Canadian Forest Service Publications
Overexpression of CYCD1;2 in activation-tagged Populus tremula x Populus alba results in decreased cell size and altered leaf morphology. 2015. Williams, M.; Lowndes, L.; Regan, S.; Beardmore, T. Tree Genetics & Genomes 11: 66.
Issued by: Atlantic Forestry Centre
Catalog ID: 36304
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This paper includes the characterization of an activation-tagged mutant named rippled leaf that displays distinctive rippled-leaf morphology. Gene expression and microscopic analysis were done to characterize the rippled leaf mutant, and transgenic overexpression lines were generated and characterized using these methods. The rippled leaf mutant was found to have an activated CYCLIN D1 (CYCD1;2), and overexpression of the gene using the 35S CaMV promoter resulted in plants with a highly similar leaf morphology. Microscopic analysis of the midvein of rippled leaf mutant revealed that the mutant possessed significantly smaller and more numerous cortical parenchyma cells in its midvein compared with wild type. As well, in rippled leaf, the vascular tissue represented a larger proportion of the midvein.In transgenic lines, there was a similar change in cortical cell size, and an even larger proportion of the midvein was vascular tissue. In conclusion, a mutant with a leaf alteration phenotype was characterized. The CYCD1;2 gene was found to be responsible for this phenotype, and the phenotype was recapitulated using overexpression of transgenic lines. Further studies with mutants such as rippled leaf are necessary for a better understanding of cell division and its relationship to plant growth and development.
Plain Language Summary
In the last decade or so, decreasing costs associated with genome sequencing have enabled the launch of multiple different projects to identify new genes and their functions within organisms. Among these functional genomics projects, activation tagging is a powerful approach that creates plant mutants having different genes overexpressed due to the enhancer-containing tag being randomly inserted in the genome. These overexpressed genes can alter the phenotype of the plants depending on their function. This paper is about a mutant poplar plant that we have characterized, named rippled leaf, that has wavy leaves and leaf stems. We linked this undulating phenotype to a cyclin D gene (CYCD1;2). Our findings show that an increase in expression of CYCD1:2 is responsible for increasing the number of cells in the midvein of the leaves and that the midvein of the mutant has a larger vasculature to cortex ratio. Because this gene is involved in cell cycle regulation, information about its function could improve our understanding of the basic mechanisms that control the cell cycle, particularly in trees. This information is necessary in order to understand many basic questions, such as whether cell division drives growth and development, or whether they simply follow a pre-established developmental plan.