Westwood J H, Yu X, Foy C L, Cramer C L
Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0331, USA.
Mol Plant Microbe Interact. 1998 Jun;11(6):530-6. doi: 10.1094/MPMI.1998.11.6.530.
Orobanche spp. are angiosperms that live parasitically on the roots of other plants, and are capable of significantly reducing the yield and quality of their crop hosts. We have demonstrated that parasitization by Orobanche induces expression of hmg2, a defense-related isogene of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) in tobacco. Transgenic tobacco plants expressing a construct containing 2.3 kb of the tomato hmg2 gene promoter fused to the beta-glucuronidase (GUS) reporter gene were parasitized by O. aegyptiaca. Expression of the hmg2:GUS construct was detected within 1 day following penetration of the host root by the O. aegyptiaca radicle and was localized to the region immediately around the site of parasite invasion. This expression continued and intensified over the course of O. aegyptiaca development. In addition, the hmg2:GUS expression was induced by secondary parasitization, where secondary roots of O. aegyptiaca contacted the host root at a distance from the primary attachment site. This GUS expression was specific to plants containing the hmg2:GUS construct, and was not observed in control plants transformed with a construct of the cauliflower mosaic virus 35S promoter fused to the GUS gene. These results indicate that Orobanche parasitization initiates rapid and sustained induction of a defense-related gene in the host root.
列当属植物是寄生于其他植物根部的被子植物，能够显著降低其作物寄主的产量和品质。我们已经证明，列当寄生会诱导烟草中hmg2的表达，hmg2是3-羟基-3-甲基戊二酰辅酶A还原酶（HMGR）的一个与防御相关的同基因。用含有与β-葡萄糖醛酸酶（GUS）报告基因融合的2.3 kb番茄hmg2基因启动子构建体转化的转基因烟草植株被埃及列当寄生。在埃及列当胚根穿透寄主根后的1天内就检测到了hmg2:GUS构建体的表达，并且定位在寄生虫入侵部位周围的区域。在埃及列当发育过程中，这种表达持续并增强。此外，hmg2:GUS的表达是由二次寄生诱导的，即埃及列当的次生根在远离初次附着部位的地方与寄主根接触。这种GUS表达对含有hmg2:GUS构建体的植物具有特异性，在用与GUS基因融合的花椰菜花叶病毒35S启动子构建体转化的对照植物中未观察到。这些结果表明，列当寄生在寄主根中引发了与防御相关基因的快速和持续诱导。
