Yuhui Liu

A transcription-aided selection (TAS) strategy is proposed in this paper, which utilizes the positive regulatory roles of genes involved in the plant immunity pathways to screen crops with high disease resistance. Increased evidence has demonstrated that upon pathogen attack, the expression of diverse genes involved in salicylic acid (SA)-mediated SAR are differentially expressed and transcriptionally regulated. The paper discusses the molecular mechanisms of the SA signaling pathway, which plays a central role in plant immunity, and identifies differentially expressed genes (DEGs) that could be targeted for transcriptional detection. We have conducted a series of experiments to test the TAS strategy and found that the level of GmSAGT1 expression is highly correlated with soybean downy mildew (SDM) resistance with a correlation coefficient R2 = 0.7981. Using RT-PCR, we screened 2501 soybean germplasms and selected 26 collections with higher levels of both GmSAGT1 and GmPR1 (Pathogenesis-related proteins1) gene expression. Twenty-three out of the twenty-six lines were inoculated with Peronospora manshurica (Pm) in a greenhouse. Eight showed HR (highly resistant), four were R (resistant), five were MR (moderately resistant), three were S (susceptible), and three were HS (highly susceptible). The correlation coefficient R2 between the TAS result and Pm inoculation results was 0.7035, indicating a satisfactory consistency. The authors anticipate that TAS provides an effective strategy for screening crops with broad-spectrum and long-lasting resistance.

Background: Soybean downy mildew (SDM), caused by Peronospora manshurica (Pm), is a major fungal disease in soybean. To date, little is known regarding the defense mechanism at molecular level and how soybean plants response to Pm infection. In this study, differential gene expression in SDM-resistant (HR) and SDM-susceptible (HS) genotype was analyzed by RNA-seq to identify differentially expressed genes (DEGs) following Pm infection. Results: Of a total of 55,017 genes mapped to the soybean reference genome sequences, 2581 DEGs were identified. Clustering analysis of DEGs revealed that these genes could be grouped into 8 clusters with distinct expression patterns. Functional annotation based on gene ontology (GO) and KEGG analysis indicated they involved in diverse metabolism pathways. Of particular interest were the detected DEGs participating in SA/ROS and JA signalling transduction and plant/pathogen interaction. Conclusion: Totally, 52 DEGs with P value < 0.001 and log(2) fold change > 2 or < - 2 upon fungal inoculation were identified, suggesting they were SDM defense responsive genes. These findings have paved way in further functional characterization of candidate genes and subsequently can be used in breeding of elite soybean varieties with better SDM-resistance.

The evolutionary conserved WD-40 protein PRL1 plays important roles in immunity and development. Here we show that PRL1 is required for the accumulation of microRNAs (miRNAs) and small interfering RNAs (siRNAs). PRL1 positively influences the processing of miRNA primary transcripts (pri-miRNAs) and double-stranded RNAs (dsRNAs). Furthermore, PRL1 interacts with the pri-miRNA processor, DCL1, and the dsRNA processors (DCL3 and DCL4). These results suggest that PRL1 may function as a general factor to promote the production of miRNAs and siRNAs. We also show that PRL1 is an RNA-binding protein and associates with pri-miRNAs in vivo. In addition, prl1 reduces pri-miRNA levels without affecting pri-miRNA transcription. These results suggest that PRL1 may stabilize pri-miRNAs and function as a co-factor to enhance DCL1 activity. We further reveal the genetic interaction of PRL1 with CDC5, which interacts with PRL1 and regulates transcription and processing of pri-miRNAs. Both miRNA and pri-miRNA levels are lower in cdc5 prl1 than those in either cdc5 or prl1. However, the processing efficiency of pri-miRNAs in cdc5 prl1 is similar to that in cdc5 and slightly lower than that in prl1. Based on these results, we propose that CDC5 and PRL1 cooperatively regulate pri-miRNA levels, which results in their synergistic effects on miRNA accumulation, while they function together as a complex to enhance DCL1 activity. PRL1, a conserved WD-40 protein, is required for plant development and immune responses. However, its functional mechanisms are not well understood. Here, we show the positive impact of PRL1 on the accumulation of miRNAs and siRNAs, which are key regulators of plant growth and immunity. PRL1 interacts with multiple DCLs (the processors of miRNAs and siRNAs) and is required for their optimal activities, suggesting that PRL1 acts as a general factor to facilitate the production of miRNAs and siRNAs. In addition, PRL1 is an RNA-binding protein, binds pri-miRNAs in vivo and positively influences the levels of pri-miRNAs levels without affecting the promoter activities of genes encoding pri-miRNAs. These results suggest that PRL1 may also stabilize pri-miRNAs. We further show that RPL1 and its interactor CDC5 (a DNA-binding protein) synergistically regulate pri-miRNA levels, resulting in enhanced effects on miRNA accumulation, although they function together as a complex to facilitate DCL1 activity.