French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel.
Boyce Thompson Institute, 533 Tower Road, Ithaca, NY, 14853, USA.
Plant Mol Biol. 2022 Jul;109(4-5):533-549. doi: 10.1007/s11103-021-01239-4. Epub 2022 Jan 12.
A combined transcriptomic and metabolic analysis of Setaria viridis leaves responding to aphid infestation was used to identify genes related to serotonin biosynthesis. Setaria viridis (green foxtail), a short life-cycle C4 plant in the Poaceae family, is the wild ancestor of Setaria italica (foxtail millet), a resilient crop that provides good yields in dry and marginal land. Although S. viridis has been studied extensively in the last decade, the molecular mechanisms of insect resistance in this species remain under-investigated. To address this issue, we performed a metabolic analysis of S. viridis and discovered that these plants accumulate the tryptophan-derived compounds tryptamine and serotonin. To elucidate the defensive functions of serotonin, Rhophalosiphum padi (bird cherry-oat aphids) were exposed to this compound, either by exogenous application to the plant medium or with artificial diet bioassays. In both cases, exposure to serotonin increased aphid mortality. To identify genes that are involved in serotonin biosynthesis, we conducted a transcriptome analysis and identified several predicted S. viridis tryptophan decarboxylase (TDC) and tryptamine 5-hydroxylase (T5H) genes. Two candidate genes were ectopically expressed in Nicotiana tabacum, where SvTDC1 (Sevir.6G066200) had tryptophan decarboxylase activity, and SvT5H1 (Sevir.8G219600) had tryptamine hydroxylase activity. Moreover, the function of the SvTDC1 gene was validated using virus-induced gene silencing in S. italica, which caused a reduction in serotonin levels. This study provides the first evidence of serotonin biosynthesis in Setaria leaves. The biosynthesis of serotonin may play an important role in defense responses and could prove to be useful for developing more pest-tolerant Setaria italica cultivars.
对受蚜虫侵害的绿色狗尾草叶片进行的转录组和代谢联合分析，用于鉴定与血清素生物合成相关的基因。绿色狗尾草（绿色狐尾草）是禾本科黍属的一种短生命周期 C4 植物，是黍属（谷子）的野生祖先，是一种适应性强的作物，在干旱和边缘土地上能提供良好的产量。尽管在过去十年中对绿色狗尾草进行了广泛的研究，但该物种的抗虫分子机制仍未得到充分研究。为了解决这个问题，我们对绿色狗尾草进行了代谢分析，发现这些植物积累色氨酸衍生的化合物色胺和血清素。为了阐明血清素的防御功能，我们将麦二叉蚜（Rhopalosiphum padi）暴露于该化合物中，无论是通过向植物培养基中外源添加还是通过人工饮食生物测定。在这两种情况下，暴露于血清素都会增加蚜虫的死亡率。为了鉴定参与血清素生物合成的基因，我们进行了转录组分析，鉴定出了几个预测的绿色狗尾草色氨酸脱羧酶（TDC）和色胺 5-羟化酶（T5H）基因。两个候选基因在烟草中异位表达，其中 SvTDC1（Sevir.6G066200）具有色氨酸脱羧酶活性，SvT5H1（Sevir.8G219600）具有色胺羟化酶活性。此外，SvTDC1 基因的功能通过在谷子中使用病毒诱导的基因沉默进行了验证，这导致血清素水平降低。本研究首次提供了血清素在狗尾草叶片中生物合成的证据。血清素的生物合成可能在防御反应中发挥重要作用，并可能被证明对开发更能耐受害虫的谷子品种有用。
