Gene expression profiling of the different stages of Arabidopsis thaliana trichome development on the single cell level
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany. Plant Physiology and Biochemistry
(Impact Factor: 2.76).
03/2008; 46(2):160-73. DOI: 10.1016/j.plaphy.2007.11.001
Leaf hairs (trichomes) of Arabidopsis thaliana are a model system for studying cell development, differentiation and cell cycle regulation. To exploit this model system with ultimate spatial resolution we applied single cell sampling, thus avoiding the averaging effect induced by complex tissue mixtures. In particular, we analysed gene expression profiles of two selected stages of the developing trichome: trichome initial cells and mature trichomes, as well as pavement cells. Ten single cells per sample were collected by glass microcapillaries and used for the generation of radioactive probes for subsequent hybridization to nylon filters representing approximately 8000 genes of A. thaliana. Functional categorization of genes transcribed in trichome initials, mature trichomes and pavement cells demonstrated involvement of these surface cells in the stress response. In silico promoter analysis of genes preferentially expressed in trichome initials revealed enrichment in MYB-binding sites and presence of elements involved in hormonal, metal, sulphur response and cell cycle regulation. Three candidate genes preferentially expressed in trichome initials were selected for further analysis: At3g16980 (putative RNA polymerase II), At5g15230 (GASA4) and At4g27260 (GH3.5, WES1). Promoter:GUS studies confirmed expression of the putative RNA polymerase II and the gibberellin responsive GASA4 in trichome initials and partially in mature trichomes. Functional implication of the three selected candidates in trichome development and hence in cell cycle regulation in A. thaliana is discussed. We suggest that these genes are involved in differentiation and initiation of endocycling during trichome development.
Available from: Cimen Atak
- "The GLABROUS 1 (GL1) and TRANSPARENT TESTA GLABRA 1 (TTG1) genes are the major genes in trichome initiation and leaf trichome spacing. TTG1 encodes a WD-40 repeat-containing protein (Szymanski et al. 1998; Hauser et al. 2001; Gonzáles et al., 2008; Kryvych et al., 2008; Yan et al., 2012), and the GLABRA2 (GL2) gene has similarity to homeodomain proteins. GL2 is an environmental change-sensitive gene and is regulated by the TTG1 and GL1 and WEREWOLF (WER) genes (Rerie et al. 1994; Masucci et al. 1996; Marks 1997; Szymanski et al. 1998). "
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ABSTRACT: This is the first report on soybean with the aim to show the effects of gamma radiation on trichome metabolim. Soybean seeds were subjected to 300 Gy gamma radiation at a dose rate of 10 Gy/min using a Cs-137 gamma source. The photosynthetic pigment, total protein content and ascorbate peroxidase activity were studied. The results showed that the chlorophyll a content was decreased by 80% on day 14 and by 77% on day 21 of irradiation. The chlorophyll b content was reduced by 58.6% and 62.06% on day 14 and 21 after irradiation, respectively. The total carotenoid concentration was reduced by 81.14% on the 14th day after irradiation and by 91% on the 21st day of irradiation, compared to control. The total protein concentration was found to have decreased significantly at 14 and 21 day after treatment. High level of ascorbate peroxidase (APX) activity was recorded in the leaves developed from irradiated soybean seeds, compared to the non-irradiated group. The trichome densities were 6.76 fold increased at 21 day of irradiation, while the stomatal densities were decreased, compared to control. We also performed a qRT-PCR analysis to detect the transcription levels of the soybean trichome developmental genes. The GL2 and CPC genes were up-regulated (P≤0.05). The results of this study pointed out that the CPC transcription factor has to be study in further studies to provide an insight on its exact role in regulation of trichome development in soybean under radiation stress.
Available from: Jacob Pollier
- "Although the form and function of plant cells are strongly correlated, the processes that determine the cell shape remain largely unknown. Plant cell morphogenesis is regulated in a non-cell-autonomous fashion by the surrounding tissues , hormone interference during ontogenesis, and sometimes by polyploidy as a consequence of endoreduplication [2,3]. In contrast, in unicellular relatives of land plants, it is possible to study the endogenous controls of cell morphogenesis without the interference by interacting cells and to better understand how these mechanisms have evolved in the green lineage. "
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ABSTRACT: Streptophyte green algae share several characteristics of cell growth and cell wall formation with their relatives, the embryophytic land plants. The multilobed cell wall of Micrasterias denticulata that rebuilds symmetrically after cell division and consists of pectin and cellulose, makes this unicellular streptophyte alga an interesting model system to study the molecular controls on cell shape and cell wall formation in green plants.
Genome-wide transcript expression profiling of synchronously growing cells identified 107 genes of which the expression correlated with the growth phase. Four transcripts showed high similarity to expansins that had not been examined previously in green algae. Phylogenetic analysis suggests that these genes are most closely related to the plant EXPANSIN A family, although their domain organization is very divergent. A GFP-tagged version of the expansin-resembling protein MdEXP2 localized to the cell wall and in Golgi-derived vesicles. Overexpression phenotypes ranged from lobe elongation to loss of growth polarity and planarity. These results indicate that MdEXP2 can alter the cell wall structure and, thus, might have a function related to that of land plant expansins during cell morphogenesis.
Our study demonstrates the potential of M. denticulata as a unicellular model system, in which cell growth mechanisms have been discovered similar to those in land plants. Additionally, evidence is provided that the evolutionary origins of many cell wall components and regulatory genes in embryophytes precede the colonization of land.
Available from: M. David Marks
- "Cells in the interior of the resulting trichome clusters undergo little endoreduplication or expansion, and resemble early stage developing trichomes. These trichomes express high levels of GL1 and GASA4, which are markers for early trichome development (Larkin et al., 1993; Kryvych et al., 2008; Marks et al., 2009). Over 50 loss-of-function mutations in Arabidopsis alter trichome cell fate or development (see Marks et al., 2009 and Morohashi and Grotewold, 2009) for recent lists of mutants. "
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ABSTRACT: Transcriptome analysis using the Affymetrix ATH1 platform has been completed on purified trichomes from the gl3-sst mutant. These trichomes display immature features, such as glassy cell walls and blunted branches. The gl3-sst trichome transcriptome was greatly enriched for genes involved in lipid biosynthesis, including those mediating the synthesis of fatty acids and wax. In addition, gl3-sst trichomes displayed reduced expression of the R3 MYBs TRY and CPC, which normally function to limit trichome development. The expression of the MIXTA-like MYB gene NOK was elevated. Members of the MIXTA-like family promote conical cell outgrowth, and in some cases, trichome initiation in diverse plant species. In contrast, NOK limits trichome outgrowth in wild-type Arabidopsis plants. Similar to other MIXTA-like genes, NOK was required for the expansion of gl3-sst trichomes, as the gl3-sst nok double mutant trichomes were greatly reduced in size. Expression of NOK in nok mutants reduced branch formation, whereas in gl3-sst nok, NOK expression promoted trichome cell outgrowth, illustrating duel roles for NOK in both promoting and limiting trichome development. MIXTA-like genes from phylogenetically diverse plant species could substitute for NOK in both nok and gl3-sst nok backgrounds. These findings suggest that certain aspects of NOK and MIXTA-like gene function have been conserved.
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