The cytoplasm of Aegilops kotschyi is known for the induction of male sterility and haploidy in wheat. Both systems originally appeared rather simple, but manipulation of the standard chromosome constitution of the nuclear genome revealed additional interactions. This study shows that while there is little or no allelic variation at the main fertility restorer locus Rfmulti on chromosome arm 1BS, additional genes may also be involved in the nuclear-mitochondrial genome interactions, affecting not only male fertility but also the growth rate, from pollen competition for fertilization and early endosperm divisions all the way to seed size and plant maturity. Some of these effects appear to be of a sporophytic nature; others are gametophytic. Induction of parthenogenesis by a rye inducer in conjunction with the Ae. kotschyi cytoplasm is well known. However, here we show that the cytoplasmic-nuclear interactions affect all aspects of double fertilization: producing maternal haploids from unfertilized eggs, diploids from fertilized eggs or synergids, embryo-less kernels, and fertilized eggs without fertilization of the double nucleus in the embryo sack. It is unclear how frequent the inducers of parthenogenesis are, as variation, if any, is obscured by suppressors present in the wheat genome. Genetic dissection of a single wheat accession revealed five distinct loci affecting the rate of maternal haploid production: four acting as suppressors and one as an enhancer. Only when the suppressing haplotypes are confirmed may it be possible to the identify genetic variation of haploidy inducers, map their position(s), and determine their nature and the mode of action.

CONCLUSIONS: The exploration and dissection of a set of QTLs and candidate genes for gray leaf spot disease resistance using two fully assembled parental genomes may help expedite maize resistance breeding. The fungal disease of maize known as gray leaf spot (GLS), caused by Cercospora zeae-maydis and Cercospora zeina, is a significant concern in China, Southern Africa, and the USA. Resistance to GLS is governed by multiple genes with an additive effect and is influenced by both genotype and environment. The most effective way to reduce the cost of production is to develop resistant hybrids. In this study, we utilized the IBM Syn 10 Doubled Haploid (IBM Syn10 DH) population to identify quantitative trait loci (QTLs) associated with resistance to gray leaf spot (GLS) in multiple locations. Analysis of seven distinct environments revealed a total of 58 QTLs, 49 of which formed 12 discrete clusters distributed across chromosomes 1, 2, 3, 4, 8 and 10. By comparing these findings with published research, we identified colocalized QTLs or GWAS loci within eleven clustering intervals. By integrating transcriptome data with genomic structural variations between parental individuals, we identified a total of 110 genes that exhibit both robust disparities in gene expression and structural alterations. Further analysis revealed 19 potential candidate genes encoding conserved resistance gene domains, including putative leucine-rich repeat receptors, NLP transcription factors, fucosyltransferases, and putative xyloglucan galactosyltransferases. Our results provide a valuable resource and linked loci for GLS marker resistance selection breeding in maize.

Doubled haploid (DH) technology and synthetic apomixis approaches can considerably shorten breeding cycles and enhance breeding efficiency. Compared with traditional breeding methods, DH technology offers the advantage of rapidly generating inbred lines, while synthetic apomixis can effectively fix hybrid vigor. In this review, we focus on (i) recent advances in identifying and characterizing genes responsible for haploid induction (HI), (ii) the molecular mechanisms of HI, (iii) spontaneous haploid genome doubling, and (iv) crop synthetic apomixis. We also discuss the challenges and potential solutions for future crop breeding programs utilizing DH technology and synthetic apomixis. Finally, we provide our perspectives about how to integrate DH and synthetic apomixis for precision breeding and de novo domestication.

Increasing planting density is a key strategy for enhancing maize yields1-3. An ideotype for dense planting requires a \'smart canopy\' with leaf angles at different canopy layers differentially optimized to maximize light interception and photosynthesis4-6, among other features. Here we identified leaf angle architecture of smart canopy 1 (lac1), a natural mutant with upright upper leaves, less erect middle leaves and relatively flat lower leaves. lac1 has improved photosynthetic capacity and attenuated responses to shade under dense planting. lac1 encodes a brassinosteroid C-22 hydroxylase that predominantly regulates upper leaf angle. Phytochrome A photoreceptors accumulate in shade and interact with the transcription factor RAVL1 to promote its degradation via the 26S proteasome, thereby inhibiting activation of lac1 by RAVL1 and decreasing brassinosteroid levels. This ultimately decreases upper leaf angle in dense fields. Large-scale field trials demonstrate that lac1 boosts maize yields under high planting densities. To quickly introduce lac1 into breeding germplasm, we transformed a haploid inducer and recovered homozygous lac1 edits from 20 diverse inbred lines. The tested doubled haploids uniformly acquired smart-canopy-like plant architecture. We provide an important target and an accelerated strategy for developing high-density-tolerant cultivars, with lac1 serving as a genetic chassis for further engineering of a smart canopy in maize.

