Establishment of Agrobacterium-Mediated Transient Transformation System in Desert Legume Eremosparton songoricum (Litv.) Vass.

<i>Eremosparton songoricum</i> (Litv.) Vass. is a desert legume exhibiting extreme drought tolerance and the ability to withstand various harsh environments, making it a good candidate for investigating stress tolerance mechanisms and exploring valuable stress-resistant genes. However, the absence of a genetic transformation system for <i>E. songoricum</i> poses significant limitations for functionally validating these stress-resistant genes in situ. In this study, we developed an <i>Agrobacterium</i>-mediated transient transformation system for <i>E. songoricum</i> utilizing the β-glucuronidase (<i>GUS</i>) gene as a reporter. We investigated three types of explants (seedlings, assimilated branches and callus) and the effects of different <i>Agrobacterium</i> strains, seedling ages, OD₆₀₀ values, acetosyringone (AS) concentrations, sucrose concentrations and infection times on the transformation efficiency. The results reveal that the optimal transformation system was infecting one-month-old regenerating assimilated branches with the <i>Agrobacterium</i> strain C58C1. The infection solution comprised 1/2 MS medium with 3% sucrose and 200 μM AS at an OD₆₀₀ of 0.8, infection for 3 h and then followed by 2 days of dark cultivation, which achieving a maximum transformation rate of 97%. The maximum transformation rates of the seedlings and calluses were 57.17% and 39.51%, respectively. Moreover, we successfully utilized the assimilated branch transient transformation system to confirm the role of the previously reported transcription factor EsDREB2B in <i>E. songoricum</i>. The overexpression of <i>EsDREB2B</i> enhanced drought tolerance by increasing the plant's reactive oxygen species (ROS) scavenging capacity in situ. This study established the first transient transformation system for a desert legume woody plant, <i>E. songoricum</i>. This efficient system can be readily applied to investigate gene functions in <i>E. songoricum</i>. It will expedite the exploration of genetic resources and stress tolerance mechanisms in this species, offering valuable insights and serving as a reference for the transformation of other desert plants and woody legumes.