期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：36
页码：11401-11406
DOI：10.1073/pnas.1508987112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceRequirement of mineral elements differs with different organs and tissues; therefore, plants have developed systems for preferentially delivering mineral elements to tissues with high requirement. However, the molecular mechanisms for these systems are poorly understood. We took silicon (Si) as an example and revealed an efficient distribution system occurring in the node of rice, which is a hub for distribution. We found that hyperaccumulation of Si in the husk (more than 10%) is achieved by cooperation of three different Si transporters localized at the different cell layers in the node. Furthermore, mathematical modeling showed that an apoplastic barrier and development of enlarged vascular bundles are also required. Our work revealed a set of players for efficient distribution control in node. Requirement of mineral elements in different plant tissues is not often consistent with their transpiration rate; therefore, plants have developed systems for preferential distribution of mineral elements to the developing tissues with low transpiration. Here we took silicon (Si) as an example and revealed an efficient system for preferential distribution of Si in the node of rice (Oryza sativa). Rice is able to accumulate more than 10% Si of the dry weight in the husk, which is required for protecting the grains from water loss and pathogen infection. However, it has been unknown for a long time how this hyperaccumulation is achieved. We found that three transporters (Lsi2, Lsi3, and Lsi6) located at the node are involved in the intervascular transfer, which is required for the preferential distribution of Si. Lsi2 was polarly localized to the bundle sheath cell layer around the enlarged vascular bundles, which is next to the xylem transfer cell layer where Lsi6 is localized. Lsi3 was located in the parenchyma tissues between enlarged vascular bundles and diffuse vascular bundles. Similar to Lsi6, knockout of Lsi2 and Lsi3 also resulted in decreased distribution of Si to the panicles but increased Si to the flag leaf. Furthermore, we constructed a mathematical model for Si distribution and revealed that in addition to cooperation of three transporters, an apoplastic barrier localized at the bundle sheath cells and development of the enlarged vascular bundles in node are also required for the hyperaccumulation of Si in rice husk.
关键词：node ; rice transporter ; apoplastic barrier ; silicon distribution ; mathematical model
