NRT1.1/ NPF6.3和钼酸根转运蛋白MOT1调控草莓植株NO3–吸收利用的作用机制

It’s urgent to solve the problem how to use nitrogen fertilizer rationally. Nitrate (NO3–) is the main nitrogen source of strawberry. The excessive application of nitrogen fertilizer not only increases the cost of planting, but also reduces the utilization of nitrogen fertilizer and pollutes the environment. So it is important for studying the genes to reduce fertilizer use and improve quality. NRT1.1/NPF6.3 is demonstrated to act as a transceptor (transporter and receptor) for NO3– and it can transport and sense NO3–. Molybdate transporter MOT1 can be involved into the assimilation and distribution process of MoO42- and participates in the NO3–assimilation process. In our preliminary studies, strawberries showed symptoms of nitrogen deficiency in the Mo deficiency condition, and MoO42- can regulate the expression of NRT1.1 and MoO42- induces the expression of MOT1. It is speculated that NRT1.1 and MOT1 may jointly regulate the absorption and utilization of NO3–. Therefore, we will study the interaction between the absorption and utilization of MoO42- and NO3– using the split-root system and isotopic labeling (99MoO42- and 15NO3–). We have cloned FaNRT1.1 and FaMOT1and will confirm the regulation of the absorption and utilization of NO3– through physiological and biochemical analysis and transgenic research, which will provide new molecular and physiology basis for improving the nitrogen utilization of strawberries.

合理利用氮肥是减肥增效中亟待解决的问题。硝态氮（NO3–）是草莓最主要的氮源，而氮肥的大量施用不仅增加了种植成本，而且降低了氮肥利用率。因此，研究提高NO3–利用的基因是减肥增效的关键科学问题。研究表明AtNRT1.1/NPF6.3能转运和感知NO3–，钼酸盐转运蛋白MOT1可以吸收分配钼酸根（MoO42-），参与NO3–的同化利用途径。申请人前期研究发现缺Mo条件下草莓表现出氮缺乏症状，MoO42-调控NRT1.1的表达，NO3–则诱导了MOT1的表达，推测NRT1.1和MOT1可能共同调控NO3–的吸收利用。为此，我们利用分根系统和同位素标记(99MoO42-和15NO3–)研究MoO42-和NO3–的吸收利用的相互影响，克隆了草莓中的FaNRT1.1和FaMOT1基因，通过生理生化分析和转基因手段进一步研究两者对NO3-的吸收利用的调控，为提高草莓的氮素利用率提供新的分子生理依据。

硝态氮（NO3–）是草莓最主要的氮源，而氮肥的大量施用增加种植成本，降低氮肥利用率。钼（Mo）是植物生长发育所必需的一种微量元素，参与到植物的氮代谢中。NRT1.1作为NO3–的‘收发器’能转运和感知NO3–，钼酸盐转运蛋白MOT1可以吸收分配MoO42-，参与NO3–的同化利用过程。然而NRT1.1和MOT1如何共同调控NO3–的吸收利用尚不清楚。本研究利用分根系统和同位素标记(99MoO42-和15NO3–)发现，NO3-显著提高草莓99MoO42-吸收量。MoO42-显著提高草莓15NO3-含量。利用GUS染色研究发现Mo能够增强NRT1.1活性，NO3-能够增强MOT1活性。本硏究获得了草莓沉默植株（FvMOT1RNAi和FvNRT1.1RNAi）和拟南芥过表达植株（35S:FvMOT1和35S:FvNRT1.1）。NO3-能够诱导35S:FvMOT1植株MOT1的表达，使得Mo浓度显著升高。FvMOT1RNAi植株NRT1.1的表达下降，15NO3–吸收速率和15NO3–含量降低，使得15NO3–的利用率降低，35S:FvMOT1植株表现出相反的趋势。表明MOT1通过对MoO42-吸收转运来实现对NO3–利用的调控，从而负反馈调节NRT1.1对NO3-的吸收。沉默掉NRT1.1后，植株的MOT1表达水平下降，使得Mo浓度也降低。35S:FvNRT1.1植株的MOT1表达水平和Mo浓度得以提高。和FvNRT1.1RNAi植株相比，35S:FvNRT1.1植株15NO3–吸收速率显著提升，15NO3–含量增多，15NO3–的利用率显著提高。表明NRT1.1通过调控 MOT1的吸收转运活性来实现对MoO42-吸收的调控，从而调控NO3–的同化利用。以上研究为利用基因工程选育草莓氮素利用新品种提供新的分子生理依据。

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