Influence of repressed expression of OsBAM5, one of beta-amylase genes, on the growth and the starch content in rice seedlings
2016
Sugimura, Y. (Meijo University, Nagoya (Japan). Graduate School of Agricultural Science, Laboratory of Crop Science) | Hirano, M. | Michiyama, H. | Hirano, T.
In leaves of higher plants, starch is transiently stored in the chloroplasts during the day, and subsequently degraded during the night to supply sugars required for their growth. Thus, it is important to elucidate the processes of starch degradation in leaves in order to understand the relationships between the metabolism of photoassimilates and the growth. The purpose of this study is to clarify the involvement of OsBAM5, one of beta-amylase genes, in starch degradation of 16-day-old seedlings. The control plants to which empty-vector was introduced had low level of the starch content at 6:00 within a day. However, the content increased from 12:00 to 18:00 and remained at a high level from 18:00 to 24:00. These results indicate that starch transiently accumulated in the leaves was degraded from 24:00 to 6:00 and utilized for their growth. In control plants, OsBAM5 was expressed at a low level at 12:00, but its mRNA level markedly increased at 24:00 and 6:00. In addition, the knockdown plants of OsBAM5 (BAM5 KD) exhibited starch-excess phenotype in the leaves. These results indicate that OsBAM5 may play an important role in starch degradation in rice seedlings. The length of seedlings was significantly lower in BAM5 KD than control plants. Therefore, the excess accumulation of starch induced by the repressed expression of OsBAM5 may lead to delay of the plant growth.
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