Dataset Information

New views of tapetum ultrastructure and pollen exine development in Arabidopsis thaliana.

ABSTRACT:

Background and aims

The Arabidopsis thaliana pollen cell wall is a complex structure consisting of an outer sporopollenin framework and lipid-rich coat, as well as an inner cellulosic wall. Although mutant analysis has been a useful tool to study pollen cell walls, the ultrastructure of the arabidopsis anther has proved to be challenging to preserve for electron microscopy.

Methods

In this work, high-pressure freezing/freeze substitution and transmission electron microscopy were used to examine the sequence of developmental events in the anther that lead to sporopollenin deposition to form the exine and the dramatic differentiation and death of the tapetum, which produces the pollen coat.

Key results

Cryo-fixation revealed a new view of the interplay between sporophytic anther tissues and gametophytic microspores over the course of pollen development, especially with respect to the intact microspore/pollen wall and the continuous tapetum epithelium. These data reveal the ultrastructure of tapetosomes and elaioplasts, highly specialized tapetum organelles that accumulate pollen coat components. The tapetum and middle layer of the anther also remain intact into the tricellular pollen and late uninucleate microspore stages, respectively.

Conclusions

This high-quality structural information, interpreted in the context of recent functional studies, provides the groundwork for future mutant studies where tapetum and microspore ultrastructure is assessed.

SUBMITTER: Quilichini TD

PROVIDER: S-EPMC4195548 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Publications

New views of tapetum ultrastructure and pollen exine development in Arabidopsis thaliana.

Quilichini Teagen D TD Douglas Carl J CJ Samuels A Lacey AL

Annals of botany 20140409 6

<h4>Background and aims</h4>The Arabidopsis thaliana pollen cell wall is a complex structure consisting of an outer sporopollenin framework and lipid-rich coat, as well as an inner cellulosic wall. Although mutant analysis has been a useful tool to study pollen cell walls, the ultrastructure of the arabidopsis anther has proved to be challenging to preserve for electron microscopy.<h4>Methods</h4>In this work, high-pressure freezing/freeze substitution and transmission electron microscopy were u ...[more]

PMID: 24723448

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Project description:BACKGROUND: To understand transcriptional regulatory networks (TRNs), especially the coordinated dynamic regulation between transcription factors (TFs) and their corresponding target genes during development, computational approaches would represent significant advances in the genome-wide expression analysis. The major challenges for the experiments include monitoring the time-specific TFs' activities and identifying the dynamic regulatory relationships between TFs and their target genes, both of which are currently not yet available at the large scale. However, various methods have been proposed to computationally estimate those activities and regulations. During the past decade, significant progresses have been made towards understanding pollen development at each development stage under the molecular level, yet the regulatory mechanisms that control the dynamic pollen development processes remain largely unknown. Here, we adopt Networks Component Analysis (NCA) to identify TF activities over time course, and infer their regulatory relationships based on the coexpression of TFs and their target genes during pollen development. RESULTS: We carried out meta-analysis by integrating several sets of gene expression data related to Arabidopsis thaliana pollen development (stages range from UNM, BCP, TCP, HP to 0.5 hr pollen tube and 4 hr pollen tube). We constructed a regulatory network, including 19 TFs, 101 target genes and 319 regulatory interactions. The computationally estimated TF activities were well correlated to their coordinated genes' expressions during the development process. We clustered the expression of their target genes in the context of regulatory influences, and inferred new regulatory relationships between those TFs and their target genes, such as transcription factor WRKY34, which was identified that specifically expressed in pollen, and regulated several new target genes. Our finding facilitates the interpretation of the expression patterns with more biological relevancy, since the clusters corresponding to the activity of specific TF or the combination of TFs suggest the coordinated regulation of TFs to their target genes. CONCLUSIONS: Through integrating different resources, we constructed a dynamic regulatory network of Arabidopsis thaliana during pollen development with gene coexpression and NCA. The network illustrated the relationships between the TFs' activities and their target genes' expression, as well as the interactions between TFs, which provide new insight into the molecular mechanisms that control the pollen development.

Project description:BACKGROUND:As one of the main crops in the world, sterility of rice (Oryza sativa L.) significantly affects the production and leads to yield decrease. Our previous research showed that OsPUB73, which encodes U-box domain-containing protein 73, may be associated with male sterility. However, little information is available on this gene that is required for anther development. In the present study, we knocked out OsPUB73 by using the CRISPR/Cas9 system and studied the cytological and transcriptome of the gene-defect associated with pollen development and sterility in the rice variety (Taichung 65). RESULTS:The sequence analysis indicated that OsPUB73 was comprised of 3 exons and 2 introns, of which CDS encoded 586 amino acids including a U-box domain. The expression pattern of OsPUB73 showed that it was highly expressed in the anther during meiosis stage. The ospub73 displayed low pollen fertility (19.45%), which was significantly lower than wild type (WT) (85.37%). Cytological observation showed tapetum vacuolated at the meiosis stage and pollen exine was abnormal at the bi-cellular pollen stage of ospub73. RNA-seq analysis detected 2240 down and 571 up-regulated genes in anther of ospub73 compared with WT during meiosis stage. Among of 2240 down-regulated genes, seven known genes were associated with tapetal cell death or pollen exine development, including CYP703A3 (Cytochrome P450 Hydroxylase703A3), CYP704B2 (Cytochrome P450 Hydroxylase704B2), DPW (Defective Pollen Wall), PTC1 (Persistant Tapetal Cell1), UDT1 (Undeveloped Tapetum1), OsAP37 (Aspartic protease37) and OsABCG15 (ATP binding cassette G15), which were validated by quantitative real-time polymerase chain reaction (qRT-PCR). These results suggested OsPUB73 may play an important role in tapetal or pollen exine development and resulted in pollen partial sterility. CONCLUSION:Our results revealed that OsPUB73 plays an important role in rice male reproductive development, which provides valuable information about the molecular mechanisms of the U-box in rice male reproductive development.

Dataset Information

New views of tapetum ultrastructure and pollen exine development in Arabidopsis thaliana.

Background and aims

Methods

Key results

Conclusions

Publications

New views of tapetum ultrastructure and pollen exine development in Arabidopsis thaliana.

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