Mechanisms of natural and transgenic auxinic herbicide resistance

辛酸除草剂(如2，4-D、敌草畏)是第一批选择性有机除草剂，已在农业上使用了60多年，主要用于选择性防除谷类作物中的阔叶杂草。它们使现代农业发生了革命性的变化。如果由于严重的杂草抗性而取消使用除草剂，加拿大农民每年的经济损失估计超过3.5亿美元，其中约2.5亿美元是由于农作物损失，1亿美元是替代除草剂的额外费用。消费者在第一年的成本约为3000-3300万美元，到第六年将增加到3亿美元。这些除草剂被归类为吲哚-3-乙酸(IAA)的模拟物，吲哚-3-乙酸是一种天然植物激素，也被称为生长素。生长素几乎涉及植物生长发育的方方面面。对生长素类除草剂的抗药性有所增加。其中抗性最强的杂草之一是野生芥菜(S.arvensis L.)在马尼托巴省用生长素除草剂处理了10多年的田野中发现的生物型。我的团队是第一个从生理、生化和遗传上描述这种抗药性(R)生物型的人，从而加深了我们对生长素除草剂作用机制(S)的理解，从而也加深了我们对生长素作用机制的理解。本研究的主要目的有两个：(1)鉴定野生芥菜(S.arvensis)对生长素除草剂抗性的基因；(2)在烟草和拟南芥中开发基于抗体(Ab)的生长素除草剂抗性，并表达用于生长素免疫调节的抗IAA抗体。通过本研究获得的知识可能鉴定一个新的生长素受体类别，可能提供对抗生长素除草剂抗性的策略，允许开发新的作物抗除草剂机制和新的可选择的标记用于转基因植物的生产，以及用于研究更全面地了解生长素除草剂和生长素的新型生理试剂。此外，在植物中表达针对小分子的抗体可能使这一机制发展成为在植物中建立基于抗体的环境污染物抗性的实用模型，用于污染场地的生物修复。

Auxinic herbicides (e.g. 2,4-D, dicamba) were the first selective organic herbicides developed and have been used in agriculture for over 60 years primarily for the selective control of broadleaf weeds in cereal crops. They have revolutionized modern agriculture. If their use was eliminated because of severe weed resistance the total economic loss to Canadian farmers is estimated to be over $350 M/year, consisting of approximately $250 M due to crop loss and $100 M for the additional cost of replacement herbicides. The cost to consumers would be ca. $30-33 M in the first year, increasing to $300 M by year six. These herbicides are classified as mimics of indole-3-acetic acid (IAA), the natural plant hormone also known as auxin. Auxin has been implicated in virtually all aspects of plant growth and development. The incidence of auxinic herbicide resistance has increased. One of the most resistant weeds is a wild mustard (S. arvensis L.) biotype found in a Manitoba field treated with auxinic herbicides for over 10 years. My group was the first to characterize this resistant (R) biotype physiologically, biochemically, and genetically, thus furthering our understanding of the mechanism(s) of action of auxinic herbicides, and hence the mechanisms of action of auxin. The major goals of this research proposal are twofold: (1) identification of the gene responsible for auxinic herbicide resistance in wild mustard (S. arvensis), and (2) develop antibody (Ab)-based auxinic herbicide resistance, and expression of an anti-IAA Ab for auxin immunomodulation, in tobacco and Arabidopsis plants.  Knowledge gained from this research may identify a new auxin receptor class, may provide strategies to combat auxinic-herbicide resistance, allow development of novel herbicide resistance mechanisms for crop plants and new selectable markers for use in the production of transgenic plants, and novel physiological reagents for use in research towards a more complete understanding of auxinic herbicides and auxins.  Furthermore, expression of Abs against small molecules in plants may allow development of this mechanism as a practical model for creating Ab-based environmental contaminant resistance in plants for bioremediation of contaminated sites.