Developmental Change in C₆-Aldehyde Formation by Soybean Leaves

Abstract

Damage to plant leaves by wounding or freezing induces the production of large amounts of C6-compounds. However, the control of formation of these compounds in leaves is not yet clear. In the current study, C6-aldehyde formation by freeze-injured soybean leaves of different ages (based on the leaf positions on the plant) at stage Rl of plant development was investigated. The results demonstrate that C6-aldehyde formation by the soybean (Glycine max L.) leaves changes as leaves develop. Younger leaves produce high levels of C6-aldehydes, mainly composed of hexanal.Subsequently, as the leaves develop, the level of C6-aldehyde formation decreases markedly, followed by an increase with a large shift from hexanal to hexenals. Lipoxygenase and lipolytic acyl hydrolase activity was reduced, and, in contrast, hydroperoxide lyase activity increased. There was little difference in lipoxygenase substrate specificity for linoleic acid and linolenic acid, but hydroperoxide lyase preferentially utilized 13-hydroperoxy-9,11,15-octadecatrienoic acid. In the in vivo lipoxygenase substrate pool, the linoleic acid level declined and the relative level of linolenic acid increased. The change in ratios of linolenic acid to linoleic acid showed a similar trend during soybean leaf development to that of hexenals to hexanal. C6-aldehydes are major volatile compounds produced by injured leaves of many species of plants. C6-aldehydes are formed via the LOX2 pathway (11). When plant leaves are damaged by wounding or freezing, the unsaturated fatty acids linoleic acid and/or linolenic acid can be rapidly dioxygenated by LOX into 13-hydroperoxy fatty acids. These hydroperoxides can be cleaved by HPL to form the C6- ' The investigation reported in this paper ) is in connection with a project of the Kentucky Agricultural Experiment Station and published with approval of the Director. 2Abbreviations: LOX, lipoxygenase; BHT, butylated hydroxytoluene (2,6-di-tert-butyl-p-cresol); DGD, digalactosyldiacylglycerol; FFA, free fatty acid; 17:0, heptadecanoic acid; HPL, hydroperoxide lyase; 13-HPOD, 13-hydroperoxy-9,11-octadecadienoic acid; 9-HPOT, 9-hydroperoxy-9,11,15-octadecatrienoic acid; 13-HPOT, 13-hydroperoxy-9,11,15-octadecatrienoic acid; 18:2, linoleic acid; 18:3, linolenic acid; LAH, lipolytic acyl hydrolase; -L1, a null for LOX 1; -L1L3, a null for LOX 1 and LOX 3; -L2, a null for LOX 2; -L2L3, a null for LOX 2 and LOX 3; -L3, a null for LOX 3; MGD, monogalactosyldiacylglycerol; 18:1, oleic acid; 16:0, palmitic acid; PC, phosphatidylcholine; 18:0, stearic acid; TFA, total fatty acid; TG, triacylglycerol. aldehydes hexanal and/or cis-3-hexenal. Cis-3-hexenal is usually isomerized to trans-2-hexenal both enzymically and nonenzymically. These C6-aldehydes are responsible for the 'green' odor of leaves (11).C6-aldehydes were first reported in green leaves about 80 years ago (1). Although the pathway leading to the formation of C6-compounds in plant leaves has been well understood (11), the control of C6-compound formation in leaves i...

Hexanal Synthesis in Isolated Soy Proteins

“…Kondo et al [52] reported on hydroperoxide lyase activity (also stabilized with DTT) in the enzyme extracts from soybean cotyledons. Other researchers have reported on the activity of hydroperoxide lyase and lipoxygenase enzymes in the seeds and leaves of soybean plants at various stages of growth [53][54][55].…”

Age-Dependent Variations of Volatile Emissions and Inhibitory Activity Toward Botrytis cinerea and Fusarium oxysporum in Tomato Leaves Treated with Chitosan Oligosaccharide

“…Plant volatiles can be influenced by many factors, e.g., stress, growing conditions, elicitors, and developmental stage. In soybeans, levels of C6-aldehydes are high in younger leaves but are decreased markedly as that tissue matures (Zhuang et al 1992). Dudai et al (2001) have Values not followed by the same letter within a column are significantly different at 5% studied the developmental control of monoterpene content and composition in M. fruticosa (L.) Druce and have discovered that the amounts of most compounds increase, while only a few decrease over time.…”

“…Numerous factors can affect the quality and quantity of plant VOCs such as developmental stage, growing conditions, and stress. For example, the release of isoprene and C6-aldehyde from bean leaves depends upon their level of maturity (Kuzma and Fall 1993;Zhuang et al 1992). Furthermore, Staudt et al (1997) have shown that patterns for monoterpene emissions from Pinus pinea (L.) are influenced by seasonal and diurnal factors.…”

Senescence of Broccoli Buds Is Related to Changes in Lipid Peroxidation

“…The significantly increased TBA-RS with decreased CIS hydroperoxides suggests that lipid hydroperoxide synthesis may be a rate-limiting step in the in vivo LP pathway. In fact, several lines of evidence have shown that hydroperoxide synthesis by LOX is a limiting step during c6 aldehyde formation via a LOX-hydroperoxide lyase pathway (Zhuang et al, 1992;Matoba et al, 1985;Sekiya et al, 1984). Lipoxygenase Activity.…”