No abstract

Pod size of soybean is an important factor in the determination of seed weight. However, little is known about pod growth of soybean. Brassinosteroid, a group of phytohormones, regulate the pod growth of faba bean. We therefore investigated the role of brassinosteroid in pod growth of soybean. We measured pod length and cell number and cell area in pods treated with a brassinosteroid biosynthesis inhibitor. The inhibitor suppressed pod growth through the reduction of cell area. We then examined pod morphology and the expression of brassinosteroid biosynthesis (GmCYP450 85A1, 2 and 3) and response (GmBZR1, GmBES1 and GmBRU1) genes in the pods of two cultivars that differ in pod size. The difference in pod size was attributable to cell area, and the expression of brassinosteroid biosynthesis and response genes in pods was higher in the cultivar that has large pods. These results suggest that pod size of soybean is regulated through cell hypertrophy caused by brassinosteroid.

Seed desiccation during maturation is important for seed post-maturation behavior and harvest. However, the desiccation mechanism in soybean [Glycine max (L.) Merr.] seed maturation is hardly known. In this study, we found that water content in seeds, pods, and pedicels decreased faster than that in peduncles and stems. Therefore, we focused on the role of the pedicel during seed maturation. Morphological analysis revealed deposits in xylem vessels in the pedicel at 61 d after flowering (DAF), but no deposits in the peduncle. Microarray analysis showed that lignin biosynthesisrelated genes were expressed in the pedicel at 61 DAF. Among them, the expression of GmPAL, Gm4CL, GmC3H, and GmCAD increased in the pedicel during seed maturation. Pedicel lignin content also increased by 61 DAF; lignin accumulated in xylem vessels. These results suggest that lignin deposits in pedicel xylem vessels cause soybean seed desiccation during maturation. SUPPORTING INFORMATIONAdditional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Itoyama H, Nakagawa ACS, Ariyoshi Y, et al. Lignin deposits in pedicel xylem vessels regulate water transport during seed maturation in soybean. Crop Science.