星星草(Puccinellia tenuifolra)铵转运蛋白(PutAMT)及N、C末端缺失对NH_4^+吸收能力的影响

Effect of Ammonium Transporter (PutAMT) and N-、C-terminally Truncated Forms on NH_4^+ Uptake Capacity in Puccinellia tenuifolra

铵是植物吸收利用的主要氮源之一,NH4+的吸收主要通过铵转运蛋白(AMT)进行运输。本研究克隆了星星草铵转运蛋白(PutAMT),以GFP为标记构建了植物表达载体,观察表明PutAMT蛋白明显定位于质膜,但是根据观察发现PutAMT蛋白的定位具有复杂性及多样性的特点。为了深入了解铵转运蛋白的结构对NH4+吸收能力的影响,构建了N、C及NC末端缺失的PutAMT(ΔNPutAMT,ΔCPutAMT及ΔNCPutAMT)的载体,转入酵母突变体菌株31019b进行NH4+吸收能力的实验,结果显示了全长PutAMT在低氮条件下具有较强的吸收NH4+的功能。N、C及NC末端缺失的突变体与全长PutAMT相比,对NH4+的吸收能力有下降的趋势。结果表明了,N、C末端对NH4+的吸收起到重要的作用。

Ammonium is one of the important inorganic nitrogen source in plant absorption and utilization; the absorption of NH4＋ is mainly transported by the ammonium transporter （AMT）. In this study, we cloned ammonium transporter （PutAMT） from Puccinellia tenuifolra. By means of the plant expression vector constructed with GFP marker, the observing results indicated that the PutAMT protein was mainly localized on the plasma membrane, however, according to the further observation we found the characteristics of PutAMT localization presented complexity and diversity. To further study how did the structure of ammonium transporter influence on the uptake capacity of NH4＋, three truncated forms of PutAMT were constructed （ΔNPutAMT, ΔCPutAMT and ΔNCPutAMT）, and the constructed vectors were introduced into yeast mutant strain 31019b. The results showed that the full-length of PutAMT had the function of NH4＋ uptake under the condition of the low NH4＋ concentration, while three truncated forms of PutAMT （ΔNPutAMT, ΔCPutAMT and ΔNCPutAMT） led to lost the capacity of NH4＋ uptake. The results suggested that N- or C-terminal should be both important for NH4＋ uptake.