Reddy P S, Kumar T C, Reddy M N, Sarada C, Reddanna P
School of Life Sciences, University of Hyderabad, Hyderabad, India.
Biochim Biophys Acta. 2000 Jan 17;1483(2):294-300. doi: 10.1016/s1388-1981(99)00191-2.
Lipoxygenases in plants have been implicated in the activation of defense responses against injury/infection. Pathogen-derived polyunsaturated fatty acids, such as arachidonic acid, eicosapentaenoic acid and their metabolites have been shown to elicit defense responses against pathogen infection in plants. However, not much is known about the role of host-derived fatty acids and their metabolites in plant defense responses. In this study, isolation and characterisation of endogenous lipoxygenase metabolites formed in potato tubers in response to injury/infection was undertaken. While 9-hydroperoxyoctadecadienoic acid (9-HPODE), derived from octadecdienoic acid (linoleic acid) is the major lipoxygenase product formed in control potato tubers, 9-hydroperoxyoctadecatrienoic acid (9-HPOTrE), derived from octadecatrienoic acid (alpha-linolenic acid) is the major lipoxygenase product formed in potato tubers in response to injury or infection with Rhizoctonia bataticola. As a result, the relative ratio of 9-HPODE to 9-HPOTrE showed a shift from 4:1 in control to 1:2 and 1:4.5 in injured and infected potato tubers respectively. From this study, it is proposed that lipoxygenase metabolites of octadecadienoic acid may be involved in physiological responses under control conditions, while octadecatrienoic acid metabolites are mediating the defense responses. This forms the first report on the differential formation of endogenous lipoxygenase products in potato tubers under control and stress conditions.
植物中的脂氧合酶与针对损伤/感染的防御反应激活有关。病原体衍生的多不饱和脂肪酸，如花生四烯酸、二十碳五烯酸及其代谢产物，已被证明能引发植物针对病原体感染的防御反应。然而，关于宿主衍生的脂肪酸及其代谢产物在植物防御反应中的作用，我们了解得并不多。在本研究中，我们对马铃薯块茎在响应损伤/感染时形成的内源性脂氧合酶代谢产物进行了分离和表征。虽然源自十八碳二烯酸（亚油酸）的9-氢过氧十八碳二烯酸（9-HPODE）是对照马铃薯块茎中形成的主要脂氧合酶产物，但源自十八碳三烯酸（α-亚麻酸）的9-氢过氧十八碳三烯酸（9-HPOTrE）是马铃薯块茎在响应损伤或受到立枯丝核菌感染时形成的主要脂氧合酶产物。结果，9-HPODE与9-HPOTrE的相对比例从对照中的4:1分别转变为受伤和感染马铃薯块茎中的1:2和1:4.5。从这项研究中可以提出，十八碳二烯酸的脂氧合酶代谢产物可能参与对照条件下的生理反应，而十八碳三烯酸代谢产物则介导防御反应。这是关于对照和胁迫条件下马铃薯块茎内源性脂氧合酶产物差异形成的首次报道。
