水通道蛋白（AQP）影响水稻叶片光合氮素利用效率的机制研究

the previous results demonstrated that the chloroplast volume of rice leaf became larger, mesophyll conductance and Rubisco activity did not increase respondingly under high nitrogen supplied, all of those which caused the reduce of PNUE.On the basis of that,the target of this study is to clarify that the mechanism of how aquaporin affect rice leaf PNUE.The methods of nutrient solution culture and different expression origin systems would be used to (1)study the differance of rice leaf photosynthesis efficiency between different rice cultivars,discussing the effects of AQP on the efficiency;(2)analyse the effects of different nitrogen efficiency rice cultivars leaf nitrogen content,forms and distribution on AQP,elucidating the effect of the change of AQP expression and activity on photosynthesis;(3)constitute the relationships between AQP and chloroplast development and further study how AQP affect photosynthesis.The development of chloroplast could be controled by the control of AQP expression and activity.However,we could increase the efficiency of photosynthesis and lastly,enhance PNUE.The results of the study could not only give a new methods to enhance PNUE but also clarify the relationship between nitrogen nutrition and photosynthesis,mostly could increase nitrogen use efficiency and guarantee the sustaining development of agriculture.

前期研究结果表明，高氮条件下叶绿体体积变大，叶肉导度与Rubisco活性未同步增加是PNUE降低的主要原因，本项目在此基础上拟阐明水通道蛋白（AQP）影响水稻叶片光合氮素利用效率的机制。采用室内营养液培养，结合利用异源表达系统，研究：（1）不同氮素效率品种水稻的光合效率差异，探讨不同水稻品种叶片AQP活性及其在影响光合效率中的作用；（2）分析不同品种水稻（氮高效与氮低效）叶片氮素含量、形态及分布对AQP的影响，阐明AQP表达和活性的改变对光合效率的影响机制；（3）建立AQP与叶绿体发育之间的关系，进一步研究AQP对光合作用的影响，通过对叶片AQP表达或者活性的调控，提高叶片的光合效率，最终提高PNUE。项目研究成果不仅为研究提高光合氮素利用率提供新的思路，也有助于揭示水稻氮素营养与光合作用的本质，更可以从根本上提高氮素利用率，为农业可持续发展提供保障。

为研究水通道蛋白(AQP)调控水稻光合氮素利用率的生理机制，采用室内营养液培养，研究了不同氮素供应对水稻AQP表达、水分吸收及叶片光合氮素利用率的影响。结果表明，（1）高氮条件下水稻叶片CO2总导度降低，叶绿体内实际CO2浓度显著低于理论值，最终导致光合氮素利用率显著降低；（2）高氮条件下叶片AQP表达量降低是导致CO2总导度降低的主要原因，AQP表达量与单位氮素CO2总导度间存在显著正相关关系；（3）ospip1;1突变体的气孔导度及叶肉导度显著低于野生型水稻，从而导致其叶片光合速率和生物量显著降低，说明PIP1;1在CO2传输中发挥重要作用；（4）随供氮量的增加，水稻根系AQP基因表达量显著增加，通气组织形成减少，根系孔隙度降低，水流导度增加；（5）水分胁迫导致水稻生物量显著降低，硝营养水稻更明显，水分胁迫后铵态氮植株根系AQP表达量及水流导度的增加是导致其抗旱性增强的主要原因；（6）水分胁迫4小时后水稻根系AQP表达量降低，24小时后植株ABA含量及根系AQP表达量在铵态氮条件下显著升高，说明AQP对铵态氮水稻抗旱性的调控与ABA含量有关。