Establishment of an efficient virus-induced gene silencing (VIGS) assay in Arabidopsis by Agrobacterium-mediated rubbing infection

Developing and applying a virus-induced gene silencing system for functional genomics in walnut (Juglans regia L.) mediated by tobacco rattle virus

Walnut (Juglans regia L.) is a high-value tree species planted worldwide, but the incomplete less developed genetic transformation system limits its gene function analysis. In this study, virus-induced gene silencing (VIGS) mediated by tobacco rattle virus (TRV) technology was applied to walnut seedlings to degrade the transcript of target gene. Different infiltration methods were used to explore the effects of infection mode, Agrobacterium cell density, silencing fragment length, and walnut cultivars. The results showed that spray infiltration of seedlings resulted in a photobleaching phenotype of the whole plant. Leaf injection was a more effective way of infiltration. The optimal combination was the Agrobacterium cell density at OD600 = 1.1 with target fragment = 255 bp for the treatment of walnut early-fruiting cultivar 'Xiangling.' This combination can reach up to 48 % of gene silencing efficiency. Based on this optimized VIGS system, silencing a walnut chlorophyll synthesis-related gene, JrPOR (Protochlorophyllide reductase), to further validate the system's effect. The results showed that the expression of JrPOR was significantly repressed, and the chlorophyll level of the silenced plants was significantly decreased compared with the control. The above results indicate that the walnut TRV-VIGS system has been successfully established and can be used for reverse genetic studies, providing an option for verifying gene function in walnut.

HrTPS12 gene dramatically enhanced insect resistance of sea buckthorn to infection by fruit fly (Rhagoletis batava obseuriosa Kol.)

BACKGROUND

Terpenoids emitted from plants are important for regulating plant-insect interaction. However, it is still unclear how terpenoids affect the host defense system. There are few reports of terpenoids' involvement in the mechanisms that regulate woody plants' insect resistance.

RESULTS

The (E)-β-ocimene of terpenes was only found in RBO-resist leaves, and its content was higher than that of other type terpenes. Further, we also found (E)-β-ocimene had a significant avoidance effect on RBO and reached 87.5% of the highest avoidance rate. Meanwhile, overexpression of HrTPS12 in Arabidopsis increased the HrTPS12 expression level, (E)-β-ocimene content, and enhanced the defense against RBO. However, silencing HrTPS12 in sea buckthorn revealed that the expression levels of HrTPS12 and (E)-β-ocimene significantly decreased, causing the attraction effect on RBO.

CONCLUSION

HrTPS12 was an up-regulator, which improves sea buckthorn resistance to RBO by regulating the synthesis of volatile (E)-β-ocimene. These results provide in-depth information about the interaction between RBO and sea buckthorn and provide a theoretical basis for developing plant-based insect repellents that can be used to manage RBO. © 2023 Society of Chemical Industry.

Screening and Verification of Photosynthesis and Chloroplast-Related Genes in Mulberry by Comparative RNA-Seq and Virus-Induced Gene Silencing

Photosynthesis is one of the most important factors in mulberry growth and production. To study the photosynthetic regulatory network of mulberry we sequenced the transcriptomes of two high-yielding (E1 and E2) and one low-yielding (H32) mulberry genotypes at two-time points (10:00 and 12:00). Re-annotation of the mulberry genome based on the transcriptome sequencing data identified 22,664 high-quality protein-coding genes with a BUSCO-assessed completeness of 93.4%. A total of 6587 differentially expressed genes (DEGs) were obtained in the transcriptome analysis. Functional annotation and enrichment revealed 142 out of 6587 genes involved in the photosynthetic pathway and chloroplast development. Moreover, 3 out of 142 genes were further examined using the VIGS technique; the leaves of MaCLA1- and MaTHIC-silenced plants were markedly yellowed or even white, and the leaves of MaPKP2-silenced plants showed a wrinkled appearance. The expression levels of the ensiled plants were reduced, and the levels of chlorophyll b and total chlorophyll were lower than those of the control plants. Co-expression analysis showed that MaCLA1 was co-expressed with CHUP1 and YSL3; MaTHIC was co-expressed with MaHSP70, MaFLN1, and MaEMB2794; MaPKP2 was mainly co-expressed with GH9B7, GH3.1, and EDA9. Protein interaction network prediction revealed that MaCLA1 was associated with RPE, TRA2, GPS1, and DXR proteins; MaTHIC was associated with TH1, PUR5, BIO2, and THI1; MaPKP2 was associated with ENOC, LOS2, and PGI1. This study offers a useful resource for further investigation of the molecular mechanisms involved in mulberry photosynthesis and preliminary insight into the regulatory network of photosynthesis.

Efficient virus-induced gene silencing in Hibiscus hamabo Sieb. et Zucc. using tobacco rattle virus

Background

Hibiscus hamabo Sieb. et Zucc. is a semi-mangrove plant used for the ecological restoration of saline-alkali land, coastal afforestation and urban landscaping. The genetic transformation H. hamabo is currently inefficient and laborious, restricting gene functional studies on this species. In plants, virus-induced gene silencing provides a pathway to rapidly and effectively create targeted gene knockouts for gene functional studies.

Methods

In this study, we tested the efficiency of a tobacco rattle virus vector in silencing the cloroplastos alterados 1 (CLA1) gene through agroinfiltration.

Results

The leaves of H. hamabo showed white streaks typical of CLA1 gene silencing three weeks after agroinfiltration. In agroinfiltrated H. hamabo plants, the CLA1 expression levels in leaves with white streaks were all significantly lower than those in leaves from mock-infected and control plants.

Conclusions

The system presented here can efficiently silence genes in H. hamabo and may be a powerful tool for large-scale reverse-genetic analyses of gene functions in H. hamabo.