柚皮素甲基转移酶在玉米抗病蛋白Rp1-D21介导的防卫反应中的功能研究

Identification of new disease resistance genes is very important for crop genetic improvement. The plant flavonoid antitoxin, sakuranetin, is one of the major antitoxins and plays important roles in resistance to pathogen infection. Previous studies in rice showed that sakuranetin was synthesized by naringenin O-methyltransferase (NOMT) using naringenin as substrate. However, the function of NOMT in plant disease resistance has not been reported. Our preliminary results showed that the homolog of NOMT in maize (ZmNOMT) could suppress Rp1-D21-mediated HR through protein interaction, but the mechanism of how ZmNOMT regulates HR is unclear.We speculate that ZmNOMT could contribute to disease resistance in maize. In this work, we will construct transgenic maize plants including ZmNOMT over-expression and knocking-out lines. These materials will be hybridized to Rp1-D21 mutant, to study the function of ZmNOMT in regulating Rp1-D21-mediated HR and disease resistance in maize. We will also measure the content of various metabolic substances in the flavonoids biosynthesis pathway from wild type and different transgenic maize plants by metabonomics method. We will systematically investigate the molecular and biochemical mechanism of how ZmNOMT regulates Rp1-D21-mediated HR. This work will help to understand the molecular mechanism of ZmNOMT in regulating Rp1-D21-mediated HR and disease defense response and it will provide new disease resistance genes for the genetic improvement of maize and other crops.

鉴定作物抗病新基因对作物遗传改良至关重要。植物黄酮类抗毒素-樱花木素(sakuranetin)是最主要的抗毒素之一，在植物抗病过程中发挥重要作用。樱花木素由柚皮素甲基转移酶(NOMT)催化柚皮素产生，但NOMT在植物抗病中的功能尚未见报道。申请人在前期工作中首次发现玉米ZmNOMT通过蛋白互作抑制抗病蛋白Rp1-D21介导的自主HR表型，但其作用机理有待研究。推测NOMT作为一种潜在的抗病基因，在玉米抗病防卫反应中发挥重要作用。本项目将通过玉米转基因和杂交鉴定ZmNOMT在调控HR和玉米抗病中的作用；利用代谢组学检测转基因玉米黄酮类物质生物合成途径中各代谢物质的含量变化；结合分子生物学和生化技术探究该基因调控Rp1-D21介导HR的分子机制。本研究将阐明ZmNOMT在抗病蛋白Rp1-D21介导HR以及在玉米系统抗病防卫反应中的功能和作用机理，为玉米及其它作物的遗传改良提供新的抗病基因资源。

鉴定作物抗病新基因对作物遗传改良至关重要。柚皮素在植物抗病过程中发挥重要作用。柚皮素甲基转移酶(NOMT)能够催化柚皮素产生樱花木素，但NOMT在植物抗病中的功能未见报道。本研究通过烟草瞬时表达系统和玉米转基因材料发现，ZmNOMT能够通过与Rp1-D21的CCD21结构域发生蛋白质相互作用，抑制Rp1-D21介导的HR反应。体外实验表明，ZmNOMT具有柚皮素甲基转移酶活性。过表达ZmNOMT导致玉米对常见病害大斑病、小斑病的抗病性降低。通过上述结果，本研究初步阐明了ZmNOMT在抗病蛋白Rp1-D21介导HR以及在玉米系统抗病防卫反应中的功能和作用机理，为玉米及其它作物的遗传改良提供了新的抗病基因资源。