Response of Arabidopsis to Iron Deficiency Stress as Revealed by Microarray Analysis

Abstract

Gene expression in response to Fe deficiency was analyzed in Arabidopsis roots and shoots through the use of a cDNA collection representing at least 6,000 individual gene sequences. Arabidopsis seedlings were grown 1, 3, and 7 d in the absence of Fe, and gene expression in roots and shoots was investigated. Following confirmation of data and normalization methods, expression of several sequences encoding enzymes known to be affected by Fe deficiency was investigated by microarray analysis. Confirmation of literature reports, particularly for changes in enzyme activity, was not always possible, but changes in gene expression could be confirmed. An expression analysis of genes in glycolysis, the tricarboxylic acid cycle, and oxidative pentose phosphate pathway revealed an induction of several enzymes within 3 d of Fe-deficient growth, indicating an increase in respiration in response to Fe deficiency. In roots, transcription of sequences corresponding to enzymes of anaerobic respiration was also induced, whereas in shoots, the induction of several genes in gluconeogenesis, starch degradation, and phloem loading was observed. Thus, it seemed likely that the energy demand in roots required for the Fe deficiency response exceeded the capacity of oxidative phosphorylation, and an increase in carbon import and anaerobic respiration were required to maintain metabolism.

Carboxylate metabolism changes induced by Fe deficiency in barley, a Strategy II plant species

“…Barley leaves did not show increases in PEPC or CS activities with Fe deficiency, in contrast to what has been reported in other Strategy I species, with the only consistent changes with Fe deficiency among cultivars being the increases in fumarase and G6PDH activities (also reported in sugar beet Fe-deficient leaves) and a decrease in aconitase activity (not occurring in Strategy I plants). These results suggest that the increased carboxylate pool in leaves could be associated with an influx of carbon from the root system via xylem flow, as has been proposed for Fe-deficient leaves of sugar beet, tomato, and pear, although a contribution of the metabolic alterations measured here (e.g., lower aconitase and higher fumarase activities) cannot be fully excluded (López-Millán et al, 2000a,b, 2001.…”

“…The activity of LDH was approximately 30% (Table 1). These two enzymes have been used as markers of anaerobiosis, and have been previously described to be induced in Strategy I Fe-deficient roots at the expression, protein accumulation, and enzyme activity levels (López-Millán et al, 2009;Thimm et al, 2001;Donnini et al, 2010). The concentration of total carboxylates was 100% higher in Steptoe and 160% higher in Morex Fe-deficient roots than in Fe-sufficient controls.…”

“…These changes include an accumulation of organic acids throughout the plant, mainly malate and citrate (reviewed in Abadía et al, 2002), increases in the activity of PEPC and in several enzymes of the Krebs cycle and of the glycolytic and pentose phosphate pathways (Zocchi, 2006). Some increased activities are associated with enhanced expression of the corresponding genes (Thimm et al, 2001). This metabolic reprogramming could also act as an anaplerotic source to overcome the low photosynthetic rates in Fedeficient Strategy I plants (López-Millán et al, 2009).…”

Acquisition and Homeostasis of Iron in Higher Plants and Their Probable Role in Abiotic Stress Tolerance

“…Fe deficiency in plants causes interveinal chlorosis (Bienfait and Van der Mark, 1983), poor root development, growth retardation, and the eventual death of the plant (Kobayashi et al, 2003). In addition, Fe deficiency also leads to the alteration in expression of chlorophyll-binding proteins and the down-regulation of many photosynthetic pigment levels (Thimm et al, 2001;Rout and Sahoo, 2015). In the agricultural soils, Fe deficiency may also occur either at extremely high pH or at extremely low pH levels.…”

Transcriptional Profiling of the Arabidopsis Iron Deficiency Response Reveals Conserved Transition Metal Homeostasis Networks

“…Fe deficiency is associated with alterations in several metabolic pathways in both roots and shoots that lead to, among other alterations in metabolic profiles, an increase in CO 2 dark fixation and an accumulation of organic acids in roots, in particular citrate (Thimm et al, 2001;Buckhout and Thimm, 2003;Zocchi et al, 2007;López-Millán et al, 2009). Whether these changes represent adaptations to Fe deficiency or merely reflect imbalances between carbon metabolism and energy-generating reactions remains obscure.…”