Molybdenum metabolism in plants and crosstalk to iron

Abstract

In the form of molybdate the transition metal molybdenum is essential for plants as it is required by a number of enzymes that catalyze key reactions in nitrogen assimilation, purine degradation, phytohormone synthesis, and sulfite detoxification. However, molybdate itself is biologically inactive and needs to be complexed by a specific organic pterin in order to serve as a permanently bound prosthetic group, the molybdenum cofactor, for the socalled molybdo-enyzmes. While the synthesis of molybdenum cofactor has been intensively studied, only little is known about the uptake of molybdate by the roots, its transport to the shoot and its allocation and storage within the cell. Yet, recent evidence indicates that intracellular molybdate levels are tightly controlled by molybdate transporters, in particular during plant development. Moreover, a tight connection between molybdenum and iron metabolisms is presumed because (i) uptake mechanisms for molybdate and iron affect each other, (ii) most molybdo-enzymes do also require iron-containing redox groups such as iron-sulfur clusters or heme, (iii) molybdenum metabolism has recruited mechanisms typical for iron-sulfur cluster synthesis, and (iv) both molybdenum cofactor synthesis and extramitochondrial iron-sulfur proteins involve the function of a specific mitochondrial ABC-type transporter.

Expression of Some Molybdoenzyme Genes under Salt Stress Conditions in Chickpea, Bean and Lentil Plants

“…In chickpea we couldn't observe any expression of the gene. Bittner, 2014). the difference between the two mARC isoforms gene expression in bean plants with the expression of the housekeeping gene actin, obviously the two isoform express differently, we used ImageJ to better appreciate the intensity (table.3) Research on NCBI leads us to two mARC isoforms; mARC1 and mARC2 in bean species, early work on mARC indicates that depending on species, usually one isoform is predominantly expressed (Plitzko et al, 2013), as we can see ( figure. 2) the two isoform express differently, the highest value of mARC1 intensity is 1,031represented by the control, that means that adding molybdenum or nitrogen doesn't enhance mARC1 gene expression, and salt stress may lead to a decrease in its protein expression, the contrary happens in mARC2; so we can observe that the most important value is 1,021 (table3) registered for bean plant that are submitted to a salt stress adding molybdenum and nitrogen, comparing to the lowest value which represent control plants.…”

“…XDH takes part in a purine metabolism and also in biosynthesis of ureides in higher plants; ureides like urea, as "scavengers", could remove oxygen radicals, which are formed under stress conditions (Sagi et al, 1998) Aldehyde oxidase gene (AAO3) doesn't show any expression in bean plants but in chickpea we can observe an intense expression when molybdenum and nitrogen are added to plant irrigation water, (Tab.4).The most important isoformis AAO3,whichcatalyzes the oxidation of abscisicaldehyde to abscisicacid(ABA) in the last cytosolicstep of ABA synthesis. Due to the function of ABA in many aspects of plant growth and development, andin adaptation to a variety of abiotic stresses, AAO3-deficient plantswithreduced ABA levels are characterized by a high transpirationrate, reduced stress tolerance, and impairedseeddormancy (Seoand Koshiba, 2011in Bittner (2014). Xanthine dehydrogenase (XDH1) is well expressed in bean plants under salt stress and with Mo and N added, (Table 3) and has the lowest expression in control plants, but in chickpea the highest expression of this gene is observed in plants receiving Mo and N in their water irrigation without any stress condition ( (Bittner, 2014) In bean, ABA3/LOS5 gene expression is affected by salinity, as we note on Table 3, control plants have the most important value of band intensity, this expression in affected by salinity, but not enhanced by Mo or N added.…”

“…Due to the function of ABA in many aspects of plant growth and development, andin adaptation to a variety of abiotic stresses, AAO3-deficient plantswithreduced ABA levels are characterized by a high transpirationrate, reduced stress tolerance, and impairedseeddormancy (Seoand Koshiba, 2011in Bittner (2014). Xanthine dehydrogenase (XDH1) is well expressed in bean plants under salt stress and with Mo and N added, (Table 3) and has the lowest expression in control plants, but in chickpea the highest expression of this gene is observed in plants receiving Mo and N in their water irrigation without any stress condition ( (Bittner, 2014) In bean, ABA3/LOS5 gene expression is affected by salinity, as we note on Table 3, control plants have the most important value of band intensity, this expression in affected by salinity, but not enhanced by Mo or N added. In chickpea we couldn't observe any expression of the gene.…”

“…Moreover, molecular. ( Bittner, 2014) Aldehyde oxidase (AO; EC 1.2.3.1) and xanthine dehydrogenase (XDH; EC 1.2.1.37) are known to take part in processes connected with the adaptation of living organisms to stress conditions. So, for example, АОcatalyzes the last stages in biosynthesis of two phytohormones; oxidation of abscisic aldehyde up to abscisic acid and oxidation of indole-3-acetaldehyde up to indole-3-acetic acid (Walker-Simmons et al, 1989, and Koshiba et al, 1996).…”

From soil to seed: micronutrient movement into and within the plant

“…Socha and Guerinot (2014) provide a comprehensive review of the transporters with potential roles in manganese (Mn) transport including information about their localization and regulation by Mn toxicity or deficiency. Molybdenum (Mo) metabolism is presented by Bittner (2014), including transporters and Mo cofactor (Moco)-dependent proteins, as well as the yet to be fully understood crosstalk between Mo and Fe metabolism. Finally, the role of metals in nodulation and symbiotic nitrogen fixation is presented by González-Guerrero et al (2014), providing an overview of the role of different elements, metalloproteins and metal cofactors for nodule formation and function, and discussing contributions of distinct transporters for metal uptake, accumulation and spatial distribution within the nodules.…”