Identification of Fe-excess-induced genes in rice shoots reveals a WRKY transcription factor responsive to Fe, drought and senescence

Abstract

Fe participates in several important reactions in plant metabolism. However, Fe homeostasis in plants is not completely understood, and molecular studies on Fe-excess stress are scarce. Rice (Oryza sativa L. ssp. indica) is largely cultivated in submerged conditions, where the extremely reductive environment can lead to severe Fe overload. In this work, we used representational difference analysis (RDA) to isolate sequences up-regulated in rice shoots after exposure to Fe-excess. We isolated 24 sequences which have putative functions in distinct cellular processes, such as transcription regulation (OsWRKY80), stress response (OsGAP1, DEAD-BOX RNA helicase), proteolysis (oryzain-α, rhomboid protein), photosynthesis (chlorophyll a/b binding protein), sugar metabolism (β glucosidase) and electron transport (NADH ubiquinone oxireductase). We show that the putative WRKY transcription factor OsWRKY80 is up-regulated in rice leaves, stems and roots after Fe-excess treatment. This up-regulation is also observed after dark-induced senescence and drought stress, indicating that OsWRKY80 could be a general stress-responsive gene. To our knowledge, this is the first report of an Fe-excess-induced transcription factor in plants.

Metal Ion Homeostasis Mediated by NRAMP Transporters in Plant Cells - Focused on Increased Resistance to Iron and Cadmium Ion

“…In plants, it is essential for chlorophyll synthesis and hence iron deficiency results in chlorosis and pale-yellow or white leaves (Wiedenhoeft 2006). Usually, iron is chelated to organic matter in insoluble forms in soils that causes iron deficiency whereas in anaerobic and acidic conditions, iron toxicity occurs because of the increase of iron solubility (Ricachenevsky et al 2010). The basis of iron toxicity was usually discussed to be oxidative stress by generation of reactive-hydroxyl radicals (Neyens and Baeyens 2003).…”

Research Article Iron excess in rice: from phenotypic changes to functional genomics of WRKY transcription factors.

“…This is the third report linking WRKYs with iron excess response (Ricachenevsky et al, 2010;Finatto et al, 2015). The first shows that OsWRKY80, which is also involved in rice drought response and senescence, increases its transcriptional expression (3-fold) after 6 DUS at 500 ppm (Ricachenevsky et al, 2010).…”

“…This is the third report linking WRKYs with iron excess response (Ricachenevsky et al, 2010;Finatto et al, 2015). The first shows that OsWRKY80, which is also involved in rice drought response and senescence, increases its transcriptional expression (3-fold) after 6 DUS at 500 ppm (Ricachenevsky et al, 2010). The second is a microarray analysis showing that 19 WRKYs are up-regulated when rice is under iron excess (7 mM for 18 DUS), suggesting that this family can perform an important role in iron homeostasis (Finatto et al, 2015).…”

“…It is estimated that Fe excess can cause yield losses of up to 400 kg/ha, losses that are strongly correlated with the symptom of leaf bronzing (Audebert and Fofana, 2009). Although this problem can cause deep consequences to the agricultural economy, little is known about the molecular mechanisms involved in the response to Fe excess (Ricachenevsky et al, 2010). The study of transcription factors (TFs) is of great importance in improving plant stress tolerance, since these genes can regulate the expression of many others, resulting in deep physiological modifications (Banerjee and Roychoudhury, 2015).…”

A WRKY Transcription Factor Regulates Fe Translocation under Fe Deficiency

“…Interestingly, W-boxes, the DNA binding sites of WRKY proteins, are enriched in the promoters of many Fe deficiency-responsive genes . Although some rice (Oryza sativa) WRKY genes may play a role in response to Fe excess stress possibly through responding to disturbed redox homeostasis (Ricachenevsky et al, 2010), little is known about whether WRKY proteins take part in Fe deficiency responses. Among total WRKY genes present in public microarray data, there are five WRKYs that are responsive to Fe deficiency at transcript levels (Supplemental Fig.…”