The Plastomes of Gymnosperms: Evolution toward Reduction, Compaction and Increased Complexity
Gymnosperms are a group of seed-producing plants that include conifers I (the Pinaceae), conifers II (the cupressophytes), cycads, Ginkgo, and gnetophytes (Gnetales). They comprise about 1,100 woody species in 88 genera belonging to 14 families, and are important resources for timbers, resins, and landscape trees. The plastomes (i.e., plastid genomes) of seed plants, are relatively small (ca. 120‒160 Kb in size) and compact (ca. one coding-gene/kb) as compared to their mitochondria and nuclei. Our new data show that the sizes of gymnosperm plastomes vary from 107 to 166 Kb. A common belief is that seed plant plastomes are conserved in organization and size, and that their mutations generally toward loss of genes (or transfers of genes to nuclear genomes) and AT-biased. However, our evolutionary reconstructions and analyses challenge these notions. I will show that the evolution of gymnosperm plastomes is highly dynamic and distinctive, and that the general trend is toward reduction, compaction, and increased complication. I will also discuss the mechanisms that underline these diverse plastomes and propose possible models to interpret the observed trends in different groups.
Dr. Shu-Miaw Chaw
- Distinguished Research Fellow, Biodiversity Research Center, Academia Sinica, Taiwan
- Faculty Member, Taiwan International Graduate Program in Biodiversity (BIODIV)