Gma-miR408 Enhances Soybean Cyst Nematode Susceptibility by Suppressing Reactive Oxygen Species Accumulation.

Soybean cyst nematode (SCN, Heterodera glycine) is a serious damaging disease in soybean worldwide, thus resulting in severe yield losses. MicroRNA408 (miR408) is an ancient and highly conserved miRNA involved in regulating plant growth, development, biotic and abiotic stress response. Here, we analyzed the evolution of miR408 in plants and verified four miR408 members in Glycine max. In the current research, highly upregulated gma-miR408 expressing was detected during nematode migration and syncytium formation response to soybean cyst nematode infection. Overexpressing and silencing miR408 vectors were transformed to soybean to confirm its potential role in plant and nematode interaction. Significant variations were observed in the MAPK signaling pathway with low OXI1, PR1, and wounding of the overexpressing lines. Overexpressing miR408 could negatively regulate soybean resistance to SCN by suppressing reactive oxygen species accumulation. Conversely, silencing miR408 positively regulates soybean resistance to SCN. Overall, gma-miR408 enhances soybean cyst nematode susceptibility by suppressing reactive oxygen species accumulation.

Functional Characterization of Ubiquitination Genes in the Interaction of Soybean-Heterodera glycines.

Ubiquitination is a kind of post-translational modification of proteins that plays an important role in plant response to biotic and abiotic stress. The response of soybean GmPUB genes to soybean cyst nematode (SCN, Heterodera glycines) infection is largely unknown. In this study, quantitative real-time PCR (qRT-PCR) was performed to detect the relative expression of 49 GmPUB genes in susceptible cultivar William 82 and resistant cultivar Huipizhi after SCN inoculation. The results show that GmPUB genes responded to cyst nematode infection at 1 day post-inoculation (dpi), 5 dpi, 10 dpi and 15 dpi. The expression levels of GmPUB16A, GmPUB20A, GmCHIPA, GmPUB33A, GmPUB23A and GmPUB24A were dramatically changed during SCN infection. Furthermore, functional analysis of these GmPUB genes by overexpression and RNAi showed that GmPUB20A, GmPUB33A and GmPUB24A negatively regulated soybean resistance under SCN stress. The results from our present study provide insights into the complicated molecular mechanism of the interaction between soybean and SCN.

Soybean miR159-GmMYB33 Regulatory Network Involved in Gibberellin-Modulated Resistance to Heterodera glycines.

Soybean cyst nematode (SCN, Heterodera glycines) is an obligate sedentary biotroph that poses major threats to soybean production globally. Recently, multiple miRNAome studies revealed that miRNAs participate in complicated soybean-SCN interactions by regulating their target genes. However, the functional roles of miRNA and target genes regulatory network are still poorly understood. In present study, we firstly investigated the expression patterns of miR159 and targeted GmMYB33 genes. The results showed miR159-3p downregulation during SCN infection; conversely, GmMYB33 genes upregulated. Furthermore, miR159 overexpressing and silencing soybean hairy roots exhibited strong resistance and susceptibility to H. glycines, respectively. In particular, miR159-GAMYB genes are reported to be involve in GA signaling and metabolism. Therefore, we then investigated the effects of GA application on the expression of miR159-GAMYB module and the development of H. glycines. We found that GA directly controls the miR159-GAMYB module, and exogenous GA application enhanced endogenous biologically active GA1 and GA3, the abundance of miR159, lowered the expression of GmMYB33 genes and delayed the development of H. glycines. Moreover, SCN infection also results in endogenous GA content decreased in soybean roots. In summary, the soybean miR159-GmMYB33 module was directly involved in the GA-modulated soybean resistance to H. glycines.

Metabolomic Analyses Reveal That IAA from Serratia marcescens Lkbn100 Promotes Plant Defense during Infection of Fusarium graminearum in Sorghum.

