Biology subjects

Frei, M.

Publications and source records attributed to Frei, M..

3 recordsLinked to original sources

bioRxiv2020

Introgression from Oryza meridionalis into domesticated rice Oryza sativa results in shoot-based iron tolerance

Iron (Fe) toxicity is one of the most common mineral disorders affecting rice (Oryza sativa) production in flooded lowland fields. Oryza meridionalis is endemic from Northern Australia and grows in regions with Fe rich soils, making it a candidate for use in adaptive breeding. Aiming to understand tolerance mechanisms in rice, we screened a population of interspecific introgression lines (IL) from a cross between O. sativa and O. meridionalis for the identification of QTLs contributing to Fe toxicity tolerance. Six putative QTLs were identified. A line carrying one introgression from O. meridionalis on chromosome 9 associated with one QTL was highly tolerant despite very high shoot Fe concentrations. Physiological, biochemical, ionomic and transcriptomic analyses showed that the IL tolerance could partly be explained by Fe retention in the leaf sheath and culm. We constructed the interspecific hybrid genome in silico for transcriptomic analysis, and identified differentially regulated introgressed genes from O. meridionalis that could be involved in shoot-based Fe tolerance, such as metallothioneins, glutathione S-transferases and transporters from ABC and MFS families. This is the first work to demonstrate that introgressions of O. meridionalis into the O. sativa genome can confer increased tolerance to excess Fe. HighlightWe identified QTLs associated with iron tolerance derived from O. meridionalis, and characterized their physiological basis in O. sativa.

plant biology↗

bioRxiv2020

ITPK1 is an InsP6/ADP phosphotransferase that controls systemic phosphate homeostasis in Arabidopsis

In plants, phosphate (Pi) homeostasis is regulated by the interaction of Pi starvation response transcription factors (PHRs) with stand-alone SPX proteins, which act as sensors for inositol pyrophosphates (PP-InsPs). Recently, ITPK1 was shown to generate the PP-InsP InsP7 from InsP6 in vitro, but the importance of this activity in Pi signaling remained unknown. Here, we show that uncontrolled Pi accumulation in ITPK1-deficient plants is accompanied by impaired Pi-dependent InsP7 and InsP8 synthesis. Reciprocal grafting demonstrates that Pi starvation responses are mainly controlled by ITPK1 activity in shoots. Nuclear magnetic resonance assays and PAGE analyses with recombinant protein reveal that besides InsP6 phosphorylation, ITPK1 is also able to catalyze ATP synthesis using 5-InsP7 but not any other InsP7 isomer as a P-donor when ATP is low. Additionally, we show that the dynamic changes in InsP7 and InsP8 to cellular Pi are conserved from land plant species to human cells, suggesting that Pi-dependent PP-InsP synthesis is a common component of Pi signaling across kingdoms. Together, our study demonstrates how Pi-dependent changes in nutritional and energetic states modulate ITPK1 activities to fine-tune the synthesis of PP-InsPs.

plant biology↗

bioRxiv2019

Evaluation of rice wild relatives as a source of traits for adaptation to iron toxicity and enhanced grain quality

Rice wild relatives (RWR) constitute an extended gene pool that can be tapped for the breeding of novel rice varieties adapted to abiotic stresses such as iron (Fe) toxicity. Therefore, we screened 75 Oryza genotypes including 16 domesticated O. sativas, one O. glaberrima, and 58 RWR representing 21 species, for tolerance to Fe toxicity. Plants were grown in a semi-artificial greenhouse setup, in which they were exposed either to control conditions, an Fe shock during the vegetative growth stage (acute treatment), or to a continuous moderately high Fe level (chronic treatment). In both stress treatments, foliar Fe concentrations were characteristic of Fe toxicity, and plants developed foliar stress symptoms, which were more pronounced in the chronic Fe stress especially toward the end of the growing season. Among the genotypes that produced seeds, only the chronic stress treatment significantly reduced yields due to increases in spikelet sterility. Moreover, a moderate but non-significant increase in grain Fe concentrations, and a significant increase in grain Zn concentrations were seen in chronic stress. Both domesticated rice and RWR exhibited substantial genotypic variation in their responses to Fe toxicity. Although no RWR strikingly outperformed domesticated rice in Fe toxic conditions, some genotypes scored highly in individual traits. Two O. meridionalis accessions were best in avoiding foliar symptom formation in acute Fe stress, while an O. rufipogon accession produced the highest grain yields in both chronic and acute Fe stress. In conclusion, this study provides the basis for using interspecific crosses for adapting rice to Fe toxicity.

plant biology↗