Within-population variation in susceptibility to Agrobacterium tumefaciens A281 in Picea abies (L.) Karst

Refinement and Enhancement of Agrobacterium-Mediated Transient Transformation for Functional Gene Examination in Mulberry (Morus L.)

Background: Mulberry (Morus L.), a vital perennial woody plant with significant economic importance, is utilized for silkworm rearing, human consumption and medicinal use. The availability of mulberry's whole-genome sequencing data has underscored the demand for an effective, user-friendly, and high-throughput protocol to facilitate the elucidation of gene functions. Methods and Results: In this investigation, we established a transient transformation approach using Agrobacterium tumefaciens-mediated sonication followed by vacuum infiltration in mulberry tissue culture seedlings. Simultaneously, we optimized the transformation conditions, including mulberry genotypes, A. tumefaciens strain, acetosyringone concentration, bacterial density, sonication time, and days after agroinfiltration. These optimizations aimed to achieve heightened transformation efficiency, employing GFP as a reporter gene to monitor transformation events. The optimized method included the use of an infiltration medium (10 mM MgCl2, 10 mM MES (2-(N-morpholino)ethanesulfonic acid sodium salt), 150 μM acetosyringone, and OD600 0.5 of A. tumefaciens LBA4404) supplemented with the surfactant 0.02% Silwet L-77, with 20 s sonication followed by 20 min vacuum infiltration (0.07 MPa). Among the four mulberry genotypes, 'Taiguo' was the most responsive genotype and produced the highest levels of GFP expression at 7 d after infiltration. Furthermore, the optimized transient transformation approach has been proven to be successfully applicable for transiently overexpressing MaANS and MaDFR in mulberry fruits of 'Taiguo', in vitro, which distinctly enhanced fruit coloring and significantly increased anthocyanin accumulation, respectively. Conclusions: In summary, we devised a dependable, stable and highly efficient transient transformation approach suitable for rapid gene function examination in mulberry leaves and fruits, in vitro.

Development and optimization of agroinfiltration for soybean

KEY MESSAGE

Agroinfiltration is an efficient method to study transgene expression in plant tissue. In this study, sonication followed by vacuum infiltration is shown to increase agroinfiltration-mediated GUS expression in soybean. Agroinfiltration, a valuable tool for rapid analysis of gene function, has been used extensively on leaf tissue of Nicotiana benthamiana and several other plant species. However, the application of this approach for gene functionality studies in soybean has been largely unsuccessful. Improvements in agroinfiltration of many plants have been achieved through a variety of approaches to allow better delivery, penetration and infection of Agrobacterium to interior leaf tissues. In this work, an agroinfiltration approach was developed for transient expression in soybean utilizing sonication followed by vacuum infiltration of intact seedlings. The optimal infiltration buffer, sonication time, and vacuum conditions for agroinfiltration of soybean were evaluated by monitoring expression of an introduced β-glucuronidase (GUS) reporter gene. The developed method included the use of an infiltration buffer (10 mM 2-(N-morpholino)ethanesulfonic acid sodium salt, 10 mM MgCl2, 100 µM acetosyringone) supplemented with the reducing agent dithiothreitol, with 30 s sonication followed by vacuum infiltration. These techniques were further applied to evaluate five different Agrobacterium strains and six different plant genetic backgrounds. Among the Agrobacterium strains examined, J2 produced the highest levels of GUS activity and 'Peking' was the most responsive genotype.