Flavin excretion from roots of iron-deficient sugar beet (Beta vulgaris L.)

Abstract

Abstract. The characteristics of flavin excretion from iron-deficient sugar-beet roots have been studied. Roots from iron-deficient sugar beet excreted flavins when plants were allowed to decrease the pH of the nutrient solution, but not when plants were grown in nutrient solutions buffered at high pH. As shown by reversedphase high-performance liquid chromatography, the two major flavins whose excretion was induced by iron deficiency were different from riboflavin, FMN and FAD. These flavins have been identified as riboflavin 3'-sulfate and riboflavin 5'-sulfate by electrospray-mass spectrometry, inductively coupled plasma emission spectroscopy, infrared spectrometry and 1H-nuclear magnetic resonance. We have characterized the time courses of accumulation of the different flavins in the nutrient solution and considered several possible roles for flavin excretion in iron acquisition.

Root tip-dependent, active riboflavin secretion by Hyoscyamus albus hairy roots under iron deficiency

“…In the case of H. niger root cultures, the minimum pH was between 4.4~4.6 [36]. In sugar beet [34], pH reached approximately 3.7 after 15days, and pH was maintained at 3.5~4.0 in muskmelon [10]. In H. albus hairy roots, the minimum pH was around 4.0 when a single root tip was subjected to iron deficiency and around 4.5 when propagated roots did.…”

“…It was also found that not all but some strategy I plants from Aizoceae to Umbelliferae, including tobacco, beet, sunflower and cucumber, excrete riboflavin [39], and also unique riboflavin sulfates in the case of sugar beet [33,34], in the rhizosphere under iron-deficient conditions. Recently, cultured roots of Hyoscyamus niger were also found to be able to secrete riboflavin without their aerial parts [36].…”

Improved iron acquisition ofAstragalus sinicusunder low iron-availability conditions by soil-borne bacteriaBurkholderia cepacia

“…Under Fe deficiency, the Arabidopsis plants secrete Fe-mobilizing phenolic compounds such as coumarins to acquire Fe by chelation and/ or reduction of Fe 3+ (Fourcroy et al 2014). Besides phenolics, some plant species such as sugar beet, spinach and alfalfa can synthesize and release abundant flavins that play redox and/or metal-complexing roles in augmenting Fe mobilization in the rhizosphere (Susín et al 1993(Susín et al , 1994Rodríguez-Celma et al 2011). Importantly, some PGPR strains such as Azospirillum brasilense and P. polymyxa BFKC01 can enhance Fe acquisition by increasing root-secreted phenolics (Pii et al 2015;Zhou et al 2016).…”

Identification and expression analysis of multiple FRO gene copies in Medicago truncatula

“…It is known that iron deficiency promotes the excretion of phenolic compounds, organic acids, and flavins, which also contribute to Fe reduction and solubility (Welkie and Miller, 1988;Susín et al, 1994). The FRO gene, is a key enzyme in Fe acquisition, and the first FRO2 gene was identified in the model plant Arabidopsis thaliana (Robinson et al, 1999).…”