Influence of seed priming with iron and/or zinc in the nucleolar activity and protein content of bread wheat
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Seed priming with iron (Fe) and/or zinc (Zn) can overcome the reduced availability of these micronutrients in soils and crops, but suitable dosages should be predetermined. Nucleolus responds to stress, such as cytotoxicity, with alterations perceivable by cytogenetic analyses. This work intends to study how seed priming with Fe and/or Zn affects the nucleolar activity in roots and the total soluble protein content in the flour of bread wheat cv. ‘Jordão’. Seven priming treatments with 0 mg L−1 to 8 mg L−1 of Fe and/or Zn were performed. In all treatments, each metaphase cell presented a maximum of six nucleolar organizer regions positively stained with silver nitrate (Ag-NORs). Also, a maximum number of six nucleoli per nucleus were observed in all treatments, except in the hydroprimed seeds (used as control) that showed a maximum of five nucleoli, probably due to nucleolar fusion. Irregular interphases were frequent in treatments with the highest dosage of micronutrients (8 mg L−1 Fe and/or 8 mg L−1 Zn). The nucleolar area reduced (p < 0.001) as the number of nucleoli increased, and it was lower in treatments with a combination of Fe and Zn. However, the combinations of Fe and Zn showed the highest concentrations of total soluble protein (p ≤ 0.001). Although a reduced nucleolar area represents low ribosomal RNA gene transcription and ribosomal production, the significant increase of the number of nucleoli in the seeds primed with Fe and Zn enhanced the total soluble protein content as compared to the hydroprimed seeds (control) probably due to an increase of nucleolar surface-to-volume ratio that improved the protein synthesis. Overall, this work revealed that priming of bread wheat seeds with suited dosages of Fe and Zn can improve the nutritional value of flour, and the nucleolar number, morphology, and area can be useful biomarkers in cytotoxicity studies.
KeywordsMicronutrients Nucleolar area Nucleoli Salt-nylon silver nitrate staining Total soluble protein Triticum aestivum L. em. Thell.
The authors thank Eng. Coutinho from the INIAV (Elvas) for kindly providing the seeds of the bread wheat cultivar ‘Jordão’. The authors A.C. and J.L.-B. acknowledge the projects UID/MULTI/04046/2013 and UID/AGR/04033/2013 (supported by the FCT - Portuguese Foundation for the Science and Technology) and POCI-01-0145-FEDER-006958 (supported by FEDER/COMPETE/POCI – Operational Competitiveness and Internationalization Programme) and the COST ACTION CA16212, “INDEPTH” - “Impact of nuclear domains on gene expression and plant traits” (European Cooperation in Science and Technology).
This work was supported by the “Fundação para a Ciência e a Tecnologia” (FCT) (grant number PD/BD/113611/2015) attributed to author I.P. in the scope of the Ph.D. program “Agricultural production chains—from fork to farm” (PD/00122/2012).
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Conflict of interest
The authors declare that they have no conflict of interest.
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