Cadmium exposure affects iron acquisition in barley (Hordeum vulgare) seedlings

Abstract

This study addresses the question of the interference between iron (Fe) nutrition and cadmium (Cd) toxicity at the level of growth performance, phytosiderophores (PS) release, micronutrient accumulation and expression of genes involved in Fe homeostasis in barley seedlings, a plant with strategy II-based response to Fe shortage. Cd exposure induced responses similar to those of genuine Fe deficiency also in Fe-sufficient plants. Most genes involved in PS biosynthesis and secretion (HvNAS3, HvNAS4, HvNAS6, HvNAS7, HvNAAT-A, HvDMAS1 and HvTOM1) induced by Fe deprivation were also significantly upregulated in the presence of Cd under Fe sufficient conditions. Accordingly, the enhanced expression of these genes in roots under Cd exposure was accompanied by an increase of PS release. However, induced expression of HvIRO2 and the downregulation of HvIDEF1 and HvIRT1, after Cd exposure, suggested the presence of a pathway that induces HvIRO2-mediated PS biosynthesis under Cd stress, which probably is not simply caused by Fe deficiency. The downregulation of HvIRT1 and HvNramp5 may represent a protective mechanism at transcriptional level against further Cd uptake by these transporters. These results likely indicate that Cd itself may be able to activate Fe acquisition mechanism in an Fe-independent manner.

Release of phytosiderophores from roots of wheat and triticale under nickel‐deficient conditions

“…Such mechanisms have also proposed by Astolfi et al. () for Cd and Fe. Their results showed that Cd exposure under adequate Fe supply can induce an Fe deficiency‐like response in barley.…”

“…It is proposed that Ni itself may be able to interfere with the Zn and Fe acquisition and transport mechanism in Rushan. Such mechanisms have also proposed by Astolfi et al (2014) for Cd and Fe. Their results showed that Cd exposure under adequate Fe supply can induce an Fe deficiency-like response in barley.…”

The expression of heterologous Fe (III) phytosiderophore transporter HvYS1 in rice increases Fe uptake, translocation and seed loading and excludes heavy metals by selective Fe transport

“…The decrease in Cd seed concentration is particularly important given the simultaneous 2‐fold increase in Fe levels, because such an approach would simultaneously address the issues of Fe deficiency and Cd toxicity in rice fields with low‐Fe/high‐Cd soils (Clemens et al ., ; Slamet‐Loedin et al ., ). Our results show that plants can take up more Fe in the presence of Cd, and Fe acquisition in the presence of Cd may thus act as a defence mechanism to mitigate Cd‐induced stress (Astolfi et al ., ; Meda et al ., ). Similarly, overexpression of the plastid Fe transporter gene NtPIC1 in tobacco boosted the Fe/Cd ratio in leaves and improved Cd tolerance (Gong et al ., ), and rice expressing HvNAS1 and OsNAS1 + HvNAATb also accumulated more Fe but less Cd in the seeds compared to wild‐type plants (Masuda et al ., ; Banakar et al., under review).…”

Regulation of Phytosiderophore Release and Antioxidant Defense in Roots Driven by Shoot-Based Auxin Signaling Confers Tolerance to Excess Iron in Wheat

“…Also, expression of genes involved in the synthesis of MA ( HvNAAT-A and HvDMAS1 ) and in the Fe uptake ( HvTOM1, HvYS1, HvIRT1, HvNramp2, HvNramp5 , and HvNarmp7 ) in barley upon Fe deficiency (Astolfi et al, 2010, 2014). However, DMA is also detected in Fe-sufficient shoot in rice possibly involved in Fe translocation as Fe-DMA complex (Mori et al, 1991).…”