Key Laboratory of Horticultural Plant Biology of Ministry of Education, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China.
BMC Plant Biol. 2011 Mar 28;11:55. doi: 10.1186/1471-2229-11-55.
Enormous work has shown that polyamines are involved in a variety of physiological processes, but information is scarce on the potential of modifying disease response through genetic transformation of a polyamine biosynthetic gene.
In the present work, an apple spermidine synthase gene (MdSPDS1) was introduced into sweet orange (Citrus sinensis Osbeck 'Anliucheng') via Agrobacterium-mediated transformation of embryogenic calluses. Two transgenic lines (TG4 and TG9) varied in the transgene expression and cellular endogenous polyamine contents. Pinprick inoculation demonstrated that the transgenic lines were less susceptible to Xanthomonas axonopodis pv. citri (Xac), the causal agent of citrus canker, than the wild type plants (WT). In addition, our data showed that upon Xac attack TG9 had significantly higher free spermine (Spm) and polyamine oxidase (PAO) activity when compared with the WT, concurrent with an apparent hypersensitive response and the accumulation of more H₂O₂. Pretreatment of TG9 leaves with guazatine acetate, an inhibitor of PAO, repressed PAO activity and reduced H₂O₂ accumulation, leading to more conspicuous disease symptoms than the controls when both were challenged with Xac. Moreover, mRNA levels of most of the defense-related genes involved in synthesis of pathogenesis-related protein and jasmonic acid were upregulated in TG9 than in the WT regardless of Xac infection.
Our results demonstrated that overexpression of the MdSPDS1 gene prominently lowered the sensitivity of the transgenic plants to canker. This may be, at least partially, correlated with the generation of more H₂O₂ due to increased production of polyamines and enhanced PAO-mediated catabolism, triggering hypersensitive response or activation of defense-related genes.
大量研究表明，多胺参与了多种生理过程，但关于通过遗传转化多胺生物合成基因来改变疾病反应的潜力的信息却很少。
本研究通过农杆菌介导的胚性愈伤组织转化，将苹果亚精胺合酶基因（MdSPDS1）导入甜橙（Citrus sinensis Osbeck 'Anliucheng'）。两个转基因株系（TG4 和 TG9）在转基因表达和细胞内多胺含量上存在差异。针刺接种表明，与野生型植物（WT）相比，转基因株系对柑橘溃疡病病原菌（Xanthomonas axonopodis pv. citri，Xac）的敏感性较低。此外，我们的数据表明，在 Xac 攻击下，TG9 中的游离腐胺（Spm）和多胺氧化酶（PAO）活性显著高于 WT，同时伴随着明显的过敏反应和更多 H₂O₂的积累。用 PAO 抑制剂乙酰氧肟酸预处理 TG9 叶片，抑制了 PAO 活性，减少了 H₂O₂的积累，当两者都受到 Xac 挑战时，比对照表现出更明显的症状。此外，无论是否感染 Xac，TG9 中参与合成病程相关蛋白和茉莉酸的大多数防御相关基因的 mRNA 水平均高于 WT。
我们的结果表明，MdSPDS1 基因的过表达显著降低了转基因植物对溃疡病的敏感性。这可能至少部分与由于多胺的产生增加和增强的 PAO 介导的分解代谢导致的更多 H₂O₂的产生有关，从而触发过敏反应或激活防御相关基因。
