Biology subjects

Marques, J. P. R.

Publications and source records attributed to Marques, J. P. R..

4 recordsLinked to original sources

bioRxiv2025

Double knockout of rice OsVIT1 and OsVIT2 genes reveals a trade-off between iron biofortification and iron excess tolerance

Rice (Oryza sativa L.) is a staple food for half of the worlds population, but lacks essential nutrients such as iron (Fe). Fe deficiency is one of the most common nutritional problems in humans, and biofortification of rice grains is a cost-effective approach to deliver more Fe to peoples diet. Two Vacuolar Iron Transporters, OsVIT1 and OsVIT2, were shown to negatively regulate Fe translocation to rice developing panicles, as single mutants osvit1 and osvit2 have increased Fe concentration in seeds. Importantly, rice plants are frequently cultivated in waterlogged soils that are highly reductive and prone to Fe3+ reduction to the more soluble Fe2+, which can accumulate and cause Fe toxicity. Little is known about which genes control Fe excess detoxification. OsVIT1 and OsVIT2 transport Fe into the vacuole, and OsVIT2 is induced under Fe excess, but whether they play a role in Fe detoxification was not demonstrated. We generated double mutants osvit1osvit2 using CRISPR-Cas9 to test whether loss of function of both genes could increase Fe concentration in seeds, and to test whether their loss of function has impact in rice Fe excess tolerance. We showed that osvit1osvit2 double mutants accumulated more Fe in brown rice. Fe accumulation was clear in embryo scutellum and plumule, suggesting VIT transporters have a role in determining Fe spatial distribution. We also showed that root uptake contributed significantly for increased Fe accumulation in osvit1osvit2 seeds, suggesting OsVIT1 and OsVIT2 are involved in sequestering Fe in vegetative tissues and decreasing translocation. Strikingly, we found that osvit1osvit2 plants were more sensitive to Fe excess, revealing a trade-off between Fe biofortification and Fe excess tolerance. Our data indicates OsVIT1 and OsVIT2 are key for Fe excess detoxification, which should be considered in their use as targets for biofortification.

plant biology↗

bioRxiv2025

Storage protein biosynthesis is affected by ionome composition in soybean (Glycine max (L.) Merrill) seeds

Soybean seeds are a significant source of protein for human and animal nutrition, primarily due to seed storage proteins (SSPs) from the albumin and globulin families, which are predominantly located in protein storage vacuoles within cotyledon cells. This study characterised the dynamics of protein and mineral nutrient accumulation in four soybean genotypes with contrasting protein content--two transgenic (tg1 and tg2) and two conventional (ct1 and ct2)--from the beginning of seed filling (R5.5) through to maturity (R8) under field conditions. Profiles of globulin SSPs (glycinin and {beta}-conglycinin), as well as the protein and elemental distribution in mature seed cotyledons were examined. Results revealed that genotypes with higher protein content showed increased S and Zn concentrations and a higher glycinin:{beta}-conglycinin ratio. Subcellular analyses further indicated co-localisation of proteins and Zn within cotyledon cells. Our findings reveal a complex association between S and Zn accumulation and SSPs biosynthesis, indicating that their availability can limit the SSP content. HIGHLIGHTSoybean seed genotypes containing higher sulphur (S) and zinc (Zn) content in the cotyledonary cells exhibit a distinct storage proteins profile by increasing the abundance of sulphur-amino acids rich globulins.

plant biology↗

bioRxiv2022

Microprobe-XRF assessment of nutrient distribution in soybean, cowpea, and kidney bean seeds: a Fabaceae family case study

The present study explored the microprobe X-ray fluorescence spectroscopy ({micro}-XRF) for quantitative and space-resolved distribution of macro, i.e., K, P, S, and Ca, and micronutrients, i.e., Fe, Zn, and Mn elemental composition in the cross-sectioned seeds of cowpea (Vigna unguiculata L.), kidney bean (Phaseolus vulgaris L.), and soybean (Glycine max L.) seeds, important agricultural species within the Fabaceae family. It unveils that both macro and micronutrients were heterogeneously distributed across seed tissues. Most of the P and S, Fe, Zn, and Mn were mainly found at the embryo axis tissues in all three Fabaceae species, whereas K was spread along the cotyledon and Ca was mostly observed trapped at the seed coat region. Furthermore, the Pearson correlation coefficient revealed a strong spatial correlation between P and S, and K and S in cowpea and soybean seed tissues, whereas Zn and Mn association was also recorded. Therefore, the {micro}-XRF technique demonstrates to be an important tool for assessing seed nutrient distribution, thus subsidizing the understanding of the physiological role of nutrients in seeds and fostering innovative approaches for nutrient supply and biofortification.

biochemistry↗

bioRxiv2022

Physiological responses of plants to in vivo XRF radiation damage: insights from elemental, histochemical, anatomical and ultrastructural analyses

X-ray fluorescence spectroscopy (XRF) is a powerful technique for the in vivo assessment of plant tissues. However, the potential X-ray exposure damages might affect the structure and elemental composition of living plant tissues leading to artefacts in the recorded data. Herein, we exposed soybean (Glycine max (L.) Merrill) leaves to several X-ray doses through a polychromatic benchtop microprobe X-ray fluorescence spectrometer, modulating the photon flux by adjusting either the beam size, focus, or exposure time. The structure, ultrastructure and physiological responses of the irradiated plant tissues were investigated through light and transmission electron microscopy (TEM). Depending on the dose, the X-ray exposure induced decreased K and X-ray scattering intensities, and increased Ca, P, and Mn signals on soybean leaves. Anatomical analysis indicated necrosis of the epidermal and mesophyll cells on the irradiated spots, where TEM images revealed the collapse of cytoplasm and cell-wall breaking. Furthermore, the histochemical analysis detected the production of reactive oxygen species, as well as inhibition of chlorophyll autofluorescence in these areas. Under certain X-ray exposure conditions, e.g., high photon flux and exposure time, XRF measurements may affect the soybean leaves structures, elemental composition, and cellular ultrastructure, and induce programmed cell death. These results shed light on the characterization of the radiation damage, and thus, help to assess the X-ray radiation limits and strategies for in vivo for XRF analysis. HighlightBy exposing soybean leaves to several X-ray doses, we show that the characteristic X-ray induced elemental changes stem from plants physiological signalling or responses rather than only sample dehydration.

plant biology↗