Flowering represents a major physiological developmental transition from vegetative to reproductive development in the plant life cycle. It is the central cue in plant development and is determined by the control of both intrinsic genetics and environmental factors such as low temperature and photoperiod. Many genes related to flowering have been isolated in Arabidopsis, and a genetic network of the flowering process has been mapped. Histone methylation plays an important role in the regulation of plant development. Great progress has been achieved with histone modification in regulating flowering. This paper reviews the epigenetic research into histone lysine methylation in plant flowering. We also review new directions and expectations in this research field.

As the model species of monocotyledons, rice (Oryza sativa) is being widely studied in terms of reproduction. Forward and reverse genetic approaches have resulted in the cloning of some important genes controlling reproductive development such as floral organ number, and great progress has been made in revealing the molecular mechanisms of rice floral organ development during the past few years. This article reviews the recent progress in this field.

Male gametogenesis is one of the key steps in plant sexual reproduction and is essential for the alternation between the diploid sporophytic phase and haploid gametophytic phase in the life cycle of higher plants. In recent years, rapid progress has been made in identifying the genes that play key roles in this process by use of DNA insertion mutagenesis. This article reviews the genetic and molecular mechanisms that control the formation of germline cells and male gametophytes and their interactions with surrounding somatic cells in plant.

Female gametogenesis in higher plants undergoes various developmental changes, including the de novo formation of germline cells, the differentiation of the megaspore mother cell, meiosis, megaspore selection, and the development of the embryosac. Therefore, the system is excellent for dissecting these fundamental processes at both the genetic and molecular levels. This review discusses the recent findings about these processes, with a focus on the model plant Arabidopsis.

Male gametogenesis in flowering plants is the main function executing sexual reproduction, so the focus of plant scientists is study of the development of male gametogenesis. For both the model species Arabidopsis thaliana and rice (Oryza sativa), the completion of the genome sequence has made possible study of pollen development at the genome level. This review focuses on recent advances in pollen transcriptomics of A. thaliana.

Pollen is a highly reduced organism that plays a great role in plant sexual reproduction as the male gametophyte. Much research has focused on the molecular mechanism of pollen development, the interaction with the pistil, germination, and pollen tube growth. In recent years, high-throughput proteomic approaches allowing for proteomic investigation of the pollen of rice, Arabidopsis and gymnosperms have led to characterization of a functional category of proteins expressed in pollen. Proteins involved in wall remodeling and metabolism, protein metabolism, cytoskeletal dynamics and signal transduction are highly represented in pollen, and 25% of proteins appear as multi-isoforms. This paper gives an overview of recent pollen proteomic investigations.

Within the rice anther, meiosis of the pollen mother cell produces microspores, which further develop into pollen grains. Then the mature pollen is released from the dehiscesd anther, and pollination occurs. Molecular studies have identified some genes participating in this process, including those regulating anther cell division and differentiation, controlling male meiosis, supporting pollen development, and promoting anther dehiscence. The rice pollen development process and its molecular mechanisms are reviewed in this article.

The pollen tube is the polarized tip-growing system that involves a complicated kinetic process essential for sexual reproduction in higher plants. The process of pollen tube growth involves many aspects, especially the dynamics of the cytoskeleton and cytoplasmic movement. The present paper reviews the structure of the pollen tube, cytoskeleton, and vesicles, as well as mitochondria trafficking and vesicle recycling in pollen tubes.

The double fertilization characteristic of angiosperms involves two separate fusion events. The process occurs deep within maternal tissues, and therefore, has been a particularly difficult field in the study of sexual plant reproduction. In recent years, the successful construction of cDNA libraries of gametes in several species, the development of in vitro experimental systems, and the application of new molecular and genetic approaches have thrown new light on the field for deeper insight into the molecular and cellular mechanisms underlying the fertilization process. In the present review, we focus on some of the recent advances and some key developmental events revealed in the fertilization process, including the role of the egg apparatus in guiding pollen tube orientation, sperm cell movement to their targeting cells, interaction between gametes, egg cell activation, and onset of embryogenesis and endosperm development.

