Development and isolation of the male gametophyte of Torenia fournieri

The two sperm cells of Torenia fournieri are dimorphic. The dimorphic character suggests that they might be preferentially involved in fertilization during in vivo fusion with the egg cell and central cell. To probe the mechanism of preferential fertilization, it is necessary to use the most current molecular techniques. For this purpose, populations of >1000 individuals of the two dimorphic sperm cells, Sua (unassociated with the vegetative nucleus) and Svn (associated with the vegetative nucleus) were isolated from pollen tubes that had grown out of the cut ends of the styles. The two sperm cells released from pollen tubes remained attached to one another. When the two attached sperm cells were transferred into a solution containing 0.01% cellulose, 0.01% pectinase, and 5% mannitol, the connection between the two cells disappeared, and they were easily separated using a micromanipulator. The collection of these two individual populations containing over a thousand cells will permit research on gametic recognition at the molecular level.

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Isolation of two populations of sperm cells from the pollen tube of Torenia fournieri

Chen

Liao

Kuang³

et al. 2006

Plant Cell Rep

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Host range expansion in a powdery mildew fungus (Golovinomyces sp.) infecting Arabidopsis thaliana: Torenia fournieri as a new host

2006

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Since 2003, Torenia fournieri plants grown for experimental purposes were repeatedly infected by powdery mildew in a laboratory in Hungary. Based on morphological characteristics, the pathogen belonged to the mitosporic genus Oidium subgen. Reticuloidium, the anamorph stage of Golovinomyces. The rDNA ITS sequence was identical to that of two other powdery mildew fungi, infecting Arabidopsis and Veronica, respectively, in different parts of the world. According to a previous phylogenetic analysis of ITS and 28S rDNA sequences, those two powdery mildews belong to a recently evolved group of Golovinomyces characterized by multiple host range expansions during their evolution. Both the ITS sequence and the morphological data indicate that the powdery mildew anamorph infecting Torenia also belongs to this group. It is likely that the powdery mildew infections of the experimental T. fournieri plants, native to south-east Asia, were the result of a very recent host range expansion of a polyphagous Golovinomyces because (i) T. fournieri is absent from our region, except as an experimental plant grown in the laboratory, (ii) the powdery mildew fungus infecting this exotic plant belongs to a group of Golovinomyces where host range expansion is a frequent evolutionary scenario, (iii) cross-inoculation tests showed that this pathogen is also able to infect other plant species, notably A. thaliana and tobacco, and (iv) no Golovinomyces species are known to infect T. fournieri anywhere in the world. Although host range expansion has often been proposed as a common evolutionary process in the Erysiphales, and also in other biotrophic plant pathogens, this has not been clearly demonstrated in any case studies so far. To our knowledge, this is the first convincing case of a host range expansion event in the Erysiphales.Torenia fournieri (Scrophulariaceae) has been used widely in plant reproductive biology research and has long been grown from seeds for this purpose at our department at Eo¨tvo¨s University (e.g., Kristo´f and Imre, 1996;Imre and Kristo´f, 1999;Kristo´f et al., 1999;Va´gi et al., 2004). It is native to southeast Asia and it is not known to occur in the field in Hungary and neighbouring countries. Since 2003, severe powdery mildew infections were repeatedly observed on our potted T. fournieri plants in a laboratory. Intensively sporulating powdery mildew mycelia covered the stems, petioles, leaf lamina, and sepals of the plants (Figures 1 and 2). The infected parts withered and eventually died 3-4 weeks after the first symptoms appeared. As the disease was unwanted, we destroyed all the infected plants whenever the infection occurred, and produced new ones from seeds in different locations. In spite of these measures, severe infections occurred four times during the past 3 years.

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Evolutionary stasis in pollen morphogenesis due to natural selection

et al. 2015

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Summary The contribution of developmental constraints and selective forces to the determination of evolutionary patterns is an important and unsolved question. We test whether the long‐term evolutionary stasis observed for pollen morphogenesis (microsporogenesis) in eudicots is due to developmental constraints or to selection on a morphological trait shaped by microsporogenesis: the equatorial aperture pattern. Most eudicots have three equatorial apertures but several taxa have independently lost the equatorial pattern and have microsporogenesis decoupled from aperture pattern determination. If selection on the equatorial pattern limits variation, we expect to see increased variation in microsporogenesis in the nonequatorial clades. Variation of microsporogenesis was studied using phylogenetic comparative analyses in 83 species dispersed throughout eudicots including species with and without equatorial apertures. The species that have lost the equatorial pattern have highly variable microsporogenesis at the intra‐individual and inter‐specific levels regardless of their pollen morphology, whereas microsporogenesis remains stable in species with the equatorial pattern. The observed burst of variation upon loss of equatorial apertures shows that there are no strong developmental constraints precluding variation in microsporogenesis, and that the stasis is likely to be due principally to selective pressure acting on pollen morphogenesis because of its implication in the determination of the equatorial aperture pattern.

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Development and isolation of the male gametophyte of Torenia fournieri

Cited by 3 publications

References 56 publications

Isolation of two populations of sperm cells from the pollen tube of Torenia fournieri

Isolation of two populations of sperm cells from the pollen tube of Torenia fournieri

Host range expansion in a powdery mildew fungus (Golovinomyces sp.) infecting Arabidopsis thaliana: Torenia fournieri as a new host

Evolutionary stasis in pollen morphogenesis due to natural selection

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