A genotype independent DMP-HI system in dicot crops

Abstract

Doubled haploid (DH) technology is used to obtain homozygous lines in a single generation, which significantly accelerates the crop breeding trajectory. Traditionally, in vitro culture is used to generate DHs, but is limited by species and genotype recalcitrance. In vivo haploid induction (HI) through seed is been widely and efficiently used in maize and was recently extended to several monocot crops. However, a similar generic and efficient HI system is still lacking in dicot crops. Here we show that genotype-independent in vivo HI can be triggered by mutation of DMP genes in tomato, rapeseed and tobacco with HI rates of ~1.9%, 2.4% and 1.2%, respectively. The DMP-HI system offers a robust DH technology to facilitate variety improvement in these crops. The success of this approach and the conservation of DMP genes paves the way for a generic and efficient genotype-independent HI system in other dicot crops.

BABY BOOM regulates early embryo and endosperm development

“…These expression patterns were reflected in novel BBM functions in endosperm and embryo development that were shared with PLT2. We also show that ectopic BBM expression in the egg cell induces parthenogenesis, a trait that can be enhanced by dmp maternal haploid inducers (18)(19)(20). Our findings consolidate previous research showing a role for BBM overexpression in embryo identity induction in somatic tissues with a similar role for BBM during zygotic embryogenesis, and uncover an unexpected role for BBM as a driver of endosperm development in plants.…”

“…After ploidy analysis, we noticed that many GFP-negative/putative haploid seedlings were true diploids, which might have been due to selection of seedlings with low RPS5A:AMV:GFP expression in the root tip. Given the low frequency of spontaneous haploid production in WT B. napus (0 out of 981 seedlings; SI Appendix, Table S7) (18,20,32), our data suggest that eggcell-expressed BBM also facilitates in vivo haploid embryo development in B. napus.…”

“…To evaluate whether an EC1:AMV:BBM × dmp cross can further increase the HIR in B. napus, three independent EC1:AMV: BBM transgenic lines, which showed haploid embryogenesis described above, were crossed with an available bndmp maternal haploid inducer line (20). Putative haploids were identified based on differential FAST-Red expression in the root and cotyledon as described previously (20). Ploidy analysis of these putative haploids suggested that haploid embryos developed at a similar rate in EC1:AMV:BBM × bndmp crosses and WT × bndmp crosses (SI Appendix, Table S8) (20).…”

“…Putative haploids were identified based on differential FAST-Red expression in the root and cotyledon as described previously (20). Ploidy analysis of these putative haploids suggested that haploid embryos developed at a similar rate in EC1:AMV:BBM × bndmp crosses and WT × bndmp crosses (SI Appendix, Table S8) (20).…”

“…We also examined BBM-induced haploid embryo induction in tomato (Solanum lycopersicon) seeds. In tomato, selfed seeds from four independent EC1:AMV:BBM transgenic lines were sown and putative haploids were identified based on their phenotype (smaller size and sterile) (20). Ploidy analysis of these putative haploids showed that haploid embryos developed in one of the four lines at a frequency of 1.4% (SI Appendix, Fig.…”