Plant Reproduction最新文献

Key message: This review covers the latest developments on the regulation of early seed development by phytohormones. The development of seeds in flowering plants starts with the fertilization of the maternal gametes by two paternal sperm cells. This leads to the formation of two products, embryo and endosperm, which are surrounded by a tissue of maternal sporophytic origin, called the seed coat. The development of each of these structures is under tight genetic control. Moreover, several phytohormones have been shown to modulate the development of all three seed compartments and have been implicated in the communication between them. This is particularly relevant, as embryo, endosperm, and seed coat have to coordinate their development for successful seed formation. Here, we review the latest advances on the hormonal regulation of early seed development in the model plant species Arabidopsis thaliana, with a focus on the endosperm and the seed coat. Moreover, we highlight how phytohormones serve as mechanisms of non-cell autonomous communication between these two compartments and how they are determinant in shaping seed formation.

Key message: Candidate male sterility genes were identified in sugarcane, which interacts with kinase-related proteins, transcription factors, and plant hormone signaling pathways to regulate stamen and anther development. Saccharum officinarum is a cultivated sugarcane species that its predominant feature is high sucrose content in stems. Flowering is necessary for breeding new cultivars but will terminate plant growth and reduce sugar yield. The wild sugarcane species Saccharum spontaneum has robust and viable pollen, whereas most S. officinarum accessions are male sterile, which is a desirable trait of a maternal parent in sugarcane breeding. To study male sterility and related regulatory pathways in sugarcane, we carried out RNAseq using flowers in different developmental stages between male-sterile S. officinarum accession 'LA Purple' and fertile S. spontaneum accession 'SES208'. Gene expression profiles were used to detect how genes are differentially expressed between male sterile and fertile flowers and to identify candidate genes for male sterility. Weighted gene correlation networks analysis (WGCNA) was conducted to investigate the regulatory networks. Transcriptomic analyses showed that 988 genes and 2888 alleles were differentially expressed in S. officinarum compared to S. spontaneum. Ten differentially expressed genes and thirty alleles were identified as candidate genes and alleles for male sterility in sugarcane. The gene Sspon.03G0007630 and two alleles of the gene Sspon.08G0002270, Sspon.08G0002270-2B and Sspon.08G0014700-1A, were involved in the early stamen or carpel development stages, while the remaining genes were classified into the post-meiosis stage. Gibberellin, auxin, and jasmonic acid signaling pathways are involved in the stamen development in sugarcane. The results expanded our knowledge of male sterility-related genes in sugarcane and generated genomic resources to facilitate the selection of ideal maternal parents to improve breeding efficiency.

Key message: ARID-HMG DNA binding protein, AtHMGB15, regulates pollen development and pollen germination in Arabidopsis. Previous studies have shown that ARID-HMG DNA binding protein, AtHMGB15 regulate pollen development and pollen germination in Arabidopsis. Here, we performed transcriptome and cytological studies to understand the role of AtHMGB15 in regulating pollen wall morphology and the pollen tube germination rate. Our result showed abnormal vacuolization in the tapetal cells during anther maturation and prolonged PCD in AtHMGB15 loss-of-function mutant. The tapetum has the ability to perform both secretory and biosynthetic activities critical for pollen maturation and pollen viability. Interestingly, expression of PCD executer genes CEP1, MC9 and RNS3 were significant down-regulation of in athmgb15-4. The growth of pollen tubes is regulated by the actin cytoskeleton dynamics. To address the defect in pollen tube growth of athmgb15, we monitored the actin network in growing pollen tubes of wildtype and athmgb15-4 using Rhodamine-phalloidin fluorescence. Our results indicate a highly fragmented actin distribution in athmgb15-4 pollen tubes with a lesser number of long actin fibers and significantly low f-actin concentration at the apex. q-RTPCR further indicates significant downy-regulation of actin regulatory proteins VLN2 and PRF4. Collectively, our results suggest that AtHMGB15 being a nuclear architectural protein orchestrates high-order chromatin organization to promote the transcription of genes responsible for pollen development and pollen germination.

