Apomixis at a high resolution: unravelling diplospory in Asteraceae.

Apomictic plants are able to produce clonal seeds. This reproductive system allows the one-step fixation of any valuable trait for subsequent generations and would pave the way for a revolution in the agricultural system. Despite that, the introduction of apomixis in sexually reproducing crops has been hampered due to the difficulty in characterising its genetic regulation.

Mendel's terminology and notation reveal his understanding of genetics.

We describe both the terminology and use of symbols introduced by Mendel in his 1866 paper and discuss some misconceptions concerning their interpretation.

Gregor Mendel and the theory of species multiplication.

According to the revisionist interpretation of Mendel's pea crosses, his primary aim was not to study the inheritance of traits. Instead, he was interested in the question raised by Linnaeus as to whether new species could arise from the hybridization of existing species. The genetic interpretation is therefore seen as ahistorical by the revisionists.

Asexual reproduction through seeds: the complex case of diplosporous apomixis.

Apomixis is considered a potentially revolutionary tool to generate high-quality food at a lower cost and shorter developmental time due to clonal seed production through apomeiosis and parthenogenesis. In the diplosporous type of apomixis, meiotic recombination and reduction are circumvented either by avoiding or failing meiosis or by a mitotic-like division. Here, we review the literature on diplospory, from early cytological studies dating back to the late 19th century to recent genetic findings.

How did Mendel arrive at his discoveries?

There are few historical records concerning Gregor Johann Mendel and his work, so theories abound concerning his motivation. These theories range from Fisher's view that Mendel was testing a fully formed previous theory of inheritance to Olby's view that Mendel was not interested in inheritance at all, whereas textbooks often state his motivation was to understand inheritance. In this Perspective, we review current ideas about how Mendel arrived at his discoveries and then discuss an alternative scenario based on recently discovered historical sources that support the suggestion that Mendel's fundamental research on the inheritance of traits emerged from an applied plant breeding program.

A PARTHENOGENESIS allele from apomictic dandelion can induce egg cell division without fertilization in lettuce.

Apomixis, the clonal formation of seeds, is a rare yet widely distributed trait in flowering plants. We have isolated the PARTHENOGENESIS (PAR) gene from apomictic dandelion that triggers embryo development in unfertilized egg cells. PAR encodes a K2-2 zinc finger, EAR-domain protein.

Genetic Dissection of Apomixis in Dandelions Identifies a Dominant Parthenogenesis Locus and Highlights the Complexity of Autonomous Endosperm Formation.

Apomixis in the common dandelion () consists of three developmental components: diplospory (apomeiosis), parthenogenesis, and autonomous endosperm development. The genetic basis of diplospory, which is inherited as a single dominant factor, has been previously elucidated. To uncover the genetic basis of the remaining components, a cross between a diploid sexual seed parent and a triploid apomictic pollen donor was made.

Mendel's pea crosses: varieties, traits and statistics.

A controversy arose over Mendel's pea crossing experiments after the statistician R.A. Fisher proposed how these may have been performed and criticised Mendel's interpretation of his data.

How Mendel's Interest in Inheritance Grew out of Plant Improvement.

Despite the fact that Gregor Mendel is generally respected as the founder of genetics, little is known about the origin of and motivation for his revolutionary work. No primary sources are known that discuss his work during the period of his pea crossing experiments. Here, we report on two previously unknown interconnected local newspaper articles about Mendel's work that predate his famous lectures by 4 years.

The Full Breadth of Mendel's Genetics.

Gregor Mendel's "Experiments on Plant Hybrids" (1865/1866), published 150 years ago, is without doubt one of the most brilliant works in biology. Curiously, Mendel's later studies on Hieracium (hawkweed) are usually seen as a frustrating failure, because it is assumed that they were intended to confirm the segregation ratios he found in Pisum Had this been his intention, such a confirmation would have failed, since, unknown to Mendel, Hieracium species mostly reproduce by means of clonal seeds (apomixis). Here we show that this assumption arises from a misunderstanding that could be explained by a missing page in Mendel's first letter to Carl Nägeli.

Fine mapping of Restorer-of-fertility in pepper (Capsicum annuum L.) identified a candidate gene encoding a pentatricopeptide repeat (PPR)-containing protein.

Using fine mapping techniques, the genomic region co-segregating with Restorer - of - fertility ( Rf ) in pepper was delimited to a region of 821 kb in length. A PPR gene in this region, CaPPR6 , was identified as a strong candidate for Rf based on expression pattern and characteristics of encoding sequence. Cytoplasmic-genic male sterility (CGMS) has been used for the efficient production of hybrid seeds in peppers (Capsicum annuum L.

