Microbial Technology Department, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, India.
Analytical Chemistry Department, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, India.
Physiol Plant. 2021 Dec;173(4):1862-1881. doi: 10.1111/ppl.13528. Epub 2021 Sep 5.
Downy mildew is one of the most serious diseases of Papaver somniferum. Endophytes isolated from different parts of P. somniferum were screened for their ability to enhance resistance against downy mildew caused by the obligate biotrophic oomycete Peronospora meconopsidis. Two endophytes (SMR1 and SMR2) reduced the downy mildew on three P. somniferum genotypes (Sampada, J-16, and I-14). SMR1 (Microbacterium sp.) also enhanced the resistance of P. somniferum against downy mildew under field conditions. The biochemical markers of plant susceptibility under biotic stresses (proline and malondialdehyde) were found to be reduced in P. somniferum upon SMR1 treatment. To understand the mechanisms underlying the enhanced resistance to downy mildew in SMR1 endophyte-treated P. somniferum genotype J-16, we compared the expression profiles using the next-generation RNA sequencing approach between P. somniferum pretreated with SMR1 and untreated endophyte-free control plants following exposure to downy mildew pathogen. Comparative transcriptome analysis revealed differential expression of transcripts belonging to broad classes of signal transduction, protein modification, disease/defense proteins, transcription factors, and phytohormones in SMR1-primed P. somniferum after infection with downy mildew pathogen. Furthermore, enhanced salicylic acid content was observed in SMR1-primed P. somniferum after exposure to downy mildew pathogen. This study sheds light on molecular mechanisms underlying enhanced resistance to downy mildew in SMR1-primed P. somniferum. Finally, we propose that the SA-dependent defense pathway, the hallmark of systemic acquired resistance, is activated in SMR1-primed P. somniferum, triggering the endophyte-induced resistance.
霜霉病是罂粟（Papaver somniferum）最严重的病害之一。本研究从罂粟不同部位分离内生菌，筛选对由专性活体营养卵菌 Peronospora meconopsidis 引起的霜霉病具有抗性的内生菌。两种内生菌（SMR1 和 SMR2）降低了三种罂粟基因型（Sampada、J-16 和 I-14）的霜霉病。SMR1（Microbacterium sp.）也在田间条件下增强了罂粟对霜霉病的抗性。在 SMR1 处理后，发现受生物胁迫影响的植物敏感性生化标志物（脯氨酸和丙二醛）在罂粟中降低。为了了解 SMR1 内生菌处理的 J-16 型罂粟增强对霜霉病抗性的机制，我们比较了 SMR1 预处理和未处理内生菌对照植物在暴露于霜霉病病原体后，使用下一代 RNA 测序方法获得的表达谱。比较转录组分析显示，在 SMR1 预处理的罂粟中，属于信号转导、蛋白质修饰、疾病/防御蛋白、转录因子和植物激素等广泛类别的转录本的表达存在差异，在感染霜霉病病原体后。此外，在暴露于霜霉病病原体后，在 SMR1 预处理的罂粟中观察到水杨酸含量增加。本研究阐明了 SMR1 预处理的罂粟增强对霜霉病抗性的分子机制。最后，我们提出 SMR1 预处理的罂粟中激活了依赖水杨酸的防御途径，这是系统获得性抗性的标志，触发了内生菌诱导的抗性。