Key message: The DNA methylation status at an epigenetic quantitative trait locus in the Arabidopsis chromosome 2 is linked to the formation of apomictic-like endosperms. Seed development in most angiosperms is coupled to fertilization of the maternal gametes by two sperm cells. However, apomictic species can reproduce asexually via seeds. This trait is of great agricultural interest, as it would fix complex genotypes and allow for pollen-independent seed production. However, engineering full apomixis requires three independent processes: apomeiosis, parthenogenesis and autonomous endosperm development. While the first two have been successfully engineered in some crops, the formation of autonomous endosperms remains a challenge. Although it is known that this trait is under epigenetic control, such as of DNA methylation, the underlying mechanisms remain mostly undiscovered. Here, using epigenetic recombinant inbred lines, we identified an epigenetic quantitative trait locus in the Arabidopsis chromosome 2, which correlates with permissiveness for the formation of asexual seeds: hypomethylation at this genomic region allows the formation of larger autonomous endosperms. Importantly, the methylation at this locus only correlates with asexual seed size, and not to the size of sexual seeds or that of other organs. With this, we aim to show that screening for epialleles is a promising strategy to uncover loci underlying relevant traits and could pave the way to identifying genes necessary for the engineering of apomixis.

Key message: Different plant hormones contribute to maize reproductive success. Maize is a major crop species and significantly contributes directly and indirectly to human calorie uptake. Its success can be mainly attributed to its unisexual inflorescences, the tassel and the ear, whose formation is regulated by complex genetic and hormonal networks, and is influenced by environmental cues such as temperature, and nutrient and water availability. Traditional genetic analysis of classic developmental mutants, together with new molecular approaches, have shed light on many crucial aspects of maize reproductive development including the influence that phytohormones exert on key developmental steps leading to successful reproduction and seed yield. Here we will review both historical and recent findings concerning the main roles that phytohormones play in maize reproductive development, from the commitment to reproductive development to sexual reproduction.

Key message: Lipoxygenase activity and localization vary throughout the development of Larix kaempferi ovules, with the highest enzyme activity observed in ovules at the cellular stage and the most intense immunogold reaction noted at the mature archegonium stage of gametophyte development. Lipoxygenases are a family of oxidoreductases with a significant role in biological systems, widespread in living organisms e.g. mammals, fish, corals, plants, mosses, algae, fungi, yeasts, and bacteria. Lipoxygenase activity in plants leads to the formation of phytooxylipins, i.e. signaling molecules, which play a crucial role in many significant physiological processes such as male and female gametophyte maturation, germination and seedling growth, pathogen resistance, abiotic stress response, fruit ripening, and senescence. The activity and localization of lipoxygenase change during plant growth and development. The localization of lipoxygenase in a developing ovule of Larix kaempferi was analyzed using the immunogold labeling method, and the activity was determined spectrophotometrically with linolenic acid as a substrate. Among the investigated stages, the immunogold reaction was the most intense at the mature archegonium stage in the ovule. Lipoxygenase was found in all parts of the L. kaempferi ovule. The largest number of immunogold particles was detected in the integument cells of all the analyzed stages of ovule development. Only one isoform of lipoxygenase with an optimum at pH 8 was active in the ovules during female gametophyte maturation. The highest enzyme activity was determined at the cellular stage, whereas the mature archegonium stage was characterized by its lowest level, which means that LOX activity in developing ovules of the Japanese larch is not correlated with the number of antibody-labeled molecules of the enzyme.

