In plants, genome duplication followed by genome diversification and selection is recognized as a major evolutionary process. Rapid epigenetic and genetic changes that affect the transcription of parental genes are frequently observed after polyploidization. The pattern of alternative splicing is also frequently altered, yet the related molecular processes remain largely unresolved. Here, we study the inheritance and expression of parental variants of three floral organ identity genes in allotetraploid tobacco. DEFICIENS and GLOBOSA are B-class genes, and AGAMOUS is a C-class gene. Parental variants of these genes were found to be maintained in the tobacco genome, and the respective mRNAs were present in flower buds in comparable amounts. However, among five tobacco cultivars, we identified two in which the majority of paternal GLOBOSA pre-mRNA transcripts undergo exon 3 skipping, producing an mRNA with a premature termination codon. At the DNA level, we identified a G-A transition at the very last position of exon 3 in both cultivars. Although alternative splicing resulted in a dramatic decrease in full-length paternal GLOBOSA mRNA, no phenotypic effect was observed. Our finding likely serves as an example of the initiation of homoeolog diversification in a relatively young polyploid genome.

• Keywords
• Alternative splicing, Floral genes, Flowering, Polyploidy, Tobacco,
• MeSH
• Alternative Splicing genetics   MeSH
• Point Mutation genetics   MeSH
• Exons genetics   MeSH
• Transcription, Genetic * MeSH
• Homeodomain Proteins biosynthesis   genetics   MeSH
• Nucleotides genetics   MeSH
• Polyploidy MeSH
• RNA Precursors genetics   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Proteins biosynthesis   genetics   MeSH
• Nicotiana genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• GLOBOSA protein, plant MeSH Browser
• Homeodomain Proteins MeSH
• Nucleotides MeSH
• RNA Precursors MeSH
• Plant Proteins MeSH

Developmental processes are closely connected to certain states of epigenetic information which, among others, rely on methylation of chromatin. S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are key cofactors of enzymes catalyzing DNA and histone methylation. To study the consequences of altered SAH/SAM levels on plant development we applied 9-(S)-(2,3-dihydroxypropyl)-adenine (DHPA), an inhibitor of SAH-hydrolase, on tobacco seeds during a short phase of germination period (6 days). The transient drug treatment induced: (1) dosage-dependent global DNA hypomethylation mitotically transmitted to adult plants; (2) pleiotropic developmental defects including decreased apical dominance, altered leaf and flower symmetry, flower whorl malformations and reduced fertility; (3) dramatic upregulation of floral organ identity genes NTDEF, NTGLO and NAG1 in leaves. We conclude that temporal SAH-hydrolase inhibition deregulated floral genes expression probably via chromatin methylation changes. The data further show that plants might be particularly sensitive to accurate setting of SAH/SAM levels during critical developmental periods.

• MeSH
• Adenine analogs & derivatives   toxicity   MeSH
• Adenosylhomocysteinase antagonists & inhibitors   metabolism   MeSH
• DNA Primers genetics   MeSH
• Epigenesis, Genetic drug effects   physiology   MeSH
• Germination drug effects   physiology   MeSH
• DNA, Complementary genetics   MeSH
• Flowers anatomy & histology   physiology   MeSH
• DNA Methylation MeSH
• Statistics, Nonparametric MeSH
• Pollen physiology   MeSH
• Gene Expression Regulation, Plant drug effects   genetics   physiology   MeSH
• Plant Proteins metabolism   MeSH
• Blotting, Southern MeSH
• Nicotiana enzymology   physiology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 9-(2,3-dihydroxypropyl)adenine MeSH Browser
• Adenine MeSH
• Adenosylhomocysteinase MeSH
• DNA Primers MeSH
• GLO protein, Nicotiana tabacum MeSH Browser
• DNA, Complementary MeSH
• Plant Proteins MeSH