Genetic architecture of root and shoot ionomes in rice (Oryza sativa L.).

KEY MESSAGE: Association analysis for ionomic concentrations of 20 elements identified independent genetic factors underlying the root and shoot ionomes of rice, providing a platform for selecting and dissecting causal genetic variants. Understanding the genetic basis of mineral nutrient acquisition is key to fully describing how terrestrial organisms interact with the non-living environment. Rice (Oryza sativa L.) serves both as a model organism for genetic studies and as an important component of the global food system. Studies in rice ionomics have primarily focused on above ground tissues evaluated from field-grown plants. Here, we describe a comprehensive study of the genetic basis of the rice ionome in both roots and shoots of 6-week-old rice plants for 20 elements using a controlled hydroponics growth system. Building on the wealth of publicly available rice genomic resources, including a panel of 373 diverse rice lines, 4.8 M genome-wide single-nucleotide polymorphisms, single- and multi-marker analysis pipelines, an extensive tome of 321 candidate genes and legacy QTLs from across 15 years of rice genetics literature, we used genome-wide association analysis and biparental QTL analysis to identify 114 genomic regions associated with ionomic variation. The genetic basis for root and shoot ionomes was highly distinct; 78 loci were associated with roots and 36 loci with shoots, with no overlapping genomic regions for the same element across tissues. We further describe the distribution of phenotypic variation across haplotypes and identify candidate genes within highly significant regions associated with sulfur, manganese, cadmium, and molybdenum. Our analysis provides critical insight into the genetic basis of natural phenotypic variation for both root and shoot ionomes in rice and provides a comprehensive resource for dissecting and testing causal genetic variants.

Green tea ingestion by rats does not affect iron absorption but does alter the composition of the saliva proteome.

We tested the hypothesis that rats adapt to the iron absorption inhibitory effects of tea by modifying the expression of salivary proteins. Thirty-six weanling rats were allocated into 6 groups. Two control groups were fed a semipurified diet containing 20 mg Fe(2+)/kg diet. Two groups were fed spray dried green tea infusion mixed into the diet (28.6 g tea/kg diet) and 2 groups were fed the control diet with a twice daily gavage of a tea solution (0.25 g tea/mL). Saliva samples were collected in 3 groups (control, gavage, and oral) on day 8 (acute) and in the remaining groups on day 31 (chronic). Iron absorption was assessed using a (58)Fe(3+) tracer administered on day 1 (acute) and day 24 (chronic). 2D gel electrophoresis and mass spectrometry were used to assess the composition of the saliva proteome. There was no significant difference in iron absorption between the 3 groups on either day 1 or day 24. Salivary proline-rich proteins and submandibular gland secretory protein increased to a greater extent in the oral group than in the gavage group, when compared to control, within the same exposure time period. Amylase, chitinase, deoxyribonuclease, cysteine-rich secretory protein 1, and parotid secretory protein all decreased to a greater extent in the oral tea group, compared to the control, within the same exposure time period. Our results show that green tea did not decrease iron absorption in rats but it did have a marked effect on the saliva proteome when given orally.

Iron and zinc bioavailabilities to pigs from red and white beans (Phaseolus vulgaris L.) are similar.

Common beans contain relatively high concentrations of iron (Fe) and zinc (Zn) but are also high in polyphenols and phytates, factors that may inhibit Fe and Zn absorption. In vitro (Caco-2 cells) and in vivo (pigs) models were used to compare Fe and Zn bioavailabilities between red and white beans, which differ in polyphenol content. Bean/maize diets containing 37% of either white or red cooked beans were formulated. Fe uptake by Caco-2 cells was 14-fold higher from the white bean diet compared to the red bean diet. The diets were fed to anemic piglets (n = 10) for 35 days. On experiment days 7 and 21, pigs were given meals containing beans intrinsically labeled with stable isotopes of Fe and Zn ((58)Fe, (70)Zn), followed by intravenous (iv) injections of (54)Fe and (67)Zn, to assess Fe and Zn absorption. Isotope ratios determined by inductively coupled plasma mass spectrometry in whole blood and plasma samples were used to calculate iron and zinc absorption, respectively. On day 35, animals were killed and duodenal sections were collected for DMT1 gene expression analysis. Fe absorption was 14 and 16% from the first labeled meal and 9 and 10.5% from the second labeled meal for the white and red beans, respectively (P > 0.05). Zn absorption was 28 and 23% from the first meal (P > 0.05) and 31 and 29% from the second meal (P > 0.05) for the white and red beans, respectively. DMT1 gene expression did not differ between treatments. It was concluded that bean color does not affect Fe or Zn bioavailability in vivo and that beans are a good source of bioavailable Fe and Zn.