title: Dynamic aspects of spermiogenic chromatin condensation patterning by phase separation during the histone-to-protamine transition in charalean algae and relation to bryophytes.
abstract: During early-to-middle spermiogenesis in multicellular, internally fertilizing charalean green algae (Chara fibrosa, Chara vulgaris, Chara tomentosa, Nitella missouriensis), patterning of chromatin/nucleoplasm in developing spermatid nuclei changes from granules → fibers → contorted lamellae → condensed chromatin. Cytochemical, immunocytochemical, electrophoretic studies on C. vulgaris and C. tomentosa spermatids (Kwiatkowska, Poplonska) and amino acid analysis of protamines in Chara corallina sperm (Reynolds, Wolfe), indicate that more positively charged protamines replace histones directly during spermiogenesis, not indirectly through other intermediate transitional proteins as in internally fertilizing neogastropods and sharks with more ordered spermatid lamellae. We hypothesize that such lamellar-mediated patterning is due to liquid-liquid phase separation by spinodal decomposition. This is a spontaneous thermodynamic process that involves diffusive instability of a lamellar chromatin network, a dominant pattern repeat distance and bicontinuity of chromatin/nucleoplasm phases. C. vulgaris sperm show contorted lamellae in the posterior region, whereas C. corallina sperm display contorted peripheral lamellae and interior fibrils. Among internally fertilizing liverworts, which may have evolved from Zygnematales, mid-spermatid nuclei lack lamellae. Instead they display self-coiled chromatin rods in Blasia pusilla, contain short chromatin tubules in Haplomitrium hookeri resembling those in internally fertilizing mosses and a hornwort and indirectly replace histones with protamines in Marchantia polymorpha.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4. Electronic address: kasinsky@zoology.ubc.ca.
authors.forename: H E
authors.initials: HE
authors.lastname: Kasinsky
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: S
authors.initials: S
authors.lastname: Ellis
authors.affiliation: BioImaging Facility and Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: G
authors.initials: G
authors.lastname: Martens
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada V8W 3P6.
authors.forename: J
authors.initials: J
authors.lastname: Ausió
mesh_terms: D044002:Bryophyta / Q000254:growth & development / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D000460:Chlorophyta / Q000235:genetics / Q000254:growth & development; D002843:Chromatin / Q000235:genetics; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D011479:Protamines / Q000235:genetics / Q000378:metabolism*; D013091:Spermatogenesis; D013816:Thermodynamics
chemical_list: D002843:Chromatin; D006657:Histones; D011479:Protamines
keywords: Bryophytes; Chara; Chromatin patterning; Spermiogenesis; Spinodal