Plant Breeding: Surprisingly, Less Sex Is Better.

Introduction of apomixis, asexual reproduction through seeds, into crop species has the potential to dramatically transform plant breeding. A new study demonstrates that traits can be stably transferred between generations in newly produced apomictic lines, and heralds a breeding revolution needed to increase food production for the growing planet.

Fluorescent in situ hybridization shows DIPLOSPOROUS located on one of the NOR chromosomes in apomictic dandelions (Taraxacum) in the absence of a large hemizygous chromosomal region.

Apomixis in dandelions (Taraxacum: Asteraceae) is encoded by two unlinked dominant loci and a third yet undefined genetic factor: diplosporous omission of meiosis (DIPLOSPOROUS, DIP), parthenogenetic embryo development (PARTHENOGENESIS, PAR), and autonomous endosperm formation, respectively. In this study, we determined the chromosomal position of the DIP locus in Taraxacum by using fluorescent in situ hybridization (FISH) with bacterial artificial chromosomes (BACs) that genetically map within 1.2-0.

Genetic fine-mapping of DIPLOSPOROUS in Taraxacum (dandelion; Asteraceae) indicates a duplicated DIP-gene.

Background: DIPLOSPOROUS (DIP) is the locus for diplospory in Taraxacum, associated to unreduced female gamete formation in apomicts. Apomicts reproduce clonally through seeds, including apomeiosis, parthenogenesis, and autonomous or pseudogamous endosperm formation. In Taraxacum, diplospory results in first division restitution (FDR) nuclei, and inherits as a dominant, monogenic trait, independent from the other apomixis elements.

Changes in genomic methylation patterns during the formation of triploid asexual dandelion lineages.

DNA methylation is an epigenetic mechanism that has the potential to affect plant phenotypes and that is responsive to environmental and genomic stresses such as hybridization and polyploidization. We explored de novo methylation variation that arises during the formation of triploid asexual dandelions from diploid sexual mother plants using methylation-sensitive amplified fragment length polymorphism (MS-AFLP) analysis. In dandelions, triploid apomictic asexuals are produced from diploid sexual mothers that are fertilized by polyploid pollen donors.

Stress-induced DNA methylation changes and their heritability in asexual dandelions.

*DNA methylation can cause heritable phenotypic modifications in the absence of changes in DNA sequence. Environmental stresses can trigger methylation changes and this may have evolutionary consequences, even in the absence of sequence variation. However, it remains largely unknown to what extent environmentally induced methylation changes are transmitted to offspring, and whether observed methylation variation is truly independent or a downstream consequence of genetic variation between individuals.

Mendelian genetics of apomixis in plants.

Apomixis, asexual reproduction through seeds, has the potential to revolutionize agriculture if its genetic basis can be elucidated. However, the genetic control of natural apomixis has remained obscure until quite recently, owing to all the complications of Mendelian genetics, such as epistatic gene interactions, components that are expressed sporophytically and gametophytically, expression modifiers, polyploidy, aneuploidy, segregation distortion, suppressed recombination, etc., that seem to have accumulated during the evolution of apomixis.

Pollinating fig wasps: genetic consequences of island recolonization.

The levels of genetic diversity and gene flow may influence the long-term persistence of populations. Using microsatellite markers, we investigated genetic diversity and genetic differentiation in island (Krakatau archipelago, Indonesia) and mainland (Java and Sumatra, Indonesia) populations of Liporrhopalum tentacularis and Ceratosolen bisulcatus, the fig wasp pollinators of two dioecious Ficus (fig tree) species. Genetic diversity in Krakatau archipelago populations was similar to that found on the mainland.

Formation of unreduced megaspores (diplospory) in apomictic dandelions (Taraxacum officinale, s.l.) is controlled by a sex-specific dominant locus.

In apomictic dandelions, Taraxacum officinale, unreduced megaspores are formed via a modified meiotic division (diplospory). The genetic basis of diplospory was investigated in a triploid (3x = 24) mapping population of 61 individuals that segregated approximately 1:1 for diplospory and meiotic reduction. This population was created by crossing a sexual diploid (2x = 16) with a tetraploid diplosporous pollen donor (4x = 32) that was derived from a triploid apomict.

Ecological and evolutionary opportunities of apomixis: insights from Taraxacum and Chondrilla.

The ecological and evolutionary opportunities of apomixis in the short and the long term are considered, based on two closely related apomictic genera: Taraxacum (dandelion) and Chondrilla (skeleton weed). In both genera apomicts have a wider geographical distribution than sexuals, illustrating the short-term ecological success of apomixis. Allozymes and DNA markers indicate that apomictic populations are highly polyclonal.