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Abstract Detail



A Broader view for Plant EvoDevo: novel approaches for diverse model systems

Sakakibara, Keiko [1].

Evolution of the alternation of generation in Land Plants.

Land plants undergo an alternation of generations, producing multicellular bodies in both haploid (1n: gametophyte) and diploid (2n: sporophyte) generations. Plant body plan in each generation is regulated by distinct developmental programs initiated at meiosis and fertilization, respectively. In mosses, the haploid gametophyte generation is dominant, whereas in vascular plants—including ferns, gymnosperms, and angiosperms—the diploid sporophyte generation is dominant. Land plants evolved from freshwater algal ancestors, with a life cycle similar to extant charophycean algae, the algal taxa most closely related to land plants. These algae have multicellular haploid bodies that produce gametes, and after fertilization, the diploid zygote directly undergoes meiosis to produce haploid spores. The multicellular diploid sporophyte generation of land plants is thought to have evolved through a delay in meiosis, with extensive mitotic cell divisions between the formation of the zygote and the production of spores via meiosis.
KNOTTED1-LIKE HOMEOBOX (KNOX) genes are transcription factors identified in green plants and separated into two subfamilies in land plants, KNOX1 and KNOX2, resulting from a gene duplication in the lineage leading to land plants. KNOX1 genes are well-known regulators of sporophytic (diploid) meristematic genes, but the functions of KNOX2 genes were unknown until a recent discovery. Deletion of the KNOX2 in the moss Physcomitrella patens resulted in the development of gametophyte bodies from diploid embryos without meiosis. Thus, KNOX2 acts to prevent the haploid-specific body plan from developing in the diploid plant body, indicating a critical role for the evolution of KNOX2 in establishing the alternation of generations in land plants. KNOX1/KNOX2 duplication facilitated the evolution of more complex gene regulatory networks to perform two critical roles in the diploid phase of the alternation of generations and was instrumental in the establishment of a multicellular diploid generation in land plants.


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1 - Kanazawa University, Advanced Science Research Center, Takara-machi 13-1, Kanazawa-shi, Ishikawa, 920-0934, Japan

Keywords:
alternation of generations.

Presentation Type: Symposium Presentation
Session: SY02
Location: Salon 11/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 8:45 AM
Number: SY02003
Abstract ID:545
Candidate for Awards:None


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