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Columnar apple primary roots share some features of the columnar-specific gene expression profile of aerial plant parts as evidenced by RNA-Seq analysis.

Petersen R, Djozgic H, Rieger B, Rapp S, Schmidt ER - BMC Plant Biol. (2015)

Bottom Line: Radicles mainly express genes associated with primary metabolism, growth and development.Homozygous columnar embryos are viable and form normal radicles under natural conditions, and selection towards heterozygous plants most likely occurs due to breeders' preferences.Cell wall and phytohormone biosynthesis and metabolism experience differential regulation in columnar radicles.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics, Johannes Gutenberg-University, Mainz, D-55128, Germany. peterser@uni-mainz.de.

ABSTRACT

Background: Primary roots (radicles) represent the first visible developmental stages of the plant and are crucial for nutrient supply and the integration of environmental signals. Few studies have analyzed primary roots at a molecular level, and were mostly limited to Arabidopsis. Here we study the primary root transcriptomes of standard type, heterozygous columnar and homozygous columnar apple (Malus x domestica) by RNA-Seq and quantitative real-time PCR. The columnar growth habit is characterized by a stunted main axis and the development of short fruit spurs instead of long lateral branches. This compact growth possesses economic potential because it allows high density planting and mechanical harvesting of the trees. Its molecular basis has been identified as a nested Gypsy-44 retrotransposon insertion; however the link between the insertion and the phenotype as well as the timing of the phenotype emergence are as yet unclear. We extend the transcriptomic studies of columnar tissues to the radicles, which are the earliest developmental stage and investigate whether homozygous columnar seedlings are viable.

Results: Radicles mainly express genes associated with primary metabolism, growth and development. About 200 genes show differential regulation in a comparison of heterozygous columnar radicles with non-columnar radicles, whereas the comparison of homozygous columnar radicles with non-columnar radicles yields about 300 differentially regulated genes. Genes involved in cellulose and phenylpropanoid biosynthesis, cell wall modification, transcription and translation, ethylene and jasmonate biosynthesis are upregulated in columnar radicles. Genes in the vicinity of the columnar-specific Gypsy-44 insertion experience an especially strong differential regulation: the direct downstream neighbor, dmr6-like, is downregulated in heterozygous columnar radicles, but strongly upregulated in columnar shoot apical meristems.

Conclusions: The transcriptomic profile of primary roots reflects their pivotal role in growth and development. Homozygous columnar embryos are viable and form normal radicles under natural conditions, and selection towards heterozygous plants most likely occurs due to breeders' preferences. Cell wall and phytohormone biosynthesis and metabolism experience differential regulation in columnar radicles. Presumably the first step of the differential regulation most likely happens within the region of the retrotransposon insertion and its tissue-specificity suggests involvement of one (or several) tissue-specific regulator(s).

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Venn diagram summarizing the differentially expressed genes identified in the three binary comparative gene expression analyses. While no genes were found to be differentially expressed across all three analyses, there was a high degree of overlap of the genes detected as differentially expressed in either columnar genotype versus the non-columnar genotype.
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Fig4: Venn diagram summarizing the differentially expressed genes identified in the three binary comparative gene expression analyses. While no genes were found to be differentially expressed across all three analyses, there was a high degree of overlap of the genes detected as differentially expressed in either columnar genotype versus the non-columnar genotype.

Mentions: The differentially expressed genes identified in each of the three binary analyses were compared among each other (FigureĀ 4). No genes were identified as differentially expressed in all three comparisons. 80 of the genes showing differences in gene expression between heterozygous and non-columnar radicles also show differential expression in homozygous columnar compared with non-columnar radicles. 30 of the genes identified as differentially expressed in the heterozygous columnar versus the non-columnar radicles were also differentially expressed in the heterozygous versus the homozygous columnar radicles. Another 39 genes differentially expressed in the heterozygous versus the homozygous columnar radicles were also differentially expressed in the homozygous columnar versus non-columnar radicles.Figure 4


Columnar apple primary roots share some features of the columnar-specific gene expression profile of aerial plant parts as evidenced by RNA-Seq analysis.

