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Morphological changes of giant mitochondria in the unicellular to multicellular phase during parthenogenesis of Ulva partita (Ulvophyceae) revealed by expression of mitochondrial targeting GFP and PEG transformation
Author(s) -
Suzuki Ryogo,
Ota Shuhei,
Yamazaki Tomokazu,
Toyoda Atsushi,
aka Satoko,
Matsukura Chiaki,
Kuwano Kazuyoshi,
Kawano Shigeyuki
Publication year - 2016
Publication title -
phycological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.438
H-Index - 44
eISSN - 1440-1835
pISSN - 1322-0829
DOI - 10.1111/pre.12132
Subject(s) - biology , mitochondrion , green fluorescent protein , microbiology and biotechnology , botany , genetics , gene
SUMMARY A giant mitochondrion that branches and connects as a single mitochondrion in a cell has been observed during specific phases of the cell cycle of unicellular green algae, but has not been observed in multicellular algae. The genus Ulva is a green macroalga in which the haploid and diploid phases are isomorphic and its gametes develop parthenogenetically. The existence or absence of the giant mitochondrion, and its behavior in Ulva partita , were investigated using a parthenogenesis system. To observe the parthenogenesis of gametes and the dynamics of mitochondria by fluorescence microscopy, we developed an experimental system for culturing and observing U . partita on cover slips: gametes were suspended in 6‐well plates filled with artificial seawater, and cover slips were placed on the well bottoms. The gametes settled on the cover slips as spherical cells (1‐cell S phase). These cells grew into larger cells, losing their eyespot (1‐cell L phase), and developed into multicellular thalli. Gene introduction using the polyethylene glycol ( PEG ) method is available with transformation efficiencies of 9.0–15.1%. Transformation was performed using a plasmid encoding green fluorescent protein ( GFP ) fused to the mitochondrial targeting sequence, and mitochondria were labeled by GFP fluorescence. This revealed a string‐shaped giant mitochondrion in a cell of the 1‐cell S phase. In the 1‐cell L phase, a reticular mitochondrion was observed. After the initiation of cell division, the reticular mitochondrion was fragmented, and small oval mitochondria were observed in the 5‐cell phase.