The Effect of the Upregulated Expression of Fe Regulators IMA1 and bHLH104 in Arabidopsis on the Root Length and Fe Homeostasis Under Pi Starvation
Abstract Phosphate (Pi) and iron (Fe) are two essential mineral nutrients for plant growth and development. Pi starvation triggers the Fe local redistribution and over-accumulation, resulting in the reduction of the primary root, while represses the expression of Fe uptake genes. Nevertheless, the antagonistic mechanism between P and Fe nutrition in plant remain not addressed. Here, the effect of the upregulated expression of Fe regulators IMA1 and bHLH104 driven by the different-type promoters (proCaMV 35S, the promoters of Pi-starvation responsive genes proIPS1 and proPHT1;4) in response to Pi starvation was investigated in Arabidopsis. The results showed that the expression of Fe uptake genes IRT1 and FRO2 was successfully upregulated in proIPS1::IMA1, proPHT1;4::IMA1 and proIPS1::bHLH104 under Pi starvation while decreased in pro35S::IMA1, pro35S::bHLH104 and proPHT1;4::bHLH104, compared with that in the corresponding plants under Pi sufficiency. Although the length and Fe distribution in roots of them didn’t have significant difference with wild type under Pi starvation, the Fe distribution and total Fe contents were significantly increased in shoots of proIPS1::IMA1, proPHT1;4::IMA1 and proIPS1::bHLH104 while were decreased in proPHT1;4::bHLH104. The higher Fe concentrations in the Pi-starved transgenic plants also conferred the obviously tolerance to Fe deficiency. Their biomasses and total P concentrations showed no difference with wild type, regardless of Pi sufficiency or deficiency. Therefore, this approach would be a novel manipulation to modify Fe nutrient via coupling with Pi starvation in plants.