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Profiling expression changes caused by a segmental aneuploid in maize.

Makarevitch I, Phillips RL, Springer NM - BMC Genomics (2008)

Bottom Line: Maize plants that are trisomic for 90% of the short arm of chromosome 5 and monosomic for a small distal portion of the short arm of chromosome 6 exhibited a phenotypic syndrome that includes reduced stature, tassel morphology changes and the presence of knots on the leaves.Expression profiling revealed that approximately 40% of the expressed genes in the trisomic region exhibited the expected 1.5 fold increased transcript levels while the remaining 60% of genes did not show altered expression even with increased gene dosage.We found that the majority of genes with altered expression levels were located within the chromosomal regions affected by the segmental aneuploidy and exhibits dosage-dependent expression changes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, St, Paul MN 55108, USA. springer@umn.edu.

ABSTRACT

Background: While changes in chromosome number that result in aneuploidy are associated with phenotypic consequences such as Down syndrome and cancer, the molecular causes of specific phenotypes and genome-wide expression changes that occur in aneuploids are still being elucidated.

Results: We employed a segmental aneuploid condition in maize to study phenotypic and gene expression changes associated with aneuploidy. Maize plants that are trisomic for 90% of the short arm of chromosome 5 and monosomic for a small distal portion of the short arm of chromosome 6 exhibited a phenotypic syndrome that includes reduced stature, tassel morphology changes and the presence of knots on the leaves. The knotted-like homeobox gene knox10, which is located on the short arm of chromosome 5, was shown to be ectopically expressed in developing leaves of the aneuploid plants. Expression profiling revealed that approximately 40% of the expressed genes in the trisomic region exhibited the expected 1.5 fold increased transcript levels while the remaining 60% of genes did not show altered expression even with increased gene dosage.

Conclusion: We found that the majority of genes with altered expression levels were located within the chromosomal regions affected by the segmental aneuploidy and exhibits dosage-dependent expression changes. A small number of genes exhibit higher levels of expression change not predicted by the dosage, or display altered expression even though they are not located in the aneuploid regions.

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Phenotypic effects of DpDf segmental aneuploidy in maize. (A) DpDf plants are smaller and are ca. 2 weeks behind in development. (B) DpDf plants display partially necrotic tassels that are shorter and have fewer branches. The main rachis of the tassel tends to be thicker than in wild-type siblings. (C-E) show views of the knots that form on the leaves of DpDf plants. The adaxial surface of the leaf blade (C) shows ectopic ligule formation near the midrib while the abaxial surface (D and E) display knot-like protrusions.
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Figure 2: Phenotypic effects of DpDf segmental aneuploidy in maize. (A) DpDf plants are smaller and are ca. 2 weeks behind in development. (B) DpDf plants display partially necrotic tassels that are shorter and have fewer branches. The main rachis of the tassel tends to be thicker than in wild-type siblings. (C-E) show views of the knots that form on the leaves of DpDf plants. The adaxial surface of the leaf blade (C) shows ectopic ligule formation near the midrib while the abaxial surface (D and E) display knot-like protrusions.

Mentions: Adjacent I disjunction of a plant that is heterozygous for T5-6b (Figure 1) can result in the production of a viable duplicate-deficient (DpDf) gamete. This gamete, which has a duplication for the majority of the short arm of chromosome 5 and is deficient for a small region of chromosome 6, is female transmissible but can not be transmitted through the male parent [17]. The fertilization of this female DpDf gamete by a normal male gamete results in the production of a plant with segmental aneuploidy. These plants contain three copies of the majority of the short arm of chromosome 5 and only one copy of a small portion of the short arm of chromosome 6 (Figure 1) and are referred herein as DpDf. The DpDf plants display a phenotypic syndrome that includes leaf knotting, partial tassel sterility, late flowering time and overall changes in the plant architecture (Figure 2, Table 1). DpDf plants are shorter than their wild-type siblings and have smaller stalk diameter (Table 1). The flowering time of DpDf plants is delayed 8–13 days relative to their wild-type siblings. The tassels of DpDf plants are shorter and thicker compared to wild-type siblings and have a smaller number of branches. Notably, the tassels of DpDf plants are partially necrotic and produce many branches with few to no developed florets (Figure 2, Table 1). The phenotypic syndrome of DpDf plants is more severe in DpDf plants produced from self-pollinated DpDfs (Table 1) than in the first generation DpDf plants, suggesting the accumulation of phenotypic effects when the segmental aneuploid condition is maintained for multiple generations. To understand the molecular basis of the other phenotypic alterations in the DpDf plants, we used a more comprehensive approach and looked at changes in gene transcription levels caused by segmental aneuploidy.


