Ammonium (NH4+) and nitrate (NO3?) are major inorganic nitrogen (N) sources for plants. When serving as the sole or dominant N supply, NH4+often causes root inhibition and shoot chlorosis in plants, known as ammonium toxicity. NO3?usually causes no toxicity and can mitigate ammonium toxicity even at low concentrations, referred to as nitrate-dependent alleviation of ammonium tox-icity. Our previous studies indicated a NO3?efflux channel SLAH3 is involved in this process. How-ever, whether additional components contribute to NO3?-mediated NH4+detoxification is unknown. Previously, mutations in NO3?transporter NRT1.1 were shown to cause enhanced resistance to high concentrations of NH4+. Whereas, in this study, we found when the high-NH4+ medium was sup-plemented with low concentrations of NO3?, nrt1.1 mutant plants showed hyper-sensitive phenotype instead. Furthermore, mutation in NRT1.1 caused enhanced medium acidification under high-NH4+/low-NO3?condition, suggesting NRT1.1 regulates ammonium toxicity by facilitating H+ uptake. Moreover, NRT1.1 was shown to interact with SLAH3 to form a transporter-channel complex. Interestingly, SLAH3 appeared to affect NO3?influx while NRT1.1 influenced NO3? efflux, sug-gesting NRT1.1 and SLAH3 regulate each other at protein and/or gene expression levels. Our study thus revealed NRT1.1 and SLAH3 form a func-tional unit to regulate nitrate-dependent alleviation of ammonium toxicity through regulating NO3?transport and balancing rhizosphere acidification.

Chengbin Xiao;Doudou Sun;Beibei Liu;Xianming Fang;Pengcheng Li;Yao Jiang;Mingming He;Jia Li;Sheng Luan;Kai He

Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations,School of Life Sciences,Lanzhou University,Lanzhou 730000,China;School of Life Sciences,Henan Agricultural University,Zhengzhou 450000,China;School of Life Sciences,Guangzhou University,Guangzhou 510006,China;Department of Plant and Microbial Biology,University of California,Berkeley 94720,CA,USA

植物学报（英文版）

[1]Chengbin Xiao;Doudou Sun;Beibei Liu;Xianming Fang;Pengcheng Li;Yao Jiang;Mingming He;Jia Li;Sheng Luan;Kai He-.Nitrate transporter NRT1.1 and anion channel SLAH3 form a functional unit to regulate nitrate-dependent alleviation of ammonium toxicity OO)[J].植物学报（英文版）,2022(04):942-957

SLAH3,NH4+often,NH4+detoxification,nrt1

Nitrate,transporter,NRT1,anion,channel,form,functional,unit,nitrate,dependent,alleviation,ammonium,toxicity,OO,Ammonium,NO3,major,inorganic,nitrogen,sources,plants,When,serving,sole,dominant,supply,causes,root,inhibition,shoot,chlorosis,usually,can,mitigate,even,low,concentrations,referred,Our,previous,studies,indicated,efflux,involved,this,process,How,ever,whether,additional,components,contribute,mediated,unknown,Previously,mutations,were,shown,enhanced,resistance,high,Whereas,study,found,when,medium,was,plemented,mutant,showed,hyper,sensitive,phenotype,instead,Furthermore,caused,acidification,under,condition,suggesting,regulates,by,facilitating,H+,uptake,Moreover,interact,complex,Interestingly,appeared,affect,influx,while,influenced,each,other,protein,gene,expression,levels,thus,revealed,through,regulating,balancing,rhizosphere

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