A female in vivo haploid-induction system via mutagenesis of egg cell-specific peptidases

Do egg cell‐secreted aspartic proteases promote gamete attachment?

“…Moreover, we found that ECS1/2 also regulates male and female nuclear fusion in the fertilized egg cell. As a consequence, partially semigamous zygotes and haploid offspring were generated (Zhang et al, 2023). More recently, Jiang et al (2022) confirmed the critical role of ECS1/2 in plant fertility and discussed that the endopeptidases are also involved in gamete interaction.…”

Response to Zhang et al., ‘do egg cell‐secreted aspartic proteases promote gamete attachment?’

“…Both Mao et al (2022) and we (Jiang et al, 2022) observed central cell single‐fertilized ovules, in which the egg cell was unfertilized, and these ovules eventually developed into aborted seeds. Meanwhile, both Zhang et al (2023b) and we (Jiang et al, 2022) observed embryogenesis defect in the ecs1 ecs2 double mutants, despite a slight difference in the ratio. We suspect that these phenotypic discrepancies are possibly attributed to the different mutation forms of the mutants.…”

“…One thing that needs to be noted is that the observed defect phenotypes and the ratio of the defects reported in the three papers are somehow slightly different (Jiang et al, 2022; Mao et al, 2022; Zhang et al, 2023b [BioRxiv, 476184 (2022)]). Both Mao et al (2022) and we (Jiang et al, 2022) observed central cell single‐fertilized ovules, in which the egg cell was unfertilized, and these ovules eventually developed into aborted seeds.…”

The Roads to Haploid Embryogenesis

“…EGG CELL-SPECIFIC1/2 ( ECS1 /2) encodes egg cell-specifically expressed aspartic proteases, which are secreted to the synergid cell region upon fertilization to avoid polytubey by degrading the pollen tube attractant LURE1 [ 75 ]. Recently, two independent studies demonstrated that the mutation of ECS1 and ECS2 can also induce haploid embryogenesis [ 76 , 77 ]. Unfused sperm nuclei were observed in zygotes and early embryos, suggesting that karyogamy defects occurred in the sperm–egg fertilization, and the haploids from the ecs1 ecs2 mutant progenies may have resulted from the post-fertilization genomic elimination [ 77 ].…”

“…Recently, two independent studies demonstrated that the mutation of ECS1 and ECS2 can also induce haploid embryogenesis [ 76 , 77 ]. Unfused sperm nuclei were observed in zygotes and early embryos, suggesting that karyogamy defects occurred in the sperm–egg fertilization, and the haploids from the ecs1 ecs2 mutant progenies may have resulted from the post-fertilization genomic elimination [ 77 ]. In summary, ECS -mediated haploid induction is likely caused by pseudogamy and potential post-fertilization genomic elimination ( Figure 2 d).…”