Although pathogens such as nematodes are known to hijack nutrients from host plants, the mechanisms whereby nematodes obtain sugars from plants remain largely unknown. To determine the effects of nematode infection on host plant sugar allocation, soluble sugar (fructose, glucose, sucrose) content was investigated using high-performance liquid chromatography with refractive index detection and was found to increase significantly in tomato (Solanum lycopersicum, Sl) leaves and roots during early infection by root-knot nematodes (RKNs). To further analyze whether sugar transporters played a role in this process, the expression levels of sucrose transporter (SUT/SUC), Sugars Will Eventually be Exported Transporter (SWEET), tonoplast monosaccharide transporter (TMT), and vacuolar glucose transporter (VGT) gene family members were examined by qRT-PCR analysis after RKN infection. The results showed that three SlSUTs, 17 SlSWEETs, three SlTMTs, and SlVGT1 were upregulated in the leaves, whereas three SlSUTs, 17 SlSWEETs, two SlTMTs, and SlVGT1 were induced in the roots. To determine the function of the sugar transporters in the RKN infection process, we examined post-infection responses in the Atsuc2 mutant and pAtSUC2-GUS lines. β-glucuronidase expression was strongly induced at the infection sites, and RKN development was significantly arrested in the Atsuc2 mutant. Taken together, our analyses provide useful information for understanding the sugar transporter responses during early infection by RKNs in tomato.

Root-knot nematodes (RKNs) severely affect plants growth and productivity, and several commercial biocontrol bacteria can improve plants resistance to RKNs. Pseudomonas putida Sneb821 isolate was found to induce tomatoes resistance against Meloidogyne incognita. However, the molecular functions behind induced resistance remains unclear. Long non-coding RNA (lncRNA) is considered to be a new component that regulates the molecular functions of plant immunity. We found lncRNA was involved in Sneb821-induced tomato resistance to M. incognita. Compared with tomato inoculated with M. incognita, high-throughput sequencing showed that 43 lncRNAs were upregulated, while 35 lncRNAs were downregulated in tomatoes previously inoculated with Sneb821. A regulation network of lncRNAs was constructed, and the results indicated that 12 lncRNAs were found to act as sponges of their corresponding miRNAs. By using qRT-PCR and the overexpression vector pBI121, we found the expression of lncRNA44664 correlated with miR396/GRFs (growth-regulating factors) and lncRNA48734 was correlated with miR156/SPL (squamosal promoter-binding protein-like) transcription factors. These observations provided a novel molecular model in biocontrol bacteria-induced tomato resistance to M. incognita.

Soybean cyst nematode ( Heterodera glycines, soybean cyst nematode [SCN]) disease adversely affects the yield of soybean and leads to billions of dollars in losses every year. To control the disease, it is necessary to study the resistance genes of the plant and their mechanisms. Isoflavonoids are secondary metabolites of the phenylalanine pathway, and they are synthesized in soybean. They are essential in plant response to biotic and abiotic stresses. In this study, we reported that phenylalanine ammonia-lyase (PAL) genes GmPALs involved in isoflavonoid biosynthesis, can positively regulate soybean resistance to SCN. Our previous study demonstrated that the expression of GmPAL genes in the resistant cultivar Huipizhi (HPZ) heidou are strongly induced by SCN. PAL is the rate-limiting enzyme that catalyzes the first step of phenylpropanoid metabolism, and it responds to biotic or abiotic stresses. Here, we demonstrate that the resistance of soybeans against SCN is suppressed by PAL inhibitor l-α-(aminooxy)-β-phenylpropionic acid (L-AOPP) treatment. Overexpression of eight GmPAL genes caused diapause of nematodes in transgenic roots. In a petiole-feeding bioassay, we identified that two isoflavones, daidzein and genistein, could enhance resistance against SCN and suppress nematode development. This study thus reveals GmPAL-mediated resistance against SCN, information that has good application potential. The role of isoflavones in soybean resistance provides new information for the control of SCN. [ ] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Background: The yield of soybean is limited by the soybean cyst nematode (SCN, Heterodera glycines). Soybean transformation plays a key role in gene function research but the stable genetic transformation of soybean usually takes half a year. Methods: Here, we constructed a vector, pNI-GmUbi, in an Agrobacterium rhizogenes-mediated soybean hypocotyl transformation to induce fluorescent hairy roots (FHRs). Results: We describe the operation of FHR-SCN, a fast, efficient and visual operation pathosystem to study the gene functions in the soybean-SCN interaction. With this method, FHRs were detected after 25 days in 4 cultivars (Williams 82, Zhonghuang 13, Huipizhiheidou and Peking) and at least 66.67% of the composite plants could be used to inoculate SCNs. The demographics of the SCN could be started 12 days post-SCN inoculation. Further, GmHS1^pro-1 was overexpressed in the FHRs and GmHS1^pro-1 provided an additional resistance in Williams 82. In addition, we found that jasmonic acid and JA-Ile increased in the transgenic soybean, implying that the resistance was mainly caused by affecting the content of JA and JA-Ile. Conclusions: In this study, we established a pathosystem, FHR-SCN, to verify the functional genes in soybeans and the SCN interaction. We also verified that GmHS1^pro-1 provides additional resistance in both FHRs and transgenic soybeans, and the resistance may be caused by an increase in JA and JA-Ile contents.

