Bate N J, Rothstein S J
Department of Molecular Biology and Genetics, University of Guelph, Ontario, Canada.
Plant J. 1998 Dec;16(5):561-9. doi: 10.1046/j.1365-313x.1998.00324.x.
Six-Carbon (C6-) volatiles, including the aldehydes trans-2-hexenal, hexanal and cis-3-hexenal, as well as their corresponding alcohols, are produced from damaged or wounded plant tissue as a product of the enzymatic activity of hydroperoxide lyase (HPL), a component of the lipoxygenase (LOX) pathway. Aerial treatment of Arabidopsis seedlings with 10 microM concentrations of trans-2-hexenal induces several genes known to be involved in the plant's defense response, including phenylpropanoid-related genes as well as genes of the LOX pathway. Genes encoding the pathogenesis-related proteins PR-1 or PR-2, however, were not induced. Trans-2-hexenal induction thus closely mimics the group of genes induced by methyl jasmonate (MeJA), also a LOX-derived volatile. However, unlike MeJA, trans-2-hexenal did not induce hydroxymethylglutaryl-coenzyme A reductase (HMGR) or thionin2-1. The inductive effect seemed to be limited to C6-related volatiles, as C8-, C9- and other related volatiles did not induce LOX mRNA levels. As has been demonstrated for MeJA, trans-2-hexenal quantitatively reduced wild-type seed germination. Trans-2-hexenal also reduced the germination frequency of the MeJA resistant Arabidopsis mutant, jar1-1, supporting the notion that trans-2-hexenal and MeJA are recognized via different mechanisms. In addition, trans-2-hexenal had a moderate inhibitory effect on root length relative to similar concentrations of MeJA and was approximately 10-fold less effective than MeJA at inducing anthocyanin accumulation in Arabidopsis seedlings. These results suggest that C6-volatiles of the LOX pathway act as a wound signal in plants, but result in a moderate plant response relative to MeJA at both the physiological and molecular level.
六碳（C6-）挥发性物质，包括反式-2-己烯醛、己醛和顺式-3-己烯醛等醛类，以及它们相应的醇类，是植物组织受损或受伤时，由脂氧合酶（LOX）途径的一个组成部分——氢过氧化物裂解酶（HPL）的酶促活性产生的产物。用10微摩尔浓度的反式-2-己烯醛对拟南芥幼苗进行气生处理，可诱导多个已知参与植物防御反应的基因，包括苯丙烷类相关基因以及LOX途径的基因。然而，编码病程相关蛋白PR-1或PR-2的基因并未被诱导。因此，反式-2-己烯醛诱导的基因与茉莉酸甲酯（MeJA）诱导的基因相似，茉莉酸甲酯也是一种由LOX衍生的挥发性物质。然而，与MeJA不同的是，反式-2-己烯醛不会诱导羟甲基戊二酰辅酶A还原酶（HMGR）或硫堇2-1。诱导作用似乎仅限于与C6相关的挥发性物质，因为C8-、C9-和其他相关挥发性物质不会诱导LOX mRNA水平。正如对MeJA所证明的那样，反式-2-己烯醛定量降低了野生型种子的萌发率。反式-2-己烯醛还降低了对MeJA具有抗性的拟南芥突变体jar1-1的萌发频率，这支持了反式-2-己烯醛和MeJA是通过不同机制被识别的观点。此外，相对于相同浓度的MeJA，反式-2-己烯醛对根长有适度的抑制作用，并且在诱导拟南芥幼苗花青素积累方面的效果比MeJA低约10倍。这些结果表明，LOX途径的C6-挥发性物质在植物中作为一种伤口信号，但在生理和分子水平上相对于MeJA会导致适度的植物反应。
