Canadian Forest Service Publications
Heterologous over-expression of ACCSYNTHASE8 (ACS8) in Populus tremula x P. albaclone 717-1B4 results in elevated levels of ethylene and induces stem dwarfism and reduced leaf size through separate genetic pathways. 2014. Plett, J.M.; Williams, M.; LeClair, G.; Regan, S.; Beardmore, T. Frontiers in Plant Science 5: 514
Issued by: Atlantic Forestry Centre
Catalog ID: 36377
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Plant height is an important agronomic and horticultural trait that impacts plant productivity, durability and esthetic appeal. A number of the plant hormones such as gibberellic acid (GA), auxin and ethylene have been linked to control of plant architecture and size. Reduction in GA synthesis and auxin transport result in dwarfism while ethylene may have a permissive or repressive effect on tissue growth depending upon the age of plant tissues or the environmental conditions considered. We describe here an activation-tagged mutant of Populus tremula x P. alba clone 717-1B4 identified from 2000 independent transgenic lines due to its significantly reduced growth rate and smaller leaf size. Named dwarfy, the phenotype is due to increased expression of PtaACC SYNTHASE8, which codes for an enzyme in the first committed step in the biosynthesis of ethylene. Stems of dwarfy contain fiber and vessel elements that are reduced in length while leaves contain fewer cells. These morphological differences are linked to PtaACS8 inducing different transcriptomic programs in the stem and leaf, with genes related to auxin diffusion and sensing being repressed in the stem and genes related to cell division found to be repressed in the leaves. Altogether, our study gives mechanistic insight into the genetics underpinning ethylene-induced dwarfism in a perennial model organism.
Plain Language Summary
In the last decade or so, the exponential decrease in cost associated to genome sequencing has enabled multiple different projects for the identification of novel genes and their functions within organisms. Among these functional genomics projects, activation tagging is a powerful approach which creates plant mutants that will have different genes being overexpressed due to the enhancer containing tag being randomly inserted in the genome. These overexpressed genes have the potential to alter the phenotype of the plants depending on their function. This paper is about one of those mutant poplar plants that we have characterized named dwarfy that has a reduced growth rate and smaller leaf size phenotype. We were able to link this phenotype to an ACC synthase gene (ACS8), which is involved in the biosynthesis of ethylene, a well-known plant hormone involved in the regulation of many plant development processes. Our findings showed that an increase in expression of ACS8 is responsible for decreasing the number of cells in leaves and that stems of dwarfy contain fiber and vessel elements that are reduced in length. These morphological differences are linked to ACS8 which alters genes related to auxin and cell division. Altogether, our study gives mechanistic insight into the genetics underpinning ethylene-induced dwarfism in a perennial model organism.