寄主植物间通过菟丝子传递干旱系统性信号的研究

Dodders (Cuscuta spp.) are a typical parasite plant, which lacks of roots and leaves. Stems of dodders twine around the host plants and develop a special organ called haustorium, which transport nutrients from host plants. In nature, dodder could bridge connect different hosts together, forming dodder-connected plant clusters. Recent research has shown that dodders can not only retrieve nutrition from host plants, but also transport macromolecules such as mRNAs, proteins, and even viruses. Drought is an important of abiotic stress, and when roots sense soil moisture deficiency, they communicate with shoots with certain systemic signals, in order to coordinate the responses in different parts of a plant. When experiencing stress, how dodder-connected plant clusters respond is interesting to explore. Our previous experiments found simulated drought treated Arabidopsis induced dodder connected adjacent Arabidopsis abscisic acid (ABA) levels. We hypothesize that by dodder connections, different host plants in the plant clusters can communicate and interact. We plan to use dodder bridge connected host plants as a model to explore the communication and interaction between different hosts in response to drought stress. The physiological changes of the non-drought-treated hosts will be examined, after the connected hosts are treated with drought, and we will also use ABA biosynthesis and receptor mutants of Arabidopsis to study whether ABA is involved in drought-induced systemic signaling between plants. This project will provide valuable information for understanding the interaction between dodders and hosts, the communications among hosts connected by dodders, and will also shed light on the nature of the drought-induced systemic signals.

菟丝子是很常见的寄生植物，无根和叶片，完全不能自养，必须从寄主获得营养物质而生活。菟丝子通过产生吸器与寄主的维管系统融合汲取营养，还可以转运mRNA、蛋白质甚至病毒等大分子。菟丝子经常同时寄生多个寄主，将其相互连接，形成“天然嫁接”的植物微群落。干旱是重要的非生物胁迫之一，植物通过系统性信号对地上部分与根系部分进行生长发育的协调，从而适应干旱胁迫。我们发现模拟干旱处理拟南芥可以诱导菟丝子连接的邻近拟南芥脱落酸（ABA）水平，因此微群落中的寄主之间很可能通过菟丝子的连接而产生通讯和互作。我们拟以菟丝子连接的多个寄主为模型，通过对单个寄主进行干旱胁迫，研究其他寄主的生理变化，对该植物微群落应对干旱的机制进行探讨，同时通过使用拟南芥ABA合成和受体突变体作为寄主植物，探讨干旱系统性信号的传递机制。本项目将为了解菟丝子与寄主间的互作、菟丝子连接的寄主间的通讯，以及植物抗旱系统性信号提供重要信息。

干旱是自然界中影响植物生长的重要因素，严重地影响农作物的产量。菟丝子是否可以在不同的寄主间转运干旱胁迫诱导的系统性信号？系统学信号背后的信号分子是什么？这些系统性信号的转运是否会影响植物的抗旱性？这些问题目前都尚不清楚。本研究利用田野菟丝子(Cuscuta campestris)与黄瓜(Cucumis sativus L.)为互作对象，建立了黄瓜-菟丝子-黄瓜的寄生体系，研究干旱诱导的系统性信号是否可以通过菟丝子从一株黄瓜寄主转运到另一株黄瓜寄主，并影响黄瓜寄主的生理状态。结果表明干旱诱导的系统性信号可以通过菟丝子在两株黄瓜寄主之间进行双向转运，并影响寄主的脱落酸（ABA）、茉莉酸（JA）、茉莉酸异亮氨酸（JA-Ile）含量以及磷脂酶、ABA相关基因的表达水平，证明了菟丝子可以介导干旱胁迫性信号传递这一现象。.本研究采用温室实验对传递信号背后的生态意义进行了探讨，通过比较提前接受过干旱胁迫信号的宿主植物和没有接受的宿主的耐旱性，发现接受过干旱胁迫信号的宿主在耐旱实验中表现出更好的生长，但没有接收过干旱胁迫信号的宿主叶绿素含量减少、电解质渗透率升高、细胞死亡增加。这些结果表明干旱诱导的系统学信号在生理水平影响了菟丝子连接的黄瓜宿主的耐旱性，暗示菟丝子具有潜在帮助宿主应对干旱的生态意义。.最后，本研究用遗传学方法对干旱胁迫信号传递机制进行了研究。通过使用拟南芥的ABA的受体突变体(pyr1/pyl1/pyl4)或独脚金内酯受体（SL）的受体突变体(d14)作为传递植物，发现ABA和水杨酸（SA）含量在对照组和处理组之间存在差异。表明ABA和SL均可能参与了植物间干旱诱导的系统性信号的调控过程。.本研究揭示了干旱胁迫诱导的系统性信号可以在不同的寄主中转运。一方面揭示了干旱胁迫诱导的系统性信号在不同的植物间长距离的转运，而且也说明了这些可移动信号的生态学角色，同时创新性的用植物间体系对干旱胁迫诱导系统性信号传递过程中的潜在机制进行了探索，这些研究将加深我们对干旱胁迫诱导系统性信号传递过程的了解。