Understanding and exploiting uniparental genome elimination in plants: insights from Arabidopsis thaliana

Abstract

Vacuolar storage of iron (Fe) is important for Fe homeostasis in plants. When sufficient, the excess Fe could be stored in vacuoles for remobilization in case of Fe deficiency. Although the mechanism of Fe remobilization from vacuoles is critical for crop development under low Fe stress, the transporters that mediate vacuolar Fe translocation into the cytosol in rice remains unknown. Here, we showed that under higher Fe 2+ concentrations, the Δccc1 yeast mutant transformed with rice natural resistance-associated macrophage protein 2 (OsNRAMP2) became more sensitive to Fe toxicity. In rice protoplasts and transgenic plants expressing Pro35S: OsNRAMP2-GFP, OsNRAMP2 was localized to tonoplast. Vacuolar Fe contents in osnramp2 knockdown lines were higher than in the wild-type, while the growth of osnramp2 knockdown plants was significantly influenced by Fe deficiency. Furthermore, the germination of osnramp2 knockdown plants was arrested. Inversely, the vacuolar Fe contents of Pro35S: OsNRAMP2-GFP lines were significantly lower than in the wild-type, and overexpression of OsNRAMP2 increased shoot biomass under Fe deficiency. Taken together, we propose that OsNRAMP2 transports Fe from the vacuole to the cytosol and plays a pivotal role in seed germination.

High temperature increases centromere-mediated genome elimination frequency and enhances haploid induction in Arabidopsis

“…Originally, it was thought that haploids could be obtained only by crossing cenh3 mutant lines complemented by a modified version of cenH3 with the wild-type ( Ravi et al., 2014 ; Thondehaalmath et al., 2021 ). To understand the mechanism of genome elimination in such crosses, Marimuthu et al.…”

High temperature increases centromere-mediated genome elimination frequency in Arabidopsis deficient in cenH3 or its assembly factor KNL2

“…This indicates that the haploid induction in centromere impaired mutants is conditioned by temperature stress during both ovule development as well as early embryogenesis. Originally, it was thought that haploids could only be obtained by crossing the cenh3 mutant lines complemented by a modified version of cenH3 with the wild-type, as the elimination of one of the genomes is caused by competition between two structurally different cenH3 variants for the deposition to centromeres (Ravi et al ., 2014, Thondehaalmath et al ., 2021). To understand the mechanism of genome elimination in such crosses, Marimuthu et al .…”

“…Originally, it was thought that haploids could only be obtained by crossing the cenh3 mutant lines complemented by a modified version of cenH3 with the wild-type, as the elimination of one of the genomes is caused by competition between two structurally different cenH3 variants for the deposition to centromeres (Ravi et al, 2014, Thondehaalmath et al, 2021. To understand the mechanism of genome elimination in such crosses, Marimuthu et al (2021) analyzed the distribution of the altered cenH3 (GFP-tail swap) variant in gametes and at different developmental stages of hybrid zygotes.…”

Doubled Haploids in Eggplant

“…In the last decade, the manipulation of certain genes has allowed for the production of haploid inducer lines in different species. In maize, mutations in genes like NOT LIKE DAD (NLD)/MATRILINEAL (MATL)/patatinlike phospholipase-A1 (PLA1) or DOMAIN OF UNKNOWN FUNCTION 679 (DMP) have consistently generated lines that, when crossed with elite materials, produce haploids with the genome of the elite line [76,77]. Unfortunately, NLD/MATL/ZmPLA1 does not have homologs in dicots, but the dicot Arabidopsis thaliana has multiple DMP-like homologs, and one of the double mutants generated (atdmp8-/-atdmp9-/-) was shown to induce haploids when crossed [78].…”