Global sorghum production has been significantly reduced due to the occurrence of sorghum root rot caused by the fungus Fusarium graminearum. The utilization of biocontrol microorganisms has emerged as an effective strategy. However, the underlying mechanisms remain unclear. Therefore, the aim of this study was to investigate the effectiveness of biocontrol bacteria in inducing sorghum resistance against sorghum root rot and explore the potential induced resistance mechanisms through metabolomics analysis. The results revealed that the biocontrol bacteria Lnkb100, identified as Serratia marcescens (GenBank: PP152264), significantly enhanced the resistance of sorghum against sorghum root rot and promoted its growth, leading to increased seed weight. Targeted metabolomics analysis demonstrated that the highest concentration of the hormone IAA (indole-3-acetic acid) was detected in the metabolites of Lnkb100. Treatment with IAA enhanced the activity of disease-related enzymes such as SOD, CAT, POD and PPO in sorghum, thereby improving its resistance against sorghum root rot. Further untargeted metabolomic analysis revealed that IAA treatment resulted in higher concentrations of metabolites involved in the resistance against F. graminearum, such as geniposidic acid, 5-L-Glutamyl-taurine, formononetin 7-O-glucoside-6″-O-malonate, as well as higher concentrations of the defense-related molecules volicitin and JA. Additionally, "secondary bile acid biosynthesis" and "glycerophospholipid metabolism" pathways were found to play significant roles in the defense response of sorghum against fungal infection. These findings provide a reliable theoretical basis for utilizing biocontrol microorganisms to control sorghum root rot.

Transcriptome Analysis of GmPUB20A Overexpressing and RNA-Interferencing Transgenic Hairy Roots Reveals Underlying Negative Role in Soybean Resistance to Cyst Nematode.

Ubiquitination genes are key components of plant responses to biotic stress. GmPUB20A, a ubiquitination gene, plays a negative role in soybean resistance to soybean cyst nematode (SCN). In this study, we employed high-throughput sequencing to investigate transcriptional changes in GmPUB20A overexpressing and RNA-interfering transgenic hairy roots. Totally, 7661 differentially expressed genes (DEGs) were identified. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that DEGs were significantly enriched in disease resistance and signal transduction pathways. In addition, silencing Glyma.15G021600 and Glyma.09G284700 by siRNA, the total number of nematodes was decreased by 33.48% and 27.47% than control plants, respectively. Further, GUS activity and reactive oxygen species (ROS) assays revealed that GmPUB20A, Glyma.15G021600, and Glyma.09G284700 respond to SCN parasitism and interfere with the accumulation of ROS in plant roots, respectively. Collectively, our study provides insights into the molecular mechanism of GmPUB20A in soybean resistance to SCN.

Genome-wide identification of small interfering RNAs from sRNA libraries constructed from soybean cyst nematode resistant and susceptible cultivars.

Plant small-RNAs regulate various biological processes by manipulating the expression of target genes at the transcriptional and post-transcriptional levels. However, little is known about the response and the functional roles of sRNAs, particularly small-interfering RNAs (siRNAs), in the soybean-soybean cyst nematode interaction. In this study, siRNA data from 24 sRNA libraries constructed from SCN-infected and non-SCN-infected resistant and susceptible soybean roots were analysed in silico. A total of 26 novel siRNAs including 17 phasiRNAs and 9 nat-siRNAs, as well as two phasiRNAs that were differentially expressed (DE) in three comparisons, were identified. Then, using qRT-PCR, the expression of majority of siRNAs was found to be downregulated after SCN infection, and the expression patterns of DE siRNAs were confirmed. Further functional annotation analyses revealed that the target genes of these siRNA were highly related to disease resistance, which included the genes coding for the NB-ARC domain, leucine-rich repeats, and Hs1pro-1 homologous proteins. Overall, the present research identified novel siRNAs and annotated their target genes, thereby laying the foundation for deciphering the roles of siRNAs in the soybean-SCN interaction.

Soybean root transcriptome profiling reveals a nonhost resistant response during Heterodera glycines infection.

Heterodera glycines (soybean cyst nematode, SCN) is one of the most devastating pathogens of soybean worldwide. The compatible and in compatible interactions between soybean and SCN have well documented. Nevertheless, the molecular mechanism of a nonhost resistant response in soybean against SCN infection remains obscure. Toward this end, a global transcriptional comparison was conducted between susceptible and resistant reactions of soybean roots infected by taking advantage of finding a new pathotype of SCN (SCNT). The soybean cultivar Lee, which exhibits resistant to SCNT and susceptible to HG 1.2.3.4.7 (SCNs) was utilized in the expriments. The results highlighted a nonhost resistant response of soybean. Transcriptome analysis indicated that the number of differentially expressed genes (DEGs) in the resistant interaction (3746) was much larger than that in the susceptible interaction (602). A great number of genes acting as intrinsic component of membrane, integral component of membrane, cell periphery and plasma membrance were remarkably enriched only in the resistant interaction, while the taurine and hypotaurine, phenylpropanoid pathway, plant-pathogen interaction and transcript factors were modulated in both interactions. This is the first study to examine genes expression patterns in a soybean genotype in response to invasion by a virulent and avirulent SCN population at the transcriptional level, which will provide insights into the complicate molecular mechanism of the nonhost resistant interaction.