Insertional mutagenesis in Populus: relevance and feasibility

Abstract

The recent sequencing of the first tree genome, that of the black cottonwood (Populus trichocarpa), opens a new chapter in tree functional genomics. While the completion of the genome is a milestone, mobilizing this significant resource for better understanding the growth and development of woody perennials will be an even greater undertaking in the years to come. In other model organisms, a critical tool for high-throughput analysis of gene function has been the generation of large mutagenized populations. Some mutagenesis technologies and approaches cannot be applied to trees because of their typically outcrossing breeding systems, high heterozygosity, large body size, and delayed flowering. In contrast, gene-tagging approaches that use insertional mutagenesis to create dominant phenotypes are ideally suited for trees and, especially, Populus. Both activation tagging and enhancer trap programs have been successful in identifying new genes important to tree development. The generation of genomewide insertional mutant populations, which provide direct functional links between genes and phenotypes, should help to integrate in silico analyses of gene and protein expression, association studies of natural genetic polymorphism, and phenotypic analyses of adaptation and development.

Ac/Ds-transposon activation tagging in poplar: a powerful tool for gene discovery

“…To date, successful T-DNA-based activation tagging mutagenesis in trees has been reported only for poplar [14,15] and GA2-OXIDASE , a gibberellin catabolism gene, was the first tree gene that was isolated from a poplar T-DNA insertion population comprising 627 individuals [22]. In the following years, other T-DNA activation tagging poplar populations were produced and screened for developmental abnormalities including alterations in leaf and stem structure as well as overall stature by Harrison et al [21] The mutant frequency reported for the largest activation tagging poplar population (with 1,800 independent transgenic lines) was about 2.4%.…”

Eucalyptus applied genomics: from gene sequences to breeding tools

“…Gene tagging through insertional mutagenesis approaches is a particularly appealing method in heterozygous trees that cannot be easily selfed, as it would generate dominant phenotypes. In Eucalyptus , the use of such an approach as a practical tool for genome‐wide gene characterization and breeding faces the same kinds of logistical and biological obstacles as found in Populus , but these might be overcome by large‐scale collaborative efforts (Busov et al ., 2005). To mitigate the biological and biochemical limitations to the study of wood formation in trees using mutant phenotypes, in vitro wood formation systems can be employed to introduce transgenes transiently or stably into growing wood‐producing tissue.…”

Poplar PtabZIP1‐like enhances lateral root formation and biomass growth under drought stress

“…We have previously shown that activation tagging is a powerful forward genetics approach for gene discovery in Populus (Busov et al ., , , ; Yordanov et al ., , ; Trupiano et al ., ). Here, we report the identification and characterization of a poplar activation tagging mutant with increased lateral root (LR) development under high osmotic conditions that typically are prohibitive for LR development.…”