruits as compared with wild-type fruits. The production ofhexanal, hexanol, trans-2-heptenal, cis-3-hexanol, and carotenoid-related volatiles, except β-damascenone and β-ionone, was inhibited by suppression of ethylene biosynthesis. No remarkable differences were observed in the concentrations of cis-3-hexenal and trans-2-hexenal between transgenic and wild-type tomato fruits, indicating these two volatiles to be independent of ethylene. Thus, there arevarious regulation patterns of flavor profiles in tomato fruits by ethylene. DOI: 10.1134/S1021443707010128 Key words: Lycopersicon esculentum - tomato fruit - ethylene - volatiles - flavor

INTRODUCTION Ripe fruits demonstrate a wide range of diversity in pigmentation, texture, aroma, flavor, and nutrient composition. The biochemical and genetic regulation of fruit flavor production has recentlygained increased attention. Ethylene, an important phytohormone in climacteric fruits, initiates and accelerates fruit ripeningrelated processes, including changes in color, texture, and flavor. Thus, the relationship between ethylene and flavor is worthy of further study. During the past decade, many studies were focused on the characterization of genes encoding ethylene biosynthesis [1, 2], and theeffect of ethylene on the transcription and translation of many ripening-related genes [3, 4]. ACC (1-aminocyclopropane-1-carboxylic acid) synthase is the key enzyme responsible for ethylene biosynthesis. Inhibition of ethylene production by suppression of ACC synthesis can block normal fruit ripening, including degradation of chlorophylls, synthesis of carotenoids, solubilization of cell-wallpectins and variation in the levels
1 The

text was submitted by the authors in English. * Both authors equally contributed to this work. Abbreviations: ACC—1-aminocyclopropane-1-carboxylic acid; ACS—ACC synthase; DPA—days post anthesis; SPME—solidphase microextraction.

of volatiles and soluble sugars [5]. These findings suggest that ethylene may play an important role in the biosynthesis of thearoma volatiles in climacteric fruits. Tomato is a suitable model system for studying the role of ethylene in climacteric fruit ripening. As ripening progresses, tomato fruit color changes from green to red, fruit softening and textural changes occur, and the flavor increases. In this paper, tomato fruits were studied to elucidate the regulatory role of ethylene in fruit flavor development. Flavor...