CONCLUSIONS: Stable and novel QTLs that affect seed vigor under different storage durations were discovered, and BnaOLE4, located in the interval of cqSW-C2-3, increased seed vigor after aging. Seed vigor is an important trait in crop breeding; however, the underlying molecular regulatory mechanisms governing this trait in rapeseed remain largely unknown. In the present study, vigor-related traits were analyzed in seeds from a doubled haploid (DH) rapeseed (Brassica napus) population grown in 2 different environments using seeds stored for 7, 5, and 3 years under natural storage conditions. A total of 229 quantitative trait loci (QTLs) were identified and were found to explain 3.78%-17.22% of the phenotypic variance for seed vigor-related traits after aging. We further demonstrated that seed vigor-related traits were positively correlated with oil content (OC) but negatively correlated with unsaturated fatty acids (FAs). Some pleiotropic QTLs that collectively regulate OC, FAs, and seed vigor, such as uq.A8, uq.A3-2, uq.A9-2, and uq.C3-1, were identified. The transcriptomic results from extreme pools of DH lines with distinct seed vigor phenotypes during accelerated aging revealed that various biological pathways and metabolic processes (such as glutathione metabolism and reactive oxygen species) were involved in seed vigor. Through integration of QTL analysis and RNA-Seq, a regulatory network for the control of seed vigor was constructed. Importantly, a candidate (BnaOLE4) from cqSW-C2-3 was selected for functional analysis, and transgenic lines overexpressing BnaOLE4 showed increased seed vigor after artificial aging. Collectively, these results provide novel information on QTL and potential candidate genes for molecular breeding for improved seed storability.

Neurological diseases are expected to become the leading cause of death in the next decade. Although little is known about it, the interaction between oxidative stress and inflammation is harmful to the nervous system. To find an advanced tool for neural genetics, mouse haploid neural stem cells (haNSCs) from the somite of chimeric mouse embryos at E8.5 is established. The haNSCs present a haploid neural progenitor identity for long-term culture, promising to robustly differentiate into neural subtypes and being able to form cerebral organoids efficiently. Thereafter, haNSC mutants via a high-throughput approach and screened targets of oxidative stress is generated using the specific mutant library. Deletion of Nfkbia (the top hit among the insertion mutants) reduces damage from reactive oxygen species (ROS) in NSCs exposed to H2O2. Transcriptome analysis revealed that Atp2b4 is upregulated significantly in Nfkbia-null NSCs and is probably responsible for the observed resistance. Additionally, overexpression of Atp2b4 itself can increase the survival of NSCs in the presence of H2O2, suggesting that Atp2b4 is closely involved in this resistance. Herein, a powerful haploid system is presented to study functional genetics in neural lineages, shedding light on the screening of critical genes and drugs for neurological diseases.

Bacterial blight, a major disease in rice, poses a serious impact on rice production. In this study, a doubled haploid (DH) population derived from a cross between the introduced japonica cultivar \'Maybelle\' and the indica landrace \'Baiyeqiu\' was used to investigate the pathogenicity of four pathogen races causing bacterial blight. The results showed that the pathogenicity of all the pathogen races exhibited continuous, transgressive distribution in the DH population. Moreover, strong correlations existed between every two pathogen races, with the correlation coefficients ranging from 0.3 to 0.6. A total of 12 quantitative trait loci (QTLs) distributed on chromosomes 1, 2, 3, 5, 6, 7, 9, and 12 were detected for rice bacterial blight, explaining 4.95% to 16.05% of the phenotype. Among these QTLs, a major QTL located in the interval RM6024-RM163 on chromosome 5 was detected in three pathogen races. In addition, the pyramiding of the positive alleles can apparently improve the rice resistance to bacterial blight. This study is of great significance for broadening the genetic resources with resistance to bacterial blight in China.

Haploid cells are a kind of cells with only one set of chromosomes. Compared with traditional diploid cells, haploid cells have unique advantages in gene screening and drug-targeted therapy, due to their phenotype being equal to the genotype. Embryonic stem cells are a kind of cells with strong differentiation potential that can differentiate into various types of cells under specific conditions in vitro. Therefore, haploid embryonic stem cells have the characteristics of both haploid cells and embryonic stem cells, which makes them have significant advantages in many aspects, such as reproductive developmental mechanism research, genetic screening, and drug-targeted therapy. Consequently, establishing haploid embryonic stem cell lines is of great significance. This paper reviews the progress of haploid embryonic stem cell research and briefly discusses the applications of haploid embryonic stem cells.

Ethylene (ET) is an important phytohormone that regulates plant growth, development and stress responses. The ethylene-insensitive3/ethylene-insensitive3-like (EIN3/EIL) transcription factor family, as a key regulator of the ET signal transduction pathway, plays an important role in regulating the expression of ET-responsive genes. Although studies of EIN3/EIL family members have been completed in many species, their role in doubled haploid (DH) poplar derived from another culture of diploid Populus simonii × P. nigra (donor tree, DT) remains ambiguous. In this study, a total of seven EIN3/EIL gene family members in the DH poplar genome were identified. Basic physical and chemical property analyses of these genes were performed, and these proteins were predicted to be localized to the nucleus. According to the phylogenetic relationship, EIN3/EIL genes were divided into two groups, and the genes in the same group had a similar gene structure and conserved motifs. The expression patterns of EIN3/EIL genes in the apical buds of different DH poplar plants were analyzed based on transcriptome data. At the same time, the expression patterns of PsnEIL1, PsnEIN3, PsnEIL4 and PsnEIL5 genes in different tissues of different DH plants were detected via RT-qPCR, including the apical buds, young leaves, functional leaves, xylem, cambium and roots. The findings presented above indicate notable variations in the expression levels of PsnEIL genes across various tissues of distinct DH plants. Finally, the PsnEIL1 gene was overexpressed in DT, and the transgenic plants showed a dwarf phenotype, indicating that the PsnEIL1 gene was involved in regulating the growth and development of poplar. In this study, the EIN3/EIL gene family of DH poplar was analyzed and functionally characterized, which provides a theoretical basis for the future exploration of the EIN3/EIL gene function.

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