To avoid inbreeding and promote out-crossing, many flowering plants have adopted self-incompatibility (SI) systems, through which incompatible (self or genetically related) pollen is recognized and rejected, whereas compatible (non-self) pollen is allowed to grow in the style to deliver the germ cells to the ovary for double fertilization. Among various SI systems, gametophytic SI in Solanaceae, Scrophulariaceae and Rosaceae appears to be the most common whereby the specificity of SI response is controlled by a single polymorphic S-locus. Recent studies have shown that the S-locus is organized in a haplotype fashion and carries at least two genes determining the recognition specificity: S-ribonucleases expressed in the pistil (pistil-S) and S-locus Fbox(SLF) genes in the pollen (pollen-S). Here we discuss recent data on the possible molecular mechanisms eliciting the S-RNasebased self-incompatibility response.

Plant embryogenesis is a tightly regulated developmental process, consisting of zygote activation, cell division and differentiation, polarity establishment, pattern formation, organogenesis, storage product accumulation, and eventually the formation of a mature embryo. Research in the last twenty years has identified many genes that are involved in different stages of the embryo development, which provides important information underlying plant embryogenesis. This review focuses on the progresses made in this area with emphasis on early embryogenesis. At the end, we give a brief outline about the unsolved problems and the prospective for future studies.

Cytoplasmic male sterility (CMS), a maternally inherited trait, is widespread among plant species. Because of the importance of CMS in hybrid seed production, understanding the molecular basis of CMS and its restoration is critical for better utilization of heterosis in crops. A number of CMS and restorer genes have been isolated, and the molecular mechanisms for the CMS-restoration interaction of some systems have been elucidated. In this paper, we review the progress in study of CMS and restorer genes in plants.

Seed mucilage consists of pectin polysaccharides that are secreted by the Golgi apparatus in epidermal cells to the cell cavity and cell walls of the seed coat, which swells considerably upon wetting. Mucilagineous seeds commonly are found in species of Brassicaceae, Asteraceae, Plantaginaceae and several other flowering plant families. Many taxa with mucilageous seeds occur in deserts. Seed mucilage is ecologically advantageous for seed dispersal, germination, seedling development and protection of seed, and thus it is an adaptation of plants to deserts and sand dunes. In addition to furthering our understanding of the ecological and evolutionary aspects of desert plants to their environment, research on mucilaginous seeds will be helpful in building a model system for exploring gene control mechanisms of carbohydrate synthesis and secretion, secondary cell wall biosynthesis and cell morphogenesis. In this paper, we review recent advances on mucilaginous seeds, with emphasis on (1)chemical composition of seed mucilage; (2)morphological characteristics of mucilaginous seed coats and mucilage; (3) biochemical processes in and genetic regulation of differentiation of mucilage-secreting cells, mucilage biosynthesis and mucilage secretion in the seed coat; and (4) ecological significance of seed mucilage. Finally, prospects for further research in this area are discussed. Our purpose is to promote research on the seed biology of desert plants in China and to provide additional justification for protection of biodiversity and for ecological conservation in the desert region of northwest China.

Paraffin wax specimens of Bupleurum chinense DC. were used to observe the whole process of embryo development, including megasporgenesis, microsporgenesis, and the development of female and male gametophytes. The anther is tetrasporangiate and its wall conforms to the Dicotyledonous type developmentally. The anther wall includes 4 layers: epiderm, endothecium, middle layer and tapetum. Simultaneous cytokinesis in the microspore mother cells follows meiosis, and the microspore tetrads are tetrahedral. Pollen grains are 3 celled when shed. The ovule is anatropous, unitegmic and tenuinucellar. Usually one archesporium functions directly as a megaspore mother cell. Cytokinesis in the megaspore mother cell usually accompanies meiosis, and the chalazal megaspore of a linear or T-shape tetrad develops into a Polygonum-type embryo sac. The innermost layer of the integument differentiates as an endothelium tapetum. In the same bud, the stamen develops earlier than the pistil. We compared the bud size and development stage of pistils and stamens.