Role of seed specific trehalose synthesis pathway, OsTPS9-OsTPP3, in the regulation of rice grain development

Rice grain development is a key stage in the formation of rice yield and quality. More and more studies have shown that trehalose synthesis pathway plays a key role in grain development. However, earlier studies either used heterologous expression technology, or focused on the role of trehalose synthesis genes on the leaf assimilate transportation to the grains, resulting in different or even contrary conclusions about its role on grain development. Different crops may have different stories. How exactly the trehalose synthesis pathway works during rice grain development remains unclear.

Trehalose (Tre) is a non-reducing disaccharide sugar composed of two glucose units. Its precursor trehalose-6-phosphate (T6P) is first synthesized from UDP-glucose and glucose-6-P by trehalose-6-phosphate synthase (TPS) and then converted to Tre by trehalose-6-phosphate phosphatase (TPP). Our previous studies showed that OsTPP3 gene was involved in regulating grain filling of rice inferior spikelets in response to post-anthesis moderate soil drying. Further analysis showed that both OsTPS9 and OsTPP3 were specifically expressed in grain during early development stage. Overexpression of OsTPS9 or knockout of OsTPP3 led to increased grain length and decreased grain thickness, while overexpression of OsTPP3 reduced grain length, grain width and grain thickness, suggesting that the trehalose synthesis pathway, OsTPS9- OsTPP3, which is specifically expressed in rice grain, may be involved in regulating grain development.

Based on these earlier works, we shall first identify the upstream regulatory factors of OsTPS9 and OsTPP3 pathway by using physiological and molecular techniques to reveal the molecular regulatory mechanisms during grain development. Then detailed physiological and molecular mechanisms showing how OsTPS9-OsTPP3 pathway works during the grain development will be studied. The outcomes of this project will yield new genetic resources for the genetic improvement of rice in terms of yield and quality and crucial information about how these key genes coordinate in rice.