Biomedical subjects

David Twell

Publications and source records attributed to David Twell.

21 records · Page 2Linked to original sources

PubMed2003

Comparative analysis of the Arabidopsis pollen transcriptome.

We present a genome-wide view of the male gametophytic transcriptome in Arabidopsis based on microarray analysis. In comparison with the transcriptome of the sporophyte throughout development, the pollen transcriptome showed reduced complexity and a unique composition. We identified 992 pollen-expressed mRNAs, nearly 40% of which were detected specifically in pollen. Analysis of the functional composition of the pollen transcriptome revealed the over-representation of mRNAs encoding proteins involved in cell wall metabolism, cytoskeleton, and signaling and under-representation of mRNAs involved in transcription and protein synthesis. For several gene families, we observed a common pattern of mutually exclusive gene expression between pollen and sporophytic tissues for different gene family members. Our results provide a 50-fold increase in the knowledge of genes expressed in Arabidopsis pollen. Moreover, we also detail the extensive overlap (61%) of the pollen transcriptome with that of the sporophyte, which provides ample potential to influence sporophytic fitness through gametophytic selection.

Arabidopsis↗

PubMed2002

MOR1/GEM1 has an essential role in the plant-specific cytokinetic phragmoplast.

MOR1 is a member of the MAP215 family of microtubule-associated proteins and is required to establish interphase arrays of cortical microtubules in plant cells. Here we show that MOR1 binds microtubules in vivo, localizing to both cortical microtubules and to areas of overlapping microtubules in the phragmoplast. Genetic complementation of the cytokinesis-defective gemini pollen 1-1 (gem1-1) mutation with MOR1 shows that MOR1 (which is synonymous with the protein GEM1) is essential in cytokinesis. Phenotypic analysis of gem1-1 and gem1-2, which contains a T-DNA insertion, confirm that MOR1/GEM1 is essential for regular patterns of cytokinesis. Both the gem1-1 and gem1-2 mutations cause the truncation of the MOR1/GEM1 protein. In addition, the carboxy-terminal domain of the protein, which is absent in both mutants, binds microtubules in vitro. Our data show that MOR1/GEM1 has an essential role in the cytokinetic phragmoplast.

Amino Acid Sequence↗

PubMed2002

Genetic control of male germ unit organization in Arabidopsis.

In flowering plants, the vegetative nucleus and the two sperm cells are proposed to form a functional assemblage, the male germ unit (MGU). Here, we describe the developmental pathway of MGU assembly in Arabidopsis and report two classes of mutations that affect the integrity and/or the positioning of the MGU in the mature pollen grain. In germ unit malformed (gum) mutants, the vegetative nucleus is positioned adjacent to the pollen grain wall, separate from the two sperm cells, whereas in MGU displaced (mud) mutants, the intact MGU is displaced to the pollen grain wall. mud and gum mutants correspond to male-specific gametophytic mutations that also reduce pollen fitness. Genetic mapping showed that the gum1 and gum2 mutations are genetically linked, possibly allelic, whereas the mud1 and mud2 mutations correspond to two unlinked loci mapping on different chromosomes. The hierarchical relationship between mud and gum mutations was investigated by phenotypic analysis of double mutants. gum1 appeared to act earlier than mud1 and mud2, affecting initial MGU assembly and its stability during pollen maturation. In contrast, mud1 and mud2 mutations appear to act only on MGU positioning during final maturation. From in planta analyses of pollen germination in mud and gum mutants, we conclude that the initial proximity and positioning of MGU components is not required for their entrance into the pollen tube, but the efficiency of MGU translocation is reduced.

Arabidopsis↗