Expression of Genes for Si Uptake, Accumulation, and Correlation of Si with Other Elements in Ionome of Maize Kernel.

Boris Bokor,Irene Lichtscheidl,Silvia Bokorová,Alexander Lux,Marek Vaculík,Slavomír Ondoš,Marieluise Weidinger,Ján Turňa

doi:10.3389/fpls.2017.01063

Abstract

The mineral composition of cells, tissues, and organs is decisive for the functioning of the organisms, and is at the same time an indicator for understanding of physiological processes. We measured the composition of the ionome in the different tissues of maize kernels by element microanalysis, with special emphasis on silicon (Si). We therefore also measured the expression levels of the Si transporter genes ZmLsi1, ZmLsi2 and ZmLsi6, responsible for Si uptake and accumulation. Two weeks after pollination ZmLsi1 and ZmLsi6 genes were expressed, and expression continued until the final developmental stage of the kernels, while ZmLsi2 was not expressed. These results suggest that exclusively ZmLsi1 and ZmLsi6 are responsible for Si transport in various stages of kernel development. Expression level of ZmLsi genes was consistent with Si accumulation within kernel tissues. Silicon was mainly accumulated in pericarp and embryo proper and the lowest Si content was detected in soft endosperm and the scutellum. Correlation linkages between the distribution of Si and some other elements (macroelements Mg, P, S, N, P, and Ca and microelements Cl, Zn, and Fe) were found. The relation of Si with Mg was detected in all kernel tissues. The Si linkage with other elements was rather specific and found only in certain kernel tissues of maize. These relations may have effect on nutrient uptake and accumulation.

Highlights

The composition of minerals in a cell, tissue, or the whole organism is referred to as the ionome
Expression of ZmLsi genes was detected in maize kernel at the 1st developmental stage 2 weeks after pollination (Figure 2)
That ZmLsi1 and ZmLsi6 expression occurred in maize kernel, while the ZmLsi2 gene was not expressed during kernel development at all

Summary

Introduction

The composition of minerals in a cell, tissue, or the whole organism is referred to as the ionome. Element tissue composition can vary greatly upon various abiotic stress conditions such as metal toxicity as it was found out in maize root and shoot (Bokor et al, 2015). In those plants, the root ionome was much more affected than the shoot ionome due to Zn exposure, and, surprisingly, by Si application, with lower intensity. Understanding of relationships between elements is crucial to unravel the regulation of ionome These relationships can exist regardless of the tissue, species, or environment; many associations will vary with a combination of these factors (Baxter, 2009). Concentration and accumulation of elements is the result of many physiological processes, including root uptake, remobilisation and translocation within the plant, and subsequently deposition and storage in the seed (Shakoor et al, 2016)

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Discussion

Conclusion