SWEET (Sugars Will Eventually be Exported Transporter) proteins facilitate the movement of sugars through cell membranes and are essential for loading sucrose into phloem. Beyond its role in sugar transport, the SWEET protein also modulates plant resistance to various biotic and abiotic stresses. Among sugar transporter genes, GmSWEET20 is a positive regulatory factor involved in soybean cyst nematode ( Heterodera glycines) resistance. In this study, susceptible soybean cultivars (Williams 82) were used to conduct a transcriptome analysis to characterize the responses to nematode infection, in which multiple sugar transporter genes were highly expressed. The RT-qPCR analysis confirmed a significant increase in the expression of GmSWEET20 in soybean roots with H. glycines infection. Heterologous expression tests indicated that the protein encoded by GmSWEET20 does not transport hexose in yeast. Further analysis showed that soybean lines overexpressing GmSWEET20 exhibited increased resistance to H. glycines compared with the control. A yeast one-hybrid assay was employed to discover that LOC114390362 binds to the GmSWEET20 promoter. Transient expression in tobacco leaf cells revealed nucleus and cytosolic localization of LOC114390362. LOC114390362-overexpressing soybean lines showed a reduced number of nematode infections. Overall, the results indicate that the binding of LOC114390362 to the GmSWEET20 promoter plays a positive role in regulating soybean resistance to H. glycines. The GmSWEET20 gene has great potential to improve resistance to plant-parasitic nematodes in soybean and other plants.

Root-knot nematodes (Meloidogyne spp.) cause catastrophic yield losses in global agriculture. This study identified itaconic acid (IA), through comparative metabolomic analysis (the study of small molecules in biological systems), as a key virulence-related metabolite produced by the fungus Trichoderma citrinoviride Snef1910. In vitro assays demonstrated potent nematicidal activity of IA, with an LC ₅₀ value of 243.4 mg/liter against J2s of M. incognita and 78.4% egg-hatching inhibition at 800 mg/liter, performance that is comparable with the structural analog trans-aconitic acid. Pot and greenhouse field trials demonstrated that IA has a significant impact against M. incognita while enhancing tomato growth. Seed priming with IA compensated for the damage of nematodes to the photosynthetic pigments and activated systemic resistance of tomatoes, and treatment with 100 mg/liter of IA enhanced catalase and ascorbate peroxidase activities, while concurrently inhibiting H ₂ O ₂ /MDA accumulation. Crucially, IA production by T. citrinoviride positions this strain as a self-fertilizing organism for production of a nematicide with plant-growth-promoting properties. This study highlights the dual functionality of IA in nematode management, offering a sustainable alternative to synthetic agrochemicals.