MALDI Matrix Deposition for Litchi Seed Tissue

After being air-dried, the serial litchi seed tissue sections were used for MALDI matrix coating (Figure 1C). A 2-MBT matrix solution was prepared at an optimal concentration of 15 mg/ml and dissolved in methanol/water/TFA (80:20:0.2, v/v/v). Air-dried tissue sections were coated with the 2-MBT matrix solution by a GET-Sprayer (III) (HIT Co., Ltd, Beijing, China). Briefly, the 2-MBT matrix solution 15 cycles (5 s spray, 10 s incubation, and 20 s drying time) was sprayed on the surface of the tissue sections to pre-seed a thin layer of the 2-MBT matrix. After the tissue sections were completely air-dried in a vented fume hood, the matrix solution was evenly sprayed for 50 more of the same cycles.