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内容記述 |
Yield is one of the most important crop traits. Most of the previous studies on yield have mainly focused on source and/or sink organs such as leaf, seed and fruit. Although the stem plays a role as a pathway of long-distance transport between source and sink organs, few studies have focused on the stem. Our previous work suggests that the stem does not only functions as a transport conduit but also plays a role in regulating the partitioning of the photoassimilates. In a previous study, we generated starch-deficient lines and confirmed modified sink strength in the fruits in tomato. Since photoassimilates partitioning is expected to be influenced in those lines, in this study we analyzed assimilate transport profile in the stem of wild-type (WT) and the starch-deficient line by the Positron-Emitting Tracer Imaging System (PETIS). Comparison of translocation profile between WT and the starch-deficient line showed that faster photoassimilates transport in the starch-deficient line than in WT. In addition, while the photoassimilates were mainly transported towards the fruit bunch in the WT, it tended to pass through the basal node of the bunch and flow towards to the base in the starch-deficient lines. These results indicate that flow of the photoassimilates transport were altered at the basal node of fruit bunch in the starch-defect line. To analyze the comprehensive gene expression in these lines, we performed RNA-/miRNA-seq analyses with the stem tissues such node, internode and peduncle. The PCA analyses revealed that the gene expression profiles of the starch-deficient line were remarkably altered in the node and internode compared to WT whereas no significant change was observed in the peduncle tissue. In these tissues, not only sugar transporter genes but also organic acid and sugar phosphate metabolic enzyme genes showed differential expression patterns in the node and/or internode tissues, suggesting that these metabolic dynamics may affect the altered assimilate transport in the starch-deficient lines. Notably, several miRNAs associated with sugar signaling showed stem tissue-specific expression patterns. Functional analysis of these genes and miRNAs will facilitate our understanding on the mechanisms underlying photoassimilates partitioning at the basal node of the fruit bunch. |
