Variation in Molybdenum Content Across Broadly Distributed Populations of Arabidopsis thaliana Is Controlled by a Mitochondrial Molybdenum Transporter (MOT1)

Abstract

Molybdenum (Mo) is an essential micronutrient for plants, serving as a cofactor for enzymes involved in nitrate assimilation, sulfite detoxification, abscisic acid biosynthesis, and purine degradation. Here we show that natural variation in shoot Mo content across 92 Arabidopsis thaliana accessions is controlled by variation in a mitochondrially localized transporter (Molybdenum Transporter 1 - MOT1) that belongs to the sulfate transporter superfamily. A deletion in the MOT1 promoter is strongly associated with low shoot Mo, occurring in seven of the accessions with the lowest shoot content of Mo. Consistent with the low Mo phenotype, MOT1 expression in low Mo accessions is reduced. Reciprocal grafting experiments demonstrate that the roots of Ler-0 are responsible for the low Mo accumulation in shoot, and GUS localization demonstrates that MOT1 is expressed strongly in the roots. MOT1 contains an N-terminal mitochondrial targeting sequence and expression of MOT1 tagged with GFP in protoplasts and transgenic plants, establishing the mitochondrial localization of this protein. Furthermore, expression of MOT1 specifically enhances Mo accumulation in yeast by 5-fold, consistent with MOT1 functioning as a molybdate transporter. This work provides the first molecular insight into the processes that regulate Mo accumulation in plants and shows that novel loci can be detected by association mapping.

<i>ABNORMAL SHOOT IN YOUTH</i>, a Homolog of Molybdate Transporter Gene, Regulates Early Shoot Development in Rice

“…Because the Km value of Chlamydomonas CrMOT2 for molybdate is higher than that of Arabidopsis MOT1 and CrMOT1 [24,26], ASY may have a different function from the MOT1-type molybdate transporter. It is possible that ASY creates a local concentration gradient of Mo, which is required for organ development.…”

“…Two genes, MOT1 and MOT2, encode molybdate transporters in Arabidopsis, but they are different from ASY/CrMOT2 [24][25][26][27][28]. In the presence of Mo, the Arabidopsis mot1 mutant does not show severe phenotypes [24,26,29]. In contrast, asy showed more severe phenotypes than Arabidopsis mot1 under appropriate soil conditions (seemingly in the presence of sufficient Mo), suggesting a functional difference between ASY and MOT1.…”

“…The sequence similarity and subcellular localization of ASY suggest that it also acts as a molybdate transporter. Two genes, MOT1 and MOT2, encode molybdate transporters in Arabidopsis, but they are different from ASY/CrMOT2 [24][25][26][27][28]. In the presence of Mo, the Arabidopsis mot1 mutant does not show severe phenotypes [24,26,29].…”

Sulfur Nutrition in Crop Plants

“…In Brassica napus , Sultr5;1 is present in the root, stem, and leaves and is localized in the tonoplast (Hawkesford et al, 2003b ;Parmar et al, 2007 ). In Arabidopsis , transporter AtSultr5;2, appears to be a high -affi nity molybdenum transporter and has been renamed MOT1 (molybdenum transporter 1; Tomatsu et al, 2007 ;Baxter et al, 2008 ).…”

Quantitative trait loci (QTL) and candidate genes associated with trace element concentrations in perennial grasses grown on phytotoxic soil contaminated with heavy metals

“…Likewise, an experimental population derived from metal-tolerant Arabidopsis halleri and non-tolerant Arabidopsis lyrata species was used to identify specific candidate genes associated with differences in uptake of Zn and Cd between these species (Courbot et al 2007;Roosens et al 2008). It has been shown the molybdate transporter 1 (MOT1) gene (Tejada-Jiménez et al 2007;Tomatsu et al 2007) is associated with natural genetic variation in the Mo content of A. thaliana (Baxter et al 2008;Buescher et al 2010) and other dicotyledenous plants (Lowry et al 2012). In some cases, QTL mapping is a useful approach to the discovery of genes controlling heavy metal uptake as demonstrated by the positional cloning of the heavy metal ATPase 3 (HMA3) gene, encoding a defective P 1B -type ATPase, associated with the rice qCdT7 QTL (Tezuka et al 2010;Miyadate et al 2011).…”