野生型和ospk1突变体水稻幼苗根对外源糖分的吸收和响应

植物根系如何响应环境因子变化是植物发育和营养吸收研究的重要科学问题。丙酮酸激酶OsPK1在根部的表达主要在根尖成熟区和根毛区,其表达水平变化有可能影响水稻对外源糖分的吸收。采用日本晴和水稻突变体ospk1,通过改变1/2 MS培养基中蔗糖含量,探索水稻幼苗对外源糖分的吸收和响应。通过GC-MS的方法检测了水稻幼苗叶片、叶鞘和根中蔗糖、葡萄糖、果糖和半乳糖的含量。发现根与培养基中糖分接触能明显提高幼苗中的糖含量。并且这些幼苗的根系长度大于那些不加蔗糖的培养基培养的幼苗,表明外源糖分被吸收后能促进根的伸长。OsPK1表达下调影响了糖代谢和外源糖分的吸收。半定量RT-PCR结果显示,幼苗根与糖分的直接接触明显上调根中OsPIP2;4,OsPIP2;5和OsTIP2;1三个水孔蛋白基因的表达。

Uptake of exogenous sugars and responses by rice root of young wild-type and ospk1 mutant seedlings

How root system responds to various environmental factors has not yet been fully elucidated. In root, the expression of OsPK1 is mainly in the maturation zone and the root-hair zone of root tip. It is unknown whether the uptake of exogenous sugars by rice seedlings is affected by downregulation of OsPK1. In this study, we used wild-type (WT) and ospk1 rice mutant plants to investigate the uptake of exogenous sugars and the responses of rice seedlings by adding sucrose to 1/2 MS medium or not. The contents of sucrose, glucose, fructose and galactose in leaf blades, sheathes and roots of rice seedlings were measured by GC-MS analysis. The result revealed that direct contact between root and exogenous sugars greatly elevates sugar levels of rice seedlings. And the root length of these seedlings is much longer than that of the seedlings grown in medium omitting exogenous sugars, suggesting that uptake of exogenous sugars by root promotes root elongation. Downregulation of OsPK1 has effects on sugar metabolism and the uptake of exogenous sugars. Semi-quantitative RT-PCR result showed that the expressions of OsPIP2;4, OsPIP2;5 and OsTIP2;1 (three aquaporin genes) in root were greatly upregulated by the direct contact between root and exogenous sugars.