A Transporter at the Node Responsible for Intervascular Transfer of Silicon in Rice

Abstract

The concentration of essential mineral nutrients in the edible portion of plants such as grains may affect the nutritional value of these foods, while concentrations of toxic minerals in the plant are matter of food safety. Minerals taken up by the roots from soils are normally redirected at plant nodes before they are finally transported into developing seeds. However, the molecular mechanisms involved in this process have not been identified so far. Herein, we report on a transporter (Lsi6) responsible for the redirection of a plant nutrient at the node. Lsi6 is a silicon transporter in rice (Oryza sativa), and its expression in node I below the panicles is greatly enhanced when the panicle is completely emerged. Lsi6 is mainly localized at the xylem transfer cells located at the outer boundary region of the enlarged large vascular bundles in node I. Knockout of Lsi6 decreased Si accumulation in the panicles but increased Si accumulation in the flag leaf. These results suggest that Lsi6 is a transporter involved in intervascular transfer (i.e., transfer of silicon from the large vascular bundles coming from the roots to the diffuse vascular bundles connected to the panicles). These findings will be useful for selectively enhancing the accumulation of essential nutrients and reducing toxic minerals in the edible portion of cereals.

Orchestration of three transporters and distinct vascular structures in node for intervascular transfer of silicon in rice

“…These samples were also used for analysis of Lsi6 previously (14). Similar to Lsi6, the highest expression of both Lsi2 and Lsi3 was found in the uppermost node I ( Fig.…”

“…Lsi6 in nodes is polarly localized at the xylem parenchyma cells (mainly XTCs) of EVBs (14). Knockout of Lsi6 resulted in decreased Si accumulation in the husk but increased Si in the flag leaf (14). However, Lsi6 is a channel-type passive transporter, which transports silicic acid following concentration gradient (13,15).…”

“…Lsi6 in nodes is polarly localized at the xylem parenchyma cells (mainly XTCs) of EVBs (14). Knockout of Lsi6 resulted in decreased Si accumulation in the husk but increased Si in the flag leaf (14).…”

Relationships between Biomass Composition and Liquid Products Formed via Pyrolysis

“…Advances in understanding cell wall biosynthesis, including genes responsible for synthesizing the major polymer classes (Bonawitz and Chapple, 2010;Scheller and Ulvskov, 2010;Pauly et al, 2013) and covalent interactions among them (Chiniquy et al, 2012;Bartley et al, 2013;Schultink et al, 2015); regulation of expression of the cell wall biosynthesis genes (Zhao and Dixon, 2011); and metal ion transport proteins that determine the abundance and distribution of plant mineral content (Ma et al, 2006;Yamaji and Ma, 2009;Zhong and Ye, 2015), lay the foundation for genetically engineering bioenergy crop cell wall content and structure. For example, lignin is an important target for genetic engineering for pyrolysis since the major lignin-derived products have a lower O:C ratio, a higher energy value, and are more stable than sugar-derived products (Tanger et al, 2013;Mante et al, 2014).…”

A family of diatom-like silicon transporters in the siliceous loricate choanoflagellates

“…SIT-like genes have been found in other siliceous stramenopiles (Synura and Ochromonas [8]), but in no other groups. Land plants do not possess SIT-like genes, instead possessing NOD26-like intrinsic protein (NIP)-type transporters for silicic acid (Lsi1, Lsi6) [9,10] and active silicon efflux pumps (Lsi2) [11]. No SITs are known from siliceous sponges, but a Na þ =HCO À 3 co-transporter has been postulated to have a role in silicon transport [12].…”