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Ovules contain the female gametophytes which are fertilized during pollination to initiate seed development. Thus, the number of ovules that are produced during flower development is an important determinant of seed crop yield and plant fitness. Mutants with pleiotropic effects on development often alter the number of ovules, but specific regulators of ovule number have been difficult to identify in traditional mutant screens. We used natural variation in Arabidopsis accessions to identify new genes involved in the regulation of ovule number. The ovule numbers per flower of 189 Arabidopsis accessions were determined and found to have broad phenotypic variation that ranged from 39 ovules to 84 ovules per pistil. Genome-Wide Association tests revealed several genomic regions that are associated with ovule number. T-DNA insertion lines in candidate genes from the most significantly associated loci were screened for ovule number phenotypes. The NEW ENHANCER of ROOT DWARFISM (NERD1) gene was found to have pleiotropic effects on plant fertility that include regulation of ovule number and both male and female gametophyte development. Overexpression of NERD1 increased ovule number per fruit in a background-dependent manner and more than doubled the total number of flowers produced in all backgrounds tested, indicating that manipulation of NERD1 levels can be used to increase plant productivity.

Reactive oxygen species (ROS) are toxic by-products of aerobic metabolism. In plants, they also function as important signaling molecules that regulate biotic and abiotic stress responses as well as plant growth and development. Recent studies have implicated ROS in various aspects of plant reproduction. In male gametophytes, ROS are associated with germline development as well as the developmentally associated programmed cell death of tapetal cells necessary for microspore development. ROS have a role in regulation of female gametophyte patterning and maintenance of embryo sac polarity. During pollination, ROS play roles in the generation of self-incompatibility response during pollen-pistil interaction, pollen tube growth, pollen tube burst for sperm release and fertilization. In this mini review, we provide an overview of ROS production and signaling in the context of plant reproductive development, from female and male gametophyte development to fertilization.

Plants synthesize volatile organic compounds (VOCs) to attract pollinators and beneficial microorganisms, to defend themselves against herbivores and pathogens, and for plant-plant communication. In general, VOCs accumulate in and are emitted from the tissue of their biosynthesis. However, using biochemical and reverse genetic approaches, we demonstrate a new physiological phenomenon: inter-organ aerial transport of VOCs via natural fumigation. Before petunia flowers open, a tube-specific terpene synthase produces sesquiterpenes, which are released inside the buds and then accumulate in the stigma, potentially defending the developing stigma from pathogens. These VOCs also affect reproductive organ development and seed yield, which are previously unknown functions of terpenoid compounds. Bioactive sesquiterpenes accumulating in petunia stigmas are synthesized in the floral tube and then transported to the pistil via natural fumigation within the internal airspace of the developing flower.

During sexual reproduction in flowering plants such as Arabidopsis, a tip-growing pollen tube (PT) is guided to the synergid cells of the female gametophyte, where it bursts and releases the two sperm. Here we show that PT reception and powdery mildew (PM) infection, which involves communication between a tip-growing hypha and a plant epidermal cell, share molecular components. NORTIA (NTA), a member of the MLO family originally discovered in the context of PM resistance, and FERONIA (FER), a receptor-like kinase, both control PT reception in synergids. Homozygous fer mutants also display PM resistance, revealing a new function for FER and suggesting that conserved components, such as FER and distinct MLO proteins, are involved in both PT reception and PM infection.

Pollen tube (PT) reception in flowering plants describes the crosstalk between the male and female gametophytes upon PT arrival at the synergid cells of the ovule. It leads to PT growth arrest, rupture, and sperm cell release, and is thus essential to ensure double fertilization. Here, we describe TURAN (TUN) and EVAN (EVN), two novel members of the PT reception pathway that is mediated by the FERONIA (FER) receptor-like kinase (RLK). Like fer, mutations in these two genes lead to PT overgrowth inside the female gametophyte (FG) without PT rupture. Mapping by next-generation sequencing, cytological analysis of reporter genes, and biochemical assays of glycoproteins in RNAi knockdown mutants revealed both genes to be involved in protein N-glycosylation in the endoplasmic reticulum (ER). TUN encodes a uridine diphosphate (UDP)-glycosyltransferase superfamily protein and EVN a dolichol kinase. In addition to their common role during PT reception in the synergids, both genes have distinct functions in the pollen: whereas EVN is essential for pollen development, TUN is required for PT growth and integrity by affecting the stability of the pollen-specific FER homologs ANXUR1 (ANX1) and ANX2. ANX1- and ANX2-YFP reporters are not expressed in tun pollen grains, but ANX1-YFP is degraded via the ER-associated degradation (ERAD) pathway, likely underlying the anx1/2-like premature PT rupture phenotype of tun mutants. Thus, as in animal sperm-egg interactions, protein glycosylation is essential for the interaction between the female and male gametophytes during PT reception to ensure fertilization and successful reproduction.

