Background

Spotted leaf mutants show typical necrotic lesions that appear spontaneously in the absence of any pathogen attack. These mutants are often characterized to exhibit programmed cell death (PCD) and activation of plant defense responses resulting in enhanced disease resistance to multiple pathogens. Here, we reported a novel spotted-leaf mutant, spl40 that showed enhanced disease resistance response.

Results

Initially lesions appeared at leaf tips during seedling stage and gradually covered the whole leaf at the tillering stage. The lesion development was light-dependent. spl40 showed obvious cell death at and around the lesion, and burst of reactive oxygen species (ROS) was accompanied by disturbed ROS scavenging system. Photosynthetic capacity was compromised as evidenced by significant reductions in chlorophyll content, important photosynthesis parameters and downregulated expression of photosynthesis-related genes which ultimately led to poor performance of major agronomic traits. spl40 exhibited enhanced resistance to 14 out of 16 races of bacterial blight pathogen of rice, caused by Xanthomonas oryzae pv. oryzae, most probably though activation of SA and JA signaling pathways, owing to upregulated expression of SA and JA signaling genes, though the exact mechanism remain to be elucidated. The spotted-leaf phenotype was controlled by a novel single recessive nuclear gene. Genetic mapping combined with high throughput sequencing analysis identified Os05G0312000 as the most probable candidate gene. Sequencing of ORF revealed a single SNP change from C to T that resulted in non-synonymous change in amino acid residue from leucine to phenylalanine. Interestingly, the complementation plants did not display lesions before heading but showed lesions at the heading stage and the transgenic T₁ progenies could be classified into 3 categories based on their lesion intensity, indicating the complex genetic nature of the spl40 mutation.

Conclusion

The results obtained here clearly show that genes related to defense and PCD were upregulated in accordance with enhanced disease resistance and occurrence of PCD, whereas the photosynthetic capacity and overall ROS homeostasis was compromised in spl40. Our data suggest that a novel spotted-leaf mutant, spl40, would help to elucidate the mechanism behind lesion development involving programmed cell death and associated defense responses.

中文翻译：

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鉴定并鉴定了具有增强的细菌白叶枯病抗性的斑点叶突变体spl40。

背景

发现的叶突变体显示出典型的坏死性病变，在没有任何病原体侵袭的情况下会自发出现。这些突变体的特征通常表现为程序性细胞死亡（PCD）和植物防御反应的激活，导致对多种病原体的抗病性增强。在这里，我们报道了一种新型的斑点叶突变体spl40，该突变体显示出增强的抗病性反应。

结果

在苗期，病害最初出现在叶尖，在分the期逐渐覆盖整个叶。病变发展是光依赖性的。spl40在病变处及其周围显示出明显的细胞死亡，并且活性氧（ROS）的爆发伴随着ROS清除系统的干扰。叶绿素含量的显着降低，重要的光合作用参数以及光合作用相关基因的表达下调证明了光合能力受到损害，最终导致主要农艺性状表现不佳。spl40显示出对由水稻黄单胞菌（Xanthomonas oryzae pv）引起的16种水稻白叶枯病病原菌中的14种具有增强的抗性。水稻由于SA和JA信号转导基因的表达上调，最有可能通过激活SA和JA信号转导通路，尽管确切的机制尚待阐明。点叶表型是由一个新的单一隐性核基因控制的。遗传作图结合高通量测序分析确定Os05G0312000是最可能的候选基因。ORF的测序揭示了一个单核苷酸多态性从C到T的变化，导致氨基酸残基从亮氨酸到苯丙氨酸的非同义变化。有趣的是，互补植物在抽穗前并未表现出病害，而在抽穗期却表现出病害，根据其病灶强度，转基因T ₁后代可分为3类，这表明补体植物具有复杂的遗传特性。spl40突变。

结论

此处获得的结果清楚地表明，与抗病性和PCD相关的基因根据增强的抗病性和PCD的发生而上调，而在spl40中光合能力和总体ROS稳态受到损害。我们的数据表明，新型斑点叶突变体spl40将有助于阐明涉及程序性细胞死亡和相关防御反应的病变发展背后的机制。