The seeds and fruits derived from the sexual reproduction of flowering plants constitute the major part of the human diet. Our capacity to generate sufficient crop yield is increasingly compromised by human population expansion, competition for land use, biodiversity loss, and global climate change. Hot days and heat waves are predicted to increase in frequency and intensity in many temperate r...

The effect of anther-derived substances on pollen function was studied using pollen produced by in vitro culture of immature pollen of tobacco (Nicotiana tabacum L.) and petunia (Petunia hybrida). Addition of conditioned medium consisting of diffusates from in situ matured pollen strongly increased pollen germination frequency and pollen tube growth, as well as seed set after in situ pollinatio...

Pollen development and male gametogenesis are critically dependent upon cell polarization leading to a highly asymmetric cell division termed pollen mitosis I. A mutational approach was adopted in Arabidopsis thaliana to identify genes involved these processes. Four independent gemini pollen mutants were isolated which produce divided or twin-celled pollen. The gemini pollen1 mutant was charact...

Starch biosynthesis during pollen maturation is not well understood in terms of genes/proteins and intracellular controls that regulate it in developing pollen. We have studied two specific developmental stages: "early," characterized by the lack of starch, before or during pollen mitosis I; and "late," an actively starch-filling post-pollen mitosis I phase in S-type cytoplasmic male-sterile (S...

The interdependence of cell cycle control, chromatin remodeling and cell fate determination remains unclear in flowering plants. Pollen development provides an interesting model, as it comprises only two cell types produced by two sequential cell divisions. The first division separates the vegetative cell from the generative cell. The generative cell divides and produces the two sperm cells, tr...

Male gametogenesis was cytologically analyzed in wheat lines homozygous or hemizygous for gametocidal (Gc) factors with different modes of action. The first and second meiotic divisions in all lines were cytologically normal. The postmeiotic mitoses were normal in the homozygous lines; however, chromosome fragments and bridges were observed in the mitoses of the hemizygous lines. The morphology...

Weed pollen grains belonging to the Asteraceae family contain a variety of allergens inducing type I and IV allergies in susceptible people. The aim of this research was to compare the allergenic properties of immature and mature Shasta daisy pollen grains (Chrysanthemum maximum Ramond) to define the potential role of the maturation process on the allergenicity of Asteraceae pollen grains. The ...

Potassium antimonite was used to locate calcium in the anthers of Torenia fournieri (Linderniaceae). Abundant calcium precipitates accumulate in the microsporocyte cytoplasm. After meiosis, calcium precipitates are abundant on the microspore wall, as well as the callosic wall of each tetraspore. A large number of calcium precipitates also occur on the outer membranes of the tapetal cells, and i...

Vesicle traffic between the endoplasmic reticulum and the Golgi apparatus in mammals requires the small GTP-binding protein Rab2, but Saccharomyces cerevisiae appears not to have a Rab2 homolog. Here it is shown that the higher plant, Arabidopsis thaliana, contains a gene, At-RAB2, whose predicted product shares 79% identity with human Rab2 protein. Transgenic plants containing fusions between ...