Nitrate transporters in leaves and their potential roles in foliar uptake of nitrogen dioxide†

Abstract

While plant roots are specialized organs for the uptake and transport of water and nutrients, the absorption of gaseous or liquid mineral elements by aerial plant parts has been recognized since more than one century. Nitrogen (N) is an essential macronutrient which generally absorbed either as nitrate (NO−3) or ammonium (NH+4) by plant roots. Gaseous nitrogen pollutants like N dioxide (NO2) can also be absorbed by plant surfaces and assimilated via the NO−3 assimilation pathway. The subsequent NO−3 flux may induce or repress the expression of various NO−3-responsive genes encoding for instance, the transmembrane transporters, NO−3/NO−2 (nitrite) reductase, or assimilatory enzymes involved in N metabolism. Based on the existing information, the aim of this review was to theoretically analyze the potential link between foliar NO2 absorption and N transport and metabolism. For such purpose, an overview of the state of knowledge on the NO−3 transporter genes identified in leaves or shoots of various species and their roles for NO−3 transport across the tonoplast and plasma membrane, in addition to the process of phloem loading is briefly provided. It is assumed that a NO2-induced accumulation of NO−3/NO−2 may alter the expression of such genes, hence linking transmembrane NO−3 transporters and foliar uptake of NO2. It is likely that NRT1/NRT2 gene expression and species-dependent apoplastic buffer capacity may be also related to the species-specific foliar NO2 uptake process. It is concluded that further work focusing on the expression of NRT1 (NRT1.1, NRT1.7, NRT1.11, and NRT1.12), NRT2 (NRT2.1, NRT2.4, and NRT2.5) and chloride channel family genes (CLCa and CLCd) may help us elucidate the physiological and metabolic response of plants fumigated with NO2.

More Transporters, More Substrates: The Arabidopsis Major Facilitator Superfamily Revisited

“…The family subdivides into eight subfamilies, NPF1-8, the largest of which are NPF2 and NPF5. The functions of NPFs as nitrate transporters have recently been reviewed in detail (Wang et al, 2012;Hu et al, 2014;Kiba and Krapp, 2016;Wen and Kaiser, 2018).…”

Inhibition of Echinochloa crus-galli using Bioactive Components from the Stems and Leaves of Camellia oleifera

“…On the other hand, Nitrogen (N) is an essential macronutrient, generally absorbed as either nitrate (NO3 -) or ammonium (NH 4+ ) in plant roots. Gaseous nitrogen pollutants, such as N dioxide (NO2), are also absorbed by plant surfaces and assimilated via the NO3assimilation pathway (Hu et al, 2014), Inhibition of A1 fraction to amino acid content disturbed the barnyardgrass's metabolism of substances and energy. The research results suggest that the A1 fraction decreases both root activity and N acquisition, thus affecting root growth and the development of barnyardgrass.…”

Measurement report: Leaf-scale gas exchange of atmospheric reactive trace species (NO<sub>2</sub>, NO, O<sub>3</sub>) at a northern hardwood forest in Michigan

“…The enclosed branch was in the upper part of the crown containing developing new leaves. Past measurements, albeit on different species, have shown that for the same species under similar environmental conditions, leaves of young trees generally have higher stomatal conductance than old ones (Niinemets, 2002;Hubbard et al, 1999;Fredericksen et al, 1995;Yoder et al, 1994). Another possible reason for the observed high g H 2 O , while direct evidence has yet to be found, is the number of stomata.…”

“…The uptake efficiency varies across plants and is influenced by environmental conditions. Studies at leaf level and within leaves have found that after entering the stomata, NO 2 is metabolized through dissolution and enzyme-catalyzed reactions (Hu et al, 2014;Vallano and Sparks, 2008;Weber et al, 1998;Nussbaum et al, 1993). Unlike NO 2 and O 3 , foliar exchange of NO is small to insignificant (Hereid and Monson, 2001;Rondón et al, 1993), except for herbicide-treated soybeans (Klepper, 1979) and nutrient-fed sugar cane, sunflower, corn, spinach, and tobacco plants (Wildt et al, 1997), where NO emission was observed.…”