Profiling expression changes caused by a segmental aneuploid in maize.

Makarevitch I, Phillips RL, Springer NM - BMC Genomics (2008)

Phenotypic effects of DpDf segmental aneuploidy in maize. (A) DpDf plants are smaller and are ca. 2 weeks behind in development. (B) DpDf plants display partially necrotic tassels that are shorter and have fewer branches. The main rachis of the tassel tends to be thicker than in wild-type siblings. (C-E) show views of the knots that form on the leaves of DpDf plants. The adaxial surface of the leaf blade (C) shows ectopic ligule formation near the midrib while the abaxial surface (D and E) display knot-like protrusions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2254597&req=5

Figure 2: Phenotypic effects of DpDf segmental aneuploidy in maize. (A) DpDf plants are smaller and are ca. 2 weeks behind in development. (B) DpDf plants display partially necrotic tassels that are shorter and have fewer branches. The main rachis of the tassel tends to be thicker than in wild-type siblings. (C-E) show views of the knots that form on the leaves of DpDf plants. The adaxial surface of the leaf blade (C) shows ectopic ligule formation near the midrib while the abaxial surface (D and E) display knot-like protrusions.
Mentions: Adjacent I disjunction of a plant that is heterozygous for T5-6b (Figure 1) can result in the production of a viable duplicate-deficient (DpDf) gamete. This gamete, which has a duplication for the majority of the short arm of chromosome 5 and is deficient for a small region of chromosome 6, is female transmissible but can not be transmitted through the male parent [17]. The fertilization of this female DpDf gamete by a normal male gamete results in the production of a plant with segmental aneuploidy. These plants contain three copies of the majority of the short arm of chromosome 5 and only one copy of a small portion of the short arm of chromosome 6 (Figure 1) and are referred herein as DpDf. The DpDf plants display a phenotypic syndrome that includes leaf knotting, partial tassel sterility, late flowering time and overall changes in the plant architecture (Figure 2, Table 1). DpDf plants are shorter than their wild-type siblings and have smaller stalk diameter (Table 1). The flowering time of DpDf plants is delayed 8–13 days relative to their wild-type siblings. The tassels of DpDf plants are shorter and thicker compared to wild-type siblings and have a smaller number of branches. Notably, the tassels of DpDf plants are partially necrotic and produce many branches with few to no developed florets (Figure 2, Table 1). The phenotypic syndrome of DpDf plants is more severe in DpDf plants produced from self-pollinated DpDfs (Table 1) than in the first generation DpDf plants, suggesting the accumulation of phenotypic effects when the segmental aneuploid condition is maintained for multiple generations. To understand the molecular basis of the other phenotypic alterations in the DpDf plants, we used a more comprehensive approach and looked at changes in gene transcription levels caused by segmental aneuploidy.

Bottom Line: Maize plants that are trisomic for 90% of the short arm of chromosome 5 and monosomic for a small distal portion of the short arm of chromosome 6 exhibited a phenotypic syndrome that includes reduced stature, tassel morphology changes and the presence of knots on the leaves.Expression profiling revealed that approximately 40% of the expressed genes in the trisomic region exhibited the expected 1.5 fold increased transcript levels while the remaining 60% of genes did not show altered expression even with increased gene dosage.We found that the majority of genes with altered expression levels were located within the chromosomal regions affected by the segmental aneuploidy and exhibits dosage-dependent expression changes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, St, Paul MN 55108, USA. springer@umn.edu.

ABSTRACT

Background: While changes in chromosome number that result in aneuploidy are associated with phenotypic consequences such as Down syndrome and cancer, the molecular causes of specific phenotypes and genome-wide expression changes that occur in aneuploids are still being elucidated.

Results: We employed a segmental aneuploid condition in maize to study phenotypic and gene expression changes associated with aneuploidy. Maize plants that are trisomic for 90% of the short arm of chromosome 5 and monosomic for a small distal portion of the short arm of chromosome 6 exhibited a phenotypic syndrome that includes reduced stature, tassel morphology changes and the presence of knots on the leaves. The knotted-like homeobox gene knox10, which is located on the short arm of chromosome 5, was shown to be ectopically expressed in developing leaves of the aneuploid plants. Expression profiling revealed that approximately 40% of the expressed genes in the trisomic region exhibited the expected 1.5 fold increased transcript levels while the remaining 60% of genes did not show altered expression even with increased gene dosage.

Conclusion: We found that the majority of genes with altered expression levels were located within the chromosomal regions affected by the segmental aneuploidy and exhibits dosage-dependent expression changes. A small number of genes exhibit higher levels of expression change not predicted by the dosage, or display altered expression even though they are not located in the aneuploid regions.

Show MeSH
Related in: MedlinePlus