Dissertations, Theses, and Capstone Projects

Date of Degree

9-2021

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Renuka Sankaran

Committee Members

Edward Kennelly

Michael Grusak

Ruth Stark

Brian Waters

Subject Categories

Agriculture | Biology | Food Science | Laboratory and Basic Science Research | Molecular Biology

Keywords

Rice, Cadmium, Zinc, Bioaccessibility

Abstract

The effect of cadmium and zinc on mineral concentrations in three cultivars of rice

Interactions between the essential mineral zinc (Zn) and the toxic heavy metal cadmium (Cd) play an important role in regulating transport of both minerals to rice grains. Understanding these interactions is crucial for limiting cadmium and increasing zinc transfer to the food chain. Previous studies on the matter have had conflicting results suggesting synergistic and antagonistic relationships between the minerals. The goal of this work was to identify the effect of external cadmium and zinc on the uptake and translocation of both minerals from roots to grains of rice that differ in grain cadmium concentrations. Our results suggest zinc affects cadmium translocation and accumulation to the grain while cadmium does not have an effect on zinc. Cadmium synergy or antagonism with other essential minerals were also recorded and differed between rice lines. Differential expression of established transport proteins OsNramp5, OsHMA2, and OsHMA3, play a vital role in contributing to differences in grain cadmium. These results add to the knowledge of cadmium and zinc transport in one of the most consumed plant foods in the world and can assist fortification efforts to establish rice lines that are both safe and nutritious.

The effect of exogenous cadmium and zinc applications on cadmium, zinc, and essential mineral bioaccessibility in three lines of rice that differ in grain cadmium concentration

Diets high in cadmium (Cd) and low in zinc (Zn) threaten human health. While both are detrimental to the well-being of millions globally, diets affected by both simultaneously are especially dangerous as the impacts are exaggerated. Rice is particularly adept at accumulating high concentrations of cadmium and low concentrations of zinc in grains. Several strategies to limit cadmium and increase zinc from rice grain have been explored but total mineral concentration in rice grain is an unreliable means of estimating human health risk since only a fraction of the minerals in grains are bioaccessible. The goal of this work was to assess the influence of phytoavailable cadmium and zinc on the bioaccessibility of essential minerals and cadmium from three rice lines that differed in grain cadmium accumulation. Results revealed that exogenous Cd and Zn both increased the BA of the other mineral in the low or high Cd concentration varieties of rice. Differences in mineral bioaccessibility were dependent on rice line. This information can be helpful to future experiments to analyze genotypic effects of mineral bioavailability from rice.

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