Lignin deposits in xylem vessels of pedicel regulate water transport during seed maturation in soybean (Glycine max L. Merr.)

Seed desiccation during maturation is important process for seed post-maturation behavior and harvest. However, the desiccation mechanism in soybean seed maturation is hardly known. In this study, water content in seed, pod and pedicel decreased faster than that in peduncle and stem. Therefore, we focus on the pedicel during seed maturation. By morphological analysis, the deposits in xylem vessels were confirmed in pedicel at 61 day after flowering (DAF), when there are not the deposits in peduncle. It was clarified by microarray analysis that lignin biosynthesis related genes expressed in pedicel at 61 DAF. Indeed, GmPAL, Gm4CL, GmC3H and GmCAD, which are lignin biosynthesis related genes, increased in pedicel during seed maturation. Furthermore, lignin content in pedicel also increased toward at 61 DAF and accumulated in the xylem vessels. These results suggested that lignin deposits into xylem vessels in pedicel cause the soybean seed desiccation during seed maturation. Differentially expressed genes between the pedicels at 51 and 66 days after flowering in soybean.