Discovering the role of mitochondria in the iron deficiency-induced metabolic responses of plants

Abstract

In plants, iron (Fe) deficiency-induced chlorosis is a major problem, affecting both yield and quality of crops. Plants have evolved multifaceted strategies, such as reductase activity, proton extrusion, and specialised storage proteins, to mobilise Fe from the environment and distribute it within the plant. Because of its fundamental role in plant productivity, several issues concerning Fe homeostasis in plants are currently intensively studied. The activation of Fe uptake reactions requires an overall adaptation of the primary metabolism because these activities need the constant supply of energetic substrates (i.e., NADPH and ATP). Several studies concerning the metabolism of Fe-deficient plants have been conducted, but research focused on mitochondrial implications in adaptive responses to nutritional stress has only begun in recent years. Mitochondria are the energetic centre of the root cell, and they are strongly affected by Fe deficiency. Nevertheless, they display a high level of functional flexibility, which allows them to maintain the viability of the cell. Mitochondria represent a crucial target of studies on plant homeostasis, and it might be of interest to concentrate future research on understanding how mitochondria orchestrate the reprogramming of root cell metabolism under Fe deficiency. In this review, I summarise what it is known about the effect of Fe deficiency on mitochondrial metabolism and morphology. Moreover, I present a detailed view of the possible roles of mitochondria in the development of plant responses to Fe deficiency, integrating old findings with new and discussing new hypotheses for future investigations.

AUX1 and PIN2 Protect Lateral Root Formation in Arabidopsis under Fe Stress

“…Several studies have indicated that nutrients, such as N and P, with heterogeneous distribution in the soil and rhizosphere (Hodge, 2004;Britto and Kronzucker, 2013;Hufnagel et al, 2014), are sensed by root-localized mechanisms (Forde and Lorenzo, 2001;Forde and Walch-Liu, 2009). Iron toxicity as a syndrome in plants is typically associated with an excessive amount of the ferrous form (the Fe 2+ ion) in the soil (Vigani, 2012). The presence of the Fe 2+ ion is increased by low pH and hypoxic or anoxic conditions, and there is an increasing presence in vertically lower strata (Ratering and Schnell, 2000;Becker and Asch, 2005).…”

“…Such a change may adjust root system architecture to restrict excessive Fe absorption, which also occurs predominantly in the Fe 2+ form (Vigani, 2012;Li et al, 2015), and prevent serious Fe toxicity. In addition, relatively stable LR number and length in the branching zone, or the proximal root portions, helped by Fe sequestration in the vacuole and by components such as ferritins (Vigani, 2012;Reyt et al, 2015), may play a role in maintaining the absorption of other nutrients in the less stressed areas of the root system.…”

Relationship between tree nutritional status and apple quality

“…Zocchi (2006) and Vigani (2012) noted that the metabolic Fe deficiency level induced several changes, mainly concerning carbon (C) and nitrogen (N) metabolism, because the metabolism of these two elements (C, N) are strongly interrelated. Borlotti et al (2012) reported that Fe deficiency had a differential effect on N metabolism in roots and leaves, with particular adaptive mechanisms to nutritional constraint acting at the whole plant level.…”

Increased de novo riboflavin synthesis and hydrolysis of FMN are involved in riboflavin secretion from Hyoscyamus albus hairy roots under iron deficiency

“…In particular, plants growing on calcareous soils are at risk of Fe deficiency because although ferric ions are often abundant in these soils they are largely unavailable to plant roots, owing to the extremely low solubility of ferric compounds. Therefore, mechanisms for the avoidance or correction of Fe deficiency in plants have been intensively studied [6][7][8][9][10]. However, it is not yet known why or how some plant species secrete flavins from their roots under conditions of Fe deficiency.…”