Evolution in the Cycles of Life.
The life cycles of eukaryotes alternate between haploid and diploid phases, which are initiated by meiosis and gamete fusion, respectively. In both ascomycete and basidiomycete fungi and chlorophyte algae, the haploid-to-diploid transition is regulated by a pair of paralogous homeodomain protein encoding genes. That a common genetic program controls the haploid-to-diploid transition in phylogenetically disparate eukaryotic lineages suggests this may be the ancestral function for homeodomain proteins. Multicellularity has evolved independently in many eukaryotic lineages in either one or both phases of the life cycle. Organisms, such as land plants, exhibiting a life cycle whereby multicellular bodies develop in both the haploid and diploid phases are often referred to as possessing an alternation of generations. We review recent progress on understanding the genetic basis for the land plant alternation of generations and highlight the roles that homeodomain-encoding genes may have played in the evolution of complex multicellularity in this lineage.
School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia; email: john.bowman@monash.edu.|Department of Plant Biology, University of California, Davis, California 95616.
John L
JL
Bowman
School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia; email: john.bowman@monash.edu.|Department of Life Science, College of Science, Rikkyo University, Tokyo 171-8501, Japan.
Keiko
K
Sakakibara
School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia; email: john.bowman@monash.edu.
Chihiro
C
Furumizu
School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia; email: john.bowman@monash.edu.
Tom
T
Dierschke
D005075:Biological Evolution; D044002:Bryophyta / Q000235:genetics; D000460:Chlorophyta / Q000235:genetics; D004171:Diploidy; D056890:Eukaryota; D005658:Fungi / Q000235:genetics; D006238:Haploidy; D018398:Homeodomain Proteins / Q000235:genetics; D019684:Magnoliopsida / Q000235:genetics; D000459:Phaeophyceae / Q000235:genetics; D010802:Phylogeny; D010944:Plants / Q000235:genetics*; D000461:Rhodophyta / Q000235:genetics
D018398:Homeodomain Proteins
TALE homeodomain; alternation of generations; apogamy; apospory; land plant evolution; multicellularity