SelectedAspects of Iodate and Iodosalicylate Metabolism in Lettuce Including the Activity of Vanadium Dependent Haloperoxidases as Affected by Exogenous Vanadium

Abstract

In marine algae, vanadium (V) regulates the cellular uptake of iodine (I) and its volatilization as I2, the processes catalyzed by vanadium-dependent haloperoxidases (vHPO). Relationships between I and vanadium V in higher plants, including crop plants, have not yet been described. Little is known about the possibility of the synthesis of plant-derived thyroid hormone analogs (PDTHA) in crop plants. The activity of vHPO in crop plants as well as the uptake and metabolism of iodosalicylates in lettuce have not yet been studied. This studyaimed to determine the effect of V on the uptake and accumulation of various forms of I, the metabolism of iodosalicylates and iodobenzoates and, finally, on the accumulation of T3 (triiodothyronine—as example of PDTHA) in plants. Lettuce (Lactuca sativa L. var. capitata ‘Melodion’ cv.) cultivation in a hydroponic NutrientFilm Technique (NFT) system was conducted with the introduction of 0 (control), 0.05, 0.1, 0.2, and 0.4 µM V doses of ammonium metavanadate (NH4VO3) in four independent experiments. No iodine treatment was applied in Experiment No. 1, while iodine compounds were applied at a dose of 10 µM (based on our own previous research) as KIO3, 5-iodosalicylic acid (5-ISA) and 3,5-diiodosalicylic acid (3,5-diISA) in Experiment Nos. 2, 3 and 4, respectively. When lettuce was grown at trace amount of I in the nutrient solution, increasing doses of V contributed to the increase of (a) I content in roots, (b) I uptake by whole lettuce plants (leaves + roots), and (c) vHPO activity in leaves (for doses 0.05–0.20 µM V). Vanadium was mainly found in roots where the content of this element increased proportionally to its dose. The content of V in leaves was not modified by V introduced into the nutrient solution. We found that5-ISA, 3,5-diISA and T3 were naturally synthesized in lettuce and its content increased when 5-ISA, 3,5-diISA were applied. Quantitative changes in the accumulation of organic metabolites (iodosalicylates and iodobenzoates) accumulation were observed, along with increased T3 synthesis, with its content in leaves exceeding the level of individual iodosalicylates and iodobenzoates. The content of T3 was not affected by V fertilization. It was concluded that iodosalicylates may participate in the biosynthesis pathway of T3—and probably of other PDTHA compounds.

Joint Selenium–Iodine Supply and Arbuscular Mycorrhizal Fungi Inoculation Affect Yield and Quality of Chickpea Seeds and Residual Biomass

“…Innovatively, the findings from the present research reveal the significant role of AMF in enhancing the I, Se, and Se + I effect on chickpea plants. This phenomenon is of special interest due to the intensive investigation of factors that can improve the combined Se + I biofortification [18,21,22]. The AMF stimulation of Se and I accumulation in chickpea seeds may be partially connected with two processes: the increase in root surface, which encourages nutrient accumulation, and the specific AMF action inside the plant.…”

“…The AMF stimulation of Se and I accumulation in chickpea seeds may be partially connected with two processes: the increase in root surface, which encourages nutrient accumulation, and the specific AMF action inside the plant. Interestingly, the AMF utilization seems to open new chances in Se/I fortification, considering that thus far only the application of phytohormones such as salicylic acid [17,21] and the vanadium compounds that participate to iodine metabolism of marine algae [22] have been investigated.…”

“…In general, the results of the previous investigations indicated a complex relationship between Se and I and a much higher efficiency of Se accumulation compared to that of I, with no effect on growth stimulation by the application of Se and I combined. In this respect, the utilization of marine algae [19,20], salicylic acid [21], and vanadium salt application [22] was employed to improve the efficiency of joint I and Se plant enrichment. However, to date, no efforts have been made to test the efficiency of arbuscular mycorrhizal fungi (AMF) inoculation.…”

Evidences for a nutritional role of iodine in plants

“…Iodine can be found in plant tissues not only in a mineral form but also in organic compounds (Wang, Zhou, Fredimoses, Liao & Liu, 2014;Smoleń et al, 2020). To verify the possible in vivo incorporation of iodine into proteins, we carried out two different experiments by feeding hydroponically grown plants with 125 I and carrying out the autoradiography of the SDS-PAGE of the relative protein extracts to detect possible radio-labelled proteins.…”

“…Inorganic iodine, iodide (I -), however, seems to be predominant (Weng et al, 2008). Plants can also incorporate iodine into organic molecules, such as T3 or mono-iodotyrosine (MIT) and di-iodotyrosine (DIT), which are precursors of T3 and T4 THs in vertebrates (Eales, 1997;Smoleń et al, 2020). The metabolic role of these molecules and their biosynthetic mechanism are still unknown.…”