Optimization of preparation and transformation of protoplasts from Populus simonii × P. nigra leaves and subcellular localization of the major latex protein 328 (MLP328)

Abstract

Background Populus simonii × P. nigra is an ideal material for studying the molecular mechanisms of woody plants. In recent years, research on Populus simonii × P. nigra has increasingly focused on the application of transgenic technology to improve salt tolerance. However, the rapid characterization of gene functions has been hampered by the long growth cycle and exceedingly poor transformation efficiency. Protoplasts are an important tool for plant gene engineering, which can assist with challenging genetic transformation and the protracted growth cycle of Populus simonii × P. nigra. This study established an optimized system for the preparation and transformation of protoplasts from Populus simonii × P. nigra leaves, making genetic research on Populus simonii × P. nigra faster and more convenient. Major Latex Protein (MLP) family genes play a crucial role in plant salt stress response. In the previous study, we discovered that PsnMLP328 can be induced by salt treatment, which suggested that this gene may be involved in response to salt stress. Protein localization is a suggestion for its function. Therefore, we conducted subcellular localization analysis using protoplasts of Populus simonii × P. nigra to study the function of the PsnMLP328 gene preliminarily. Results This study established an optimized system for the preparation and transformation of Populus simonii × P. nigra protoplasts. The research results indicate that the optimal separation scheme for the protoplasts of Populus simonii × P. nigra leaves included 2.5% cellulase R-10, 0.6% macerozyme R-10, 0.3% pectolyase Y-23, and 0.8 M mannitol. After enzymatic digestion for 5 h, the yield of obtained protoplasts could reach up to 2 × 107 protoplasts/gFW, with a high viability of 98%. We carried out the subcellular localization analysis based on the optimized transient transformation system, and the results indicated that the MLP328 protein is localized in the nucleus and cytoplasm; thereby proving the effectiveness of the transformation system. Conclusion In summary, this study successfully established an efficient system for preparing and transforming leaf protoplasts of Populus simonii × P. nigra, laying the foundation for future research on gene function and expression of Populus simonii × P. nigra.