Quantitative Change Of Endogenous Brassinosteroids And Their Synthesis/Metabolism Gene Transcripts During Maturation And Germination Of Pea Seeds

Abstract

During the rapid growth of pea seeds, the levels of brassinolide (BL) and castasterone (CS) as well as the expression of the D gene that catalyses the conversion of 6-deoxoCS to CS, were increased. When the seed growth ceased, the D expression, as well as the levels of BL and CS, was decreased, but the level of 6-deoxoCS was accumulated. Thus the D enzyme seems to be responsible for the synthesis of CS and hence BL in seeds. The metabolic enzyme BAS1 was continuously expressed throughout the seed growth with little fluctuation. A large decrease of 6-deoxoCS and disappearance of CS and BL in mature seeds may be ascribed to the action of the BAS1 enzyme. The levels of upstream precursors were not decreased greatly, indicating that these precursors may be storage forms. Analysis of the levels of BRs and BR biosynthesis/catabolism gene transcripts during seed germination is in progress.