Plant genomes encode isopentenyl phosphate kinases (IPKs) that reactivate isopentenyl phosphate (IP) via ATP-dependent phosphorylation, forming the primary metabolite isopentenyl diphosphate (IPP) used generally for isoprenoid/terpenoid biosynthesis. Therefore, the existence of IPKs in plants raises unanswered questions concerning the origin and regulatory roles of IP in plant terpenoid metabolism. Here, we provide genetic and biochemical evidence showing that IP forms during specific dephosphorylation of IPP catalysed by a subset of Nudix superfamily hydrolases. Increasing metabolically available IP by overexpression of a bacterial phosphomevalonate decarboxylase (MPD) in Nicotiana tabacum resulted in significant enhancement in both monoterpene and sesquiterpene production. These results indicate that perturbing IP metabolism results in measurable changes in terpene products derived from both the methylerythritol phosphate (MEP) and mevalonate (MVA) pathways. Moreover, the unpredicted peroxisomal localization of bacterial MPD led us to discover that the step catalysed by phosphomevalonate kinase (PMK) imposes a hidden constraint on flux through the classical MVA pathway. These complementary findings fundamentally alter conventional views of metabolic regulation of terpenoid metabolism in plants and provide new metabolic engineering targets for the production of high-value terpenes in plants. The origin and regulatory roles of isopentenyl phosphate (IP) in plant terpenoid metabolism remain unclear. Now, a study reports the enzymes for IP production and shows that these enzymes can be used to manipulate terpene production.

Sexual reproduction in flowering plants requires communication between synergid cells and a tip-elongating pollen tube (PT) for the successful delivery of sperm cells to the embryo sac. The reception of the PT relies on signaling within the synergid cell that ultimately leads to the degeneration of the receptive synergid and PT rupture, releasing the sperm cells for double fertilization. In Arabidopsis (Arabidopsis thaliana), NORTIA, a member of the MILDEW RESISTANCE LOCUS O (MLO) family of proteins, plays a critical role in the communication processes regulating PT reception. In this study, we determined that MLO function in PT reception is dependent on MLO protein localization into a Golgi-associated compartment before PT arrival, indicating that PT-triggered regulation of the synergid secretory system is important for synergid function during pollination. Additionally, a structure-function analysis revealed that MLO homooligomerization, mediated by the amino-terminal region of the protein, and carboxyl-terminal tail identity both contribute to MLO activity during PT reception.

The pollen tube in a flowering plant grows in a direction that is influenced by the mechanical properties of the stigma papillae and the organization of structures called cortical microtubules inside these cells.

In plants, organ formation and cell elongation require the constant adjustment of the dynamic and adaptable cell wall in response to environmental cues as well as internal regulators, such as light, mechanical stresses, pathogen attacks, phytohormones, and other signaling molecules. The molecular mechanisms that perceive these cues and translate them into cellular responses to maintain integrity and remodelling of the carbohydrate-rich cell wall for the coordination of cell growth are still poorly understood. In the last 3 years, the function of six membrane-localized receptor-like kinases (RLKs) belonging to the CrRLK1L family has been linked to the control of cell elongation in vegetative and reproductive development. Moreover, the presence of putative carbohydrate-binding domains in the extracellular domains of these CrRLK1Ls makes this receptor family an excellent candidate for coordinating cell growth, cell-cell communication, and constant cell wall remodelling during the plant life cycle.

• Large structural variations frequently occur in higher plants; however, the impact of such variations on plant diversification, adaptation and domestication remains elusive. • Here, we mapped and characterised a reciprocal chromosomal translocation in soybeans and assessed its effects on diversification and adaptation of wild (Glycine soja) and semiwild (Glycine gracilis) soybeans, and domestication of cultivated soybean (Glycine max), by tracing the distribution of the translocation in the USDA Soybean Germplasm Collection and population genetics analysis. • We demonstrate that the translocation occurred through CACTA transposon-mediated chromosomal breakage in wild soybean c. 0.34 Ma and is responsible for semisterility in translocation heterozygotes and reduces their reproductive fitness. The translocation has differentiated Continental (i.e. China and Russia) populations from Maritime (i.e. Korea and Japan) populations of G. soja and predominately adapted to cold and dry climates. Further analysis revealed that the divergence of G. max from G. soja predates the translocation event and that G. gracilis is an evolutionary intermediate between G. soja and G. max. • Our results highlight the effects of a chromosome rearrangement on the processes leading to plant divergence and adaptation, and provides evidence that suggests G. gracilis, rather than G. soja, as the ancestor of cultivated soybean.