Biomedical subjects

Leonel van Zyl

Publications and source records attributed to Leonel van Zyl.

5 recordsLinked to original sources

PubMed2004

Microarray analyses of gene expression during adventitious root development in Pinus contorta.

In order to investigate the gene expression pattern during adventitious root development, RNA of Pinus contorta hypocotyls, pulse-treated with the auxin indole-3-butyric acid and harvested at distinct developmental time points of root development, was hybridized to microarrays containing 2,178 cDNAs from Pinus taeda. Over the period of observation of root development, the transcript levels of 220 genes changed significantly. During the root initiation phase, genes involved in cell replication and cell wall weakening and a transcript encoding a PINHEAD/ZWILLE-like protein were up-regulated, while genes related to auxin transport, photosynthesis, and cell wall synthesis were down-regulated. In addition, there were changes in transcript abundance of genes related to water stress. During the root meristem formation phase the transcript abundances of genes involved in auxin transport, auxin responsive transcription, and cell wall synthesis, and of a gene encoding a B-box zinc finger-like protein, increased, while those encoding proteins involved in cell wall weakening decreased. Changes of transcript abundance of genes related to water stress during the root meristem formation and root formation phase indicate that the plant roots had become functional in water transport. Simultaneously, genes involved in auxin transport were up-regulated, while genes related to cell wall modification were down-regulated. Finally, during the root elongation phase down-regulation of transcripts encoding proteins involved in cell replication and stress occurred. Based on the observed changes in transcript abundances, we suggest hypotheses about the relative importance of various physiological processes during the auxin-induced development of roots in P. contorta.

Cell Division↗

PubMed2004

The effect of reduced glutathione on morphology and gene expression of white spruce (Picea glauca) somatic embryos.

Inclusions of reduced glutathione (GSH) in the maturation medium increased the conversion frequency of white spruce somatic embryos without the need of a partial drying treatment (PDT). This beneficial effect was the result of major alterations in morphology and gene expression during the maturation period. Compared with control embryos, GSH-treated embryos showed a differential accumulation of storage products, i.e. preferential deposition of starch, the reduced formation of protein bodies, and increased vacuolation of cells. These morphological changes correlated with extensive alterations of gene expression occurring throughout the maturation period. The transcript profiles of stage-specific embryos matured with or without GSH were analysed using a DNA microarray containing 2 178 cDNAs from loblolly pine (Pinus taeda). The efficiency of heterologous hybridization between spruce and pine species on microarrays has previously been documented. The results indicate that several genes involved in a variety of signal regulatory pathways were differentially expressed in developing GSH- treated embryos. The transcript levels of many genes involved in carbohydrate metabolism and protein synthesis were altered by the presence of GSH and denoted differences in physiology between treatments. Extensive changes in the expression of genes participating in hormone synthesis, nucleotide metabolism, and meristem formation were also observed and related to the post-embryonic performance of the embryos.

Desiccation↗

PubMed2003

Up, down and up again is a signature global gene expression pattern at the beginning of gymnosperm embryogenesis.

Somatic embryogenesis of a gymnosperm, Picea abies, represents a sequence of specifically regulated developmental stages including proembryogenic mass (PEM), PEM-to-embryo transition, and early and late embryogeny. Here, we report cDNA array analysis of expression patterns of 373 genes in the beginning of P. abies embryo development. The analysis revealed a group of 107 genes (29% of arrayed cDNAs) which were upregulated upon PEM-to-embryo transition, then downregulated during early embryogeny and finally upregulated again at the beginning of late embryogeny. This major gene expression pattern was abrogated in a developmentally arrested cell line that is unable to pass through the PEM-to-embryo transition. Thirty-five genes (9.4% of arrayed cDNAs) were found to be differentially expressed during normal embryonic pattern formation. Among them, 22 genes (5.9% of arrayed cDNAs) were directly associated with embryo pattern formation and can be considered as marker genes for early stages of P. abies embryogenesis. The majority of the marker genes encode for proteins involved in translation and posttranslational modification. Among them, 18 genes displayed the major expression pattern.

Gene Expression↗

PubMed2003

The effects of polyethylene glycol on gene expression of developing white spruce somatic embryos.

Somatic embryogenic cultures of white spruce (Picea glauca) represent a valuable system to study molecular mechanisms regulating embryo development because many embryos of defined developmental stages can be generated. The inclusion of polyethylene glycol (PEG) in the maturation medium can improve the number and quality of embryos produced. To learn more about the mechanism of action of PEG, we analyzed transcript profiles of stage-specific embryos matured without (control) or with (PEG treated) PEG. RNA extracted from maturing spruce embryos was analyzed on DNA microarrays containing 2,178 cDNAs from loblolly pine (Pinus taeda). The efficiency of heterologous hybridization between spruce and pine species on microarrays has been documented previously (L. van Zyl, S. von Arnold, P. Bozhkov, Y. Chen, U. Egertsdotter, J. MacKay, R. Sederoff, J. Shen, L. Zelena, D. Clapham [2002] Comp Funct Genomics 3: 306-318). Several pine genes, including the apparent homologs to the Arabidopsis genes ZWILLE, FIDDLEHEAD, FUSCA, and SCARECROW, increased in expression after PEG treatments. These genes are known to be involved in the formation of the embryo body plan and in the control of the shoot and root apical meristems. The increased transcript levels of these genes in immature PEG-treated embryos suggest that PEG may improve the quality of spruce somatic embryos by promoting normal differentiation of the embryonic shoot and root. Changes in the transcript levels of many genes involved in sucrose catabolism and nitrogen assimilation and utilization were also observed between control and PEG-treated embryos.

Arabidopsis Proteins↗

PubMed2003

Photosynthetic acclimation is reflected in specific patterns of gene expression in drought-stressed loblolly pine.

Because the product of a single gene can influence many aspects of plant growth and development, it is necessary to understand how gene products act in concert and upon each other to effect adaptive changes to stressful conditions. We conducted experiments to improve our understanding of the responses of loblolly pine (Pinus taeda) to drought stress. Water was withheld from rooted plantlets of to a measured water potential of -1 MPa for mild stress and -1.5 MPa for severe stress. Net photosynthesis was measured for each level of stress. RNA was isolated from needles and used in hybridizations against a microarray consisting of 2173 cDNA clones from five pine expressed sequence tag libraries. Gene expression was estimated using a two-stage mixed linear model. Subsequently, data mining via inductive logic programming identified rules (relationships) among gene expression, treatments, and functional categories. Changes in RNA transcript profiles of loblolly pine due to drought stress were correlated with physiological data reflecting photosynthetic acclimation to mild stress or photosynthetic failure during severe stress. Analysis of transcript profiles indicated that there are distinct patterns of expression related to the two levels of stress. Genes encoding heat shock proteins, late embryogenic-abundant proteins, enzymes from the aromatic acid and flavonoid biosynthetic pathways, and from carbon metabolism showed distinctive responses associated with acclimation. Five genes shown to have different transcript levels in response to either mild or severe stress were chosen for further analysis using real-time polymerase chain reaction. The real-time polymerase chain reaction results were in good agreement with those obtained on microarrays.

Acclimatization↗