拟南芥ARS1和ARA1协同调控ABA诱导木栓质生物合成及功能研究

Abscisic acid (ABA) is a universal hormone in higher plants and plays a major role in response to various aspects of stresses, including drought, salt stress, etc. Previous studies have shown that ABA can induce the biological synthesis of suberin. Suberin is deposited as a secondary cell wall, and it can also form a barrier structure, to prevent plants from excessive water loss. The formation of cell wall-based diffusion barriers serves a crucial function in establishing efficient transport pathways. However, the mechanism of ABA-regulated suberin synthesis and then control water transportation is not clear. We found a BAHD family acyltransferase gene, ARS1 (Abscisic acid-related suberin synthesis acyltransferase 1), which can be induced by ABA. To investigate the function of ARS1-related suberin synthesis, we first examined the seed coat permeability of the T-DNA insertion ars1 mutant line using tetrazolium Red, and found that ars1 showed enhanced red staining. These results indicate that ARS1 is essential for seed coat to maintain impermeability. We then tested the reduction of suberin monomer in root. HPLC analysis of the root cell wall revealed that the content of ferulate, ferulate derviates and p-coumarate, the primary phenolics in root, was reduced in ars1 root compared with those wild types. Screening to identify whether proteins can interact with ARS1 or not, we used a yeast of two-hybrid cDNA library from Arabidopsis thaliana, and found that ARS1 interacts strongly with ARA1 (ARS1-related ABCG), encoding an ABCG transporter. Interestingly, ARA1 might be dramatically up-regulated by ABA. In this project, we will use ars1 and ara1 mutants, in combination of the methods of plant physiology, biochemistry, and molecular genetics etc., to explore the molecular mechanism of how ARS1 and ARA1 is involved in ABA-induced suberin synthesis, and analyze the relationship between ABA and the reshaped root endodermis. In addition, we will also explore how to construct the signal transduction network of the ABA-induced suberin synthesis to regulate water transport. Through the implementation of the project, this research not only enriches the ABA signal transduction network, but also provides a new way of understanding how to control water loss under the drought stress.

植物激素脱落酸(ABA)可以参与调节植物抵抗逆境的多种生理反应。已知ABA可诱导木栓质等生物大分子的合成，构成具有保护作用的细胞壁，形成屏障性结构。然而，有关ABA如何通过调节木栓质合成以控制水分运输的机制还不清楚。我们发现一个ABA响应的BAHD酰基转移酶ARS1，当该基因发生突变时，其根部木栓质单体的含量明显降低，并且种皮通透性加大。利用拟南芥酵母文库筛选得到一个与ARS1直接相互作用的ABCG转运蛋白ARA1，该基因受ABA诱导表达量明显上调。本项目拟以ars1和ara1突变体为遗传材料，结合生物化学、分子遗传学等多种生物学方法，探讨ARS1和ARA1参与ABA诱导木栓质合成的分子机理，解析ABA信号与根部内皮层栓质化重塑的关系，构建ABA诱导木栓质合成以调节水分运输的信号转导网络。该项目的实施，不仅丰富了ABA信号转导网络，也将为干旱等逆境胁迫下如何控制植物水分散失提供新途径。

木栓质为一种脂质-酚二聚体生物聚酯，主要沉积在形成有次生细胞壁的植物组织中，作为一种栅栏以控制水分和营养物质的运输，并在植物耐受各种胁迫过程中发挥着重要作用。植物激素ABA参与调节植物抵抗逆境的多种生理反应，可诱导木栓质等生物大分子的合成，构成具有保护作用的细胞壁，形成屏障性结构。然而，有关ABA如何通过调节木栓质合成以控制水分运输或平衡的机制还不清楚。我们利用分子遗传学、细胞生物学、生物化学和植物生理学等多学科技术，发现ABA能明显诱导一个与木栓质合成有关BAHD酰基转移酶基因ARS1（Abscisic acid-related suberin synthesis 1）的表达，当该基因发生突变时，其根部木栓质酚类单体的含量明显降低，并且种皮通透性加大，植株莲座叶直径变小。通过生物信息学分析发现一个与ARS1共表达的ABCG转运蛋白ARA1（ARS1-related ABCG），并利用酵母表达系统分析表明，ARA1可能具有转运ABA和阿魏酸的活性，ARA1及其同源基因ARA2和ARA3协同调控木栓质在组织内的积累，并影响拟南芥种皮的通透性和莲座叶的生长发育。ARS1与ABA信号转导的关键组分OST1相互作用，推测ARS1可能反馈调节OST1的活性，保持ABA诱导下的植物组织适度木栓化，以维持水分的平衡。该项目发展了ABA调节水分平衡的信号转导网络，提出了ARS1与ARA1及其同源基因协同参与ABA诱导木栓质形成过程中的功能，回答了ABA信号与木栓质合成、种皮栓质化重塑以控制水分散失等一些重要的基本生物学问题，为基因工程技术提高植物的水分利用效率开辟了新途径。