Overview of pollen development. Male gametophyte development of angiosperms is a complex process that requires coordinated activity of different cell types and tissues of both gametophytic and sporophytic origin and the appropriate specific gene expression. Pollen ontogeny is also an excellent model for the dissection of cellular networks that control cell growth, polarity, cellular differentiation and cell signaling. This article describes two sequential phases of angiosperm pollen ontogenesis-developmental phase leading to the formation of mature pollen grains, and a functional or progamic phase, beginning with the impact of the grains on the stigma surface and ending at double fertilization. Here we present an overview of important cellular processes in pollen development and explosive pollen tube growth stressing the importance of reserves accumulation and mobilization and also the mutual activation of pollen tube and pistil tissues, pollen tube guidance and the communication between male and female gametophytes. We further describe the recent advances in regulatory mechanisms involved such as posttranscriptional regulation (including mass transcript storage) and posttranslational modifications to modulate protein function, intracellular metabolic signaling, ionic gradients such as Ca(2+) and H(+) ions, cell wall synthesis, protein secretion and intercellular signaling within the reproductive tissues.

• Klíčová slova
• Flowering plants, Male gametophyte, Pollen development, Pollen tube growth,
• MeSH
• Magnoliopsida růst a vývoj   metabolismus   MeSH
• pyl růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

Tobacco (Nicotiana tabacum L.) microspores at the time of mitosis are characterized by the abundant occurrence of 92- and 98-kDa glycoproteins (GP92 and GP98). GP92 is a soluble protein while GP98 is bound to the insoluble microspore fraction. Both glycoproteins were isolated by affinity chromatography and SDS-PAGE and analysed by MS. Peptide sequences were determined by mu-HPLC/nano-ESI-MS/MS (electrospray ionization tandem MS). GP92 displayed homology to beta-galactosidase (EC 3.2.1.23) and GP98 to beta-xylosidase (EC 3.2.1.37) from Arabidopsis thaliana (L.) Heynh. The activities of the two enzymes in microspore and pollen extracts of tobacco exhibited similar developmental changes to the occurrence of GP92 and GP98, with a maximum around microspore mitosis. These two glycoproteins are the first identified enzymes characteristic of mitotic microspores. Arabidopsis transcriptomic data for five beta-galactosidase and three beta-xylosidase genes abundantly expressed in pollen were verified by reverse transcription-PCR of RNA from different stages of Arabidopsis pollen development and from various parts of the sporophyte. The results showed abundant expression of two genes (At5g20710, At1g31740) homologous to tobacco GP92 in microspores and early pollen, and of three genes (At5g56870, At2g16730 and At4g35010) in maturing pollen. Analysis of beta-xylosidases showed abundant expression of a late pollen-specific gene At3g62710 and low expression of an early gene At5g10560. It is suggested that the early beta-galactosidase and beta-xylosidase genes may participate in cell wall loosening associated with pollen expansion after microspore mitosis and that the products of the late genes may play a role in cell expansion during pollen germination.

• MeSH
• 2D gelová elektroforéza MeSH
• Arabidopsis enzymologie   genetika   metabolismus   MeSH
• beta-galaktosidasa chemie   genetika   metabolismus   MeSH
• fylogeneze MeSH
• hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
• hmotnostní spektrometrie MeSH
• molekulová hmotnost MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• pyl enzymologie   genetika   růst a vývoj   MeSH
• sekvence nukleotidů MeSH
• sekvenční analýza hybridizací s uspořádaným souborem oligonukleotidů MeSH
• stanovení celkové genové exprese MeSH
• tabák enzymologie   genetika   růst a vývoj   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• xylosidasy chemie   genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• beta-galaktosidasa MeSH
• exo-1,4-beta-D-xylosidase MeSH Prohlížeč
• xylosidasy MeSH

BACKGROUND: The haploid male gametophyte generation of flowering plants consists of two- or three-celled pollen grains. This functional specialization is thought to be a key factor in the evolutionary success of flowering plants. Moreover, pollen ontogeny is also an attractive model in which to dissect cellular networks that control cell growth, asymmetric cell division and cellular differentiation. Our objective, and an essential step towards the detailed understanding of these processes, was to comprehensively define the male haploid transcriptome throughout development. RESULTS: We have developed staged spore isolation procedures for Arabidopsis and used Affymetrix ATH1 genome arrays to identify a total of 13,977 male gametophyte-expressed mRNAs, 9.7% of which were male-gametophyte-specific. The transition from bicellular to tricellular pollen was accompanied by a decline in the number of diverse mRNA species and an increase in the proportion of male gametophyte-specific transcripts. Expression profiles of regulatory proteins and distinct clusters of coexpressed genes were identified that could correspond to components of gametophytic regulatory networks. Moreover, integration of transcriptome and experimental data revealed the early synthesis of translation factors and their requirement to support pollen tube growth. CONCLUSIONS: The progression from proliferating microspores to terminally differentiated pollen is characterized by large-scale repression of early program genes and the activation of a unique late gene-expression program in maturing pollen. These data provide a quantum increase in knowledge concerning gametophytic transcription and lay the foundations for new genomic-led studies of the regulatory networks and cellular functions that operate to specify male gametophyte development.

• MeSH
• Arabidopsis genetika   MeSH
• CDC geny MeSH
• genetická transkripce genetika   MeSH
• genom rostlinný MeSH
• haploidie * MeSH
• homeodoménové proteiny genetika   MeSH
• proteiny huseníčku genetika   MeSH
• pyl genetika   MeSH
• rostlinné geny genetika   MeSH
• sekvenční analýza hybridizací s uspořádaným souborem oligonukleotidů metody   MeSH
• spory genetika   MeSH
• stanovení celkové genové exprese metody   MeSH
• transkripční faktory genetika   MeSH
• vývojová regulace genové exprese genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• homeodoménové proteiny MeSH
• KNAT5 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH
• transkripční faktory MeSH