Biosynthesis and secretion of mugineic acid family phytosiderophores in zinc‐deficient barley

Abstract

SummaryMugineic acid family phytosiderophores (MAs) are metal chelators that are produced in graminaceous plants in response to iron (Fe) deficiency, but current evidence regarding secretion of MAs during zinc (Zn) deficiency is contradictory. Our studies using HPLC analysis showed that Zn deficiency induces the synthesis and secretion of MAs in barley plants. The levels of the HvNAS1, HvNAAT-A, HvNAAT-B, HvIDS2 and HvIDS3 transcripts, which encode the enzymes involved in the synthesis of MAs, were increased in Zn-deficient roots. Studies of the genes involved in the methionine cycle using microarray analysis showed that the transcripts of these genes were increased in both Zn-deficient and Fe-deficient barley roots, probably allowing the plant to meet its demand for methionine, a precursor in the synthesis of MAs. In addition, HvNAAT-B transcripts were detected in Zn-deficient shoots, but not in those that were deficient in Fe. Increased synthesis of MAs in Zndeficient barley was not due to a deficiency of Fe, because Zn-deficient barley accumulated more Fe than did the control plants, ferritin transcripts were increased in Zn-deficient plants, and Zn deficiency promoted Fe transport from root to shoot. Moreover, analysis using the positron-emitting tracer imaging system (PETIS) confirmed that more 62 Zn(II)-MAs than 62 Zn 2þ were absorbed by the roots of Zn-deficient barley plants. These data suggest that the increased biosynthesis and secretion of MAs arising from a shortage of Zn are not due to an induced Fe deficiency, and that secreted MAs are effective in absorbing Zn from the soil.

Increase in Iron and Zinc Concentrations in Rice Grains Via the Introduction of Barley Genes Involved in Phytosiderophore Synthesis

“…Interestingly, the Zn concentration was also higher in gIDS3 seeds than in the seeds of NT and other transgenic lines. DMA is involved in the long-distance transport of Zn in Zn-deficient barley and rice [21,22]. In addition, the structure of the MAs-Zn(II) complex is very similar to that of MAs-Fe(III) [27].…”

Generation and Field Trials of Transgenic Rice Tolerant to Iron Deficiency

“…Recent application of microarray techniques reconfirmed the induction of the abovementioned genes involved in MAs biosynthesis in Fe-deficient barley roots [41,56]. The microarray approach also resulted in cloning of DMAS genes from rice (OsDMAS1), barley (HvDMAS1), wheat (TaDMAS1), and maize (ZmDMAS1).…”

“…We also applied a revised differential hybridization screening, identifying iron-deficiency-induced (IDI) genes from barley roots [70][71][72]. IDI1 and IDI2 putatively encode enzymes catalyzing steps in the methionine cycle [26,56].…”

Plants Root Interference Area, A Benefit To The Microbial Community

“…Many studies have reported higher numbers of bacteria in the area influenced by the root system, compared to the free of roots soil, localized mainly at the base and at the tips of the root system (Tesařová and Rěpová, 1984 In terms of microbial diversity, it was noticed that in the area of plants influenced soil, especially dominate the proteobacteria and actinobacteria (Suzuki et al, 2006;Singh et al, 2007), which are the most studied. Microorganisms are influenced by an accumulation of abiotic and biotic factors that lead to numerical and qualitative variations, observed by Graystonet al (1998).…”