Petersen R, Djozgic H, Rieger B, Rapp S, Schmidt ER - BMC Plant Biol. (2015)

Venn diagram summarizing the differentially expressed genes identified in the three binary comparative gene expression analyses. While no genes were found to be differentially expressed across all three analyses, there was a high degree of overlap of the genes detected as differentially expressed in either columnar genotype versus the non-columnar genotype.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4352258&req=5

Fig4: Venn diagram summarizing the differentially expressed genes identified in the three binary comparative gene expression analyses. While no genes were found to be differentially expressed across all three analyses, there was a high degree of overlap of the genes detected as differentially expressed in either columnar genotype versus the non-columnar genotype.
Mentions: The differentially expressed genes identified in each of the three binary analyses were compared among each other (FigureĀ 4). No genes were identified as differentially expressed in all three comparisons. 80 of the genes showing differences in gene expression between heterozygous and non-columnar radicles also show differential expression in homozygous columnar compared with non-columnar radicles. 30 of the genes identified as differentially expressed in the heterozygous columnar versus the non-columnar radicles were also differentially expressed in the heterozygous versus the homozygous columnar radicles. Another 39 genes differentially expressed in the heterozygous versus the homozygous columnar radicles were also differentially expressed in the homozygous columnar versus non-columnar radicles.Figure 4

Bottom Line: Radicles mainly express genes associated with primary metabolism, growth and development.Homozygous columnar embryos are viable and form normal radicles under natural conditions, and selection towards heterozygous plants most likely occurs due to breeders' preferences.Cell wall and phytohormone biosynthesis and metabolism experience differential regulation in columnar radicles.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics, Johannes Gutenberg-University, Mainz, D-55128, Germany. peterser@uni-mainz.de.

ABSTRACT

Background: Primary roots (radicles) represent the first visible developmental stages of the plant and are crucial for nutrient supply and the integration of environmental signals. Few studies have analyzed primary roots at a molecular level, and were mostly limited to Arabidopsis. Here we study the primary root transcriptomes of standard type, heterozygous columnar and homozygous columnar apple (Malus x domestica) by RNA-Seq and quantitative real-time PCR. The columnar growth habit is characterized by a stunted main axis and the development of short fruit spurs instead of long lateral branches. This compact growth possesses economic potential because it allows high density planting and mechanical harvesting of the trees. Its molecular basis has been identified as a nested Gypsy-44 retrotransposon insertion; however the link between the insertion and the phenotype as well as the timing of the phenotype emergence are as yet unclear. We extend the transcriptomic studies of columnar tissues to the radicles, which are the earliest developmental stage and investigate whether homozygous columnar seedlings are viable.

Results: Radicles mainly express genes associated with primary metabolism, growth and development. About 200 genes show differential regulation in a comparison of heterozygous columnar radicles with non-columnar radicles, whereas the comparison of homozygous columnar radicles with non-columnar radicles yields about 300 differentially regulated genes. Genes involved in cellulose and phenylpropanoid biosynthesis, cell wall modification, transcription and translation, ethylene and jasmonate biosynthesis are upregulated in columnar radicles. Genes in the vicinity of the columnar-specific Gypsy-44 insertion experience an especially strong differential regulation: the direct downstream neighbor, dmr6-like, is downregulated in heterozygous columnar radicles, but strongly upregulated in columnar shoot apical meristems.

Conclusions: The transcriptomic profile of primary roots reflects their pivotal role in growth and development. Homozygous columnar embryos are viable and form normal radicles under natural conditions, and selection towards heterozygous plants most likely occurs due to breeders' preferences. Cell wall and phytohormone biosynthesis and metabolism experience differential regulation in columnar radicles. Presumably the first step of the differential regulation most likely happens within the region of the retrotransposon insertion and its tissue-specificity suggests involvement of one (or several) tissue-specific regulator(s).

Show MeSH