Key message: This comprehensive review underscores the application of genome editing in plant reproductive biology, including recent advances and challenges associated with it. Genome editing (GE) is a powerful technology that has the potential to accelerate crop improvement by enabling efficient, precise, and rapid engineering of plant genomes. Over the last decade, this technology has rapidly evolved from the use of meganucleases (homing endonucleases), zinc-finger nucleases, transcription activator-like effector nucleases to the use of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (CRISPR/Cas), which has emerged as a popular GE tool in recent times and has been extensively used in several organisms, including plants. GE has been successfully employed in several crops to improve plant reproductive traits. Improving crop reproductive traits is essential for crop yields and securing the world's food supplies. In this review, we discuss the application of GE in various aspects of plant reproductive biology, including its potential application in haploid induction, apomixis, parthenocarpy, development of male sterile lines, and the regulation of self-incompatibility. We also discuss current challenges and future prospects of this technology for crop improvement, focusing on plant reproduction.

Key message: The formacion of numerous unpredictable DNA Double Strand Breaks (DSBs) on chromosomes iniciates meiotic recombination. In this perspective, we propose a 'multi-key lock' model to secure the risky but necesary breaks as well as a 'one per pair of cromatids' model for the topoisomerase-like early recombinosome. During meiosis, homologous chromosomes recombine at few sites of crossing-overs (COs) to ensure correct segregation. The initiation of meiotic recombination involves the formation of DNA double strand breaks (DSBs) during prophase I. Too many DSBs are dangerous for genome integrity: if these DSBs are not properly repaired, it could potentially lead to chromosomal fragmentation. Too few DSBs are also problematic: if the obligate CO cannot form between bivalents, catastrophic unequal segregation of univalents lead to the formation of sterile aneuploid spores. Research on the regulation of the formation of these necessary but risky DSBs has recently advanced in yeast, mammals and plants. DNA DSBs are created by the enzymatic activity of the early recombinosome, a topoisomerase-like complex containing SPO11. This opinion paper reviews recent insights on the regulation of the SPO11 cofactors necessary for the introduction of temporally and spatially controlled DSBs. We propose that a 'multi-key-lock' model for each subunit of the early recombinosome complex is required to secure the formation of DSBs. We also discuss the hypothetical implications that the established topoisomerase-like nature of the SPO11 core-complex can have in creating DSB in only one of the two replicated chromatids of early prophase I meiotic chromosomes. This hypothetical 'one per pair of chromatids' DSB formation model could optimize the faithful repair of the self-inflicted DSBs. Each DSB could use three potential intact homologous DNA sequences as repair template: one from the sister chromatid and the two others from the homologous chromosomes.

Key message: Total PME activity in reproductive tissues was related to haplotypes at maize cross incompatibility loci, suggesting that these loci function by controlling PME activity. In maize, the pollination outcome depends on the haplotypes of the interacting male gametophyte (germinated pollen) and female sporophyte (silk) at several cross-incompatibility loci. Functional alleles (-S haplotypes) of the cross-incompatibility loci Ga1 and Ga2, both encode two pectin methylesterases (PMEs), one that is expressed in silk and the other in pollen. We examined total PME activity in reproductive tissues containing functional and null haplotypes at the Ga1 or Ga2 loci. In pollinated silks, there was a correlation between total PME activity and the -S haplotype pollen in both Ga1 and Ga2 systems. We did not detect a significant relationship between PME activity and pollination outcome of either system. We re-examined previously reported active site amino acid substitutions in PMEs encoded by cross incompatibility loci. We observed that different active site substitutions are present in the pollen and silk PMEs of cross incompatibility loci and these differences are conserved across Ga1, Ga2 and Tcb-1. This work establishes a relationship between total PME activity and the haplotypes of the Ga1 locus in pollinated silks.

Key message: We describe transcriptional dynamics at the rice shoot apex by integrating time resolved single nuclei RNA-seq with bulk RNA-seq data. In rice, short days trigger floral transition and the transcriptional reprogramming of the shoot apex to become reproductive. We integrated time-resolved bulk RNA-seq with single nuclei RNA-seq analysis to gain a refined understanding of the transcriptional programs induced at the shoot apex during floral transition. Our analyses highlighted technological and conceptual differences between single nuclei RNA-seq and bulk RNA-seq data and described previously uncharacterized transcriptional programs associated with the early steps of floral induction in rice.