Dumin Walftor, Rostas Michael, Winefield Christopher
Department of Wine Food and Molecular Biosciences, Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln, Christchurch, New Zealand.
Bio-Protection Research Centre, Lincoln University, Lincoln, Christchurch, New Zealand.
Mol Biol Rep. 2018 Jun;45(3):263-277. doi: 10.1007/s11033-018-4159-y. Epub 2018 Feb 9.
Jasmonic acid (JA) is known to be an important phytohormone that orchestrates plant defence mechanisms against a range of herbivores and pathogens. Studies have suggested allene oxide synthase (AOS; E.C 4.2.1.92), the first committed step in JA biosynthesis, is essential for JA biosynthesis, yet clear evidence of its role as a biosynthetic regulatory point is lacking, in the main due to conflicting results derived from transgenic studies. However other studies lend support to a biosynthetic regulatory role for AOS. These studies have suggested that certain amino acid substitutions can increase the biosynthetic capacity of the enzyme and consequently improve pathogen tolerance in plants. To explore the role of AOS in Grapevine we isolated and functionally characterised this enzyme for the first time from Vitis vinifera L. Sauvignon blanc. The cloned AOS consisted of a single 1563 bp open reading frame. Comparative sequence analysis showed that the cloned gene (VvAOS) was highly conserved compared to those from other species. Complementation of an Arabidopsis AOS null mutant (aos) with VvAOS recovered the male sterile mutant phenotype and confirmed its function. Transcript analysis showed that VvAOS was wound responsive in leaves and was detectable in most tissues, with the highest levels of transcript in the mesocarp (pulp) of mature berries. Sub-cellular localisation of the VvAOS protein indicated that VvAOS is associated with the chloroplast membrane. Unexpectedly high levels of VvAOS transcript in complemented aos lines did not lead to predicted increases in JA. We have functionally characterised the sole AOS from Grapevine. Patterns of transcript accumulation in grapevine suggest roles in growth, development as well as an important role for JA in fruit ripening. Expression of VvAOS in Arabidopsis suggest complex epigenetic interactions between transgenic and endogenous AOS alleles, providing a possible explanation for why transgenic studies of AOS have delivered conflicting data pointing to a questionable role of AOS as a key regulatory point in JA biosynthesis.
茉莉酸（JA）是一种重要的植物激素，它能协调植物抵御多种食草动物和病原体的防御机制。研究表明，丙二烯氧化物合酶（AOS；E.C 4.2.1.92）是JA生物合成的第一个关键步骤，对JA生物合成至关重要，但主要由于转基因研究结果相互矛盾，缺乏其作为生物合成调控点作用的明确证据。然而，其他研究支持AOS具有生物合成调控作用。这些研究表明，某些氨基酸取代可以提高该酶的生物合成能力，从而提高植物对病原体的耐受性。为了探究AOS在葡萄中的作用，我们首次从酿酒葡萄品种长相思中分离并对该酶进行了功能表征。克隆的AOS由一个1563 bp的单一开放阅读框组成。比较序列分析表明，与其他物种的基因相比，克隆的基因（VvAOS）高度保守。用VvAOS对拟南芥AOS缺失突变体（aos）进行互补，恢复了雄性不育突变体表型并证实了其功能。转录分析表明，VvAOS在叶片中对伤口有响应，在大多数组织中均可检测到，在成熟浆果的中果皮（果肉）中转录水平最高。VvAOS蛋白的亚细胞定位表明VvAOS与叶绿体膜相关。互补的aos株系中VvAOS转录本水平意外地高，但并未导致JA预期的增加。我们对葡萄中唯一的AOS进行了功能表征。葡萄中转录本积累模式表明其在生长、发育中发挥作用，以及JA在果实成熟中具有重要作用。VvAOS在拟南芥中的表达表明转基因和内源AOS等位基因之间存在复杂的表观遗传相互作用，这可能解释了为什么AOS的转基因研究产生了相互矛盾的数据，表明AOS作为JA生物合成关键调控点的作用存在疑问。
