Abstract
Conifers, Ginkgo, cycads and gnetophytes comprise the four groups of extant gymnosperms holding a unique position of sharing common ancestry with the angiosperms. Comparative studies of gymnosperms and angiosperms are the key to a better understanding of ancient seed plant morphologies, how they have shifted over evolution to shape modern day species, and how the genes governing these morphologies have evolved. However, conifers and other gymnosperms have been notoriously difficult to study due to their long generation times, inaccessibility to genetic experimentation and unavailable genome sequences. Now, with three draft genomes from spruces and pines, rapid advances in next generation sequencing methods for genome wide expression analyses, and enhanced methods for genetic transformation, we are much better equipped to address a number of key evolutionary questions relating to seed plant evolution. In this mini-review we highlight recent progress in conifer developmental biology relevant to evo-devo questions. We discuss how genome sequence data and novel techniques might allow us to explore genetic variation and naturally occurring conifer mutants, approaches to reduce long generation times to allow for genetic studies in conifers, and other potential upcoming research avenues utilizing current and emergent techniques. Results from developmental studies of conifers and other gymnosperms in comparison to those in angiosperms will provide information to trace core molecular developmental control tool kits of ancestral seed plants, but foremost they will greatly improve our understanding of the biology of conifers and other gymnosperms in their own right.
Highlights
Reviewed by: Lydia Gramzow, Friedrich-Schiller-University Jena, Germany Francisco Vergara-Silva, Universidad Nacional Autónoma de México, Mexico Giorgio Casadoro, University of Padova, Italy
Comparative studies of gymnosperms and angiosperms are the key to a better understanding of ancient seed plant morphologies, how they have shifted over evolution to shape modern day species, and how the genes governing these morphologies have evolved
With three draft genomes from spruces and pines, rapid advances in generation sequencing methods for genome wide expression analyses, and enhanced methods for genetic transformation, we are much better equipped to address a number of key evolutionary questions relating to seed plant evolution
Summary
Conifers are of great ecological and economic importance; they dominate the forests of the northern hemisphere, and comprise two thirds of extant gymnosperms (Wang and Ran, 2014). The development of next-generation sequencing (NGS) techniques has surfaced as one of the most important technological breakthrough in current biology (Wang et al, 2009), making genomes and transcriptomes available from both model and non-model species. Functional studies are crucial to test hypotheses of biochemical activity and forward genetic screens have been imperative in identifying novel key developmental regulators in angiosperms This relied on mapping using recombinant mapping populations, but NGS allows sequencing of entire genomes, dramatically speeding up cloning of the causal mutation in model systems, and potentially making forward genetic screens possible in non-model systems (Schneeberger, 2014). In species with long life cycles such as gymnosperms genetic transformation over seed generations is not possible This can be circumvented by utilizing somatic embryogenesis, in which proliferating embryogenic tissue is transformed by direct DNA delivery or via bacteria-mediated horizontal gene transfer. The use of embryo explants during transformation, followed by selective tissue culture and plant regeneration, provide an alternative for recalcitrant species (Tang